MYCOBUTIN Capsules must not be administered for MAC prophylaxis to patients with active tuberculosis. Patients who develop complaints consistent with active tuberculosis while on prophylaxis with MYCOBUTIN should be evaluated immediately, so that those with active disease may be given an effective combination regimen of anti-tuberculosis medications. Administration of MYCOBUTIN as a single agent to patients with active tuberculosis is likely to lead to the development of tuberculosis that is resistant both to MYCOBUTIN and to rifampin.
There is no evidence that MYCOBUTIN is an effective prophylaxis against M. tuberculosis. Patients requiring prophylaxis against both M. tuberculosis and Mycobacterium avium complex may be given isoniazid and MYCOBUTIN concurrently.
Tuberculosis in HIV-positive patients is common and may present with atypical or extrapulmonary findings. Patients are likely to have a nonreactive purified protein derivative (PPD) despite active disease. In addition to chest X-ray and sputum culture, the following studies may be useful in the diagnosis of tuberculosis in the HIV-positive patient: blood culture, urine culture, or biopsy of a suspicious lymph node.
When MYCOBUTIN is used concomitantly with clarithromycin for MAC treatment, a decreased dose of MYCOBUTIN is recommended due to the increase in plasma concentrations of MYCOBUTIN (see PRECAUTIONS-Drug Interactions, Table 2).
Hypersensitivity reactions may occur in patients receiving rifamycins. Signs and symptoms of these reactions may include hypotension, urticaria, angioedema, acute bronchospasm, conjunctivitis, thrombocytopenia, neutropenia or flu-like syndrome (weakness, fatigue, muscle pain, nausea, vomiting, headache, fever, chills, aches, rash, itching, sweats, dizziness, shortness of breath, chest pain, cough, syncope, palpitations). There have been reports of anaphylaxis with the use of rifamycins.
Monitor patients receiving MYCOBUTIN therapy for signs and/or symptoms of hypersensitivity reactions. If these symptoms occur, administer supportive measures and discontinue MYCOBUTIN.
Due to the possible occurrence of uveitis, patients should also be carefully monitored when MYCOBUTIN is given in combination with clarithromycin (or other macrolides) and/or fluconazole and related compounds (see PRECAUTIONS-Drug Interactions, Table 2). If uveitis is suspected, the patient should be referred to an ophthalmologist and, if considered necessary, treatment with MYCOBUTIN should be suspended (see also ADVERSE REACTIONS).
Clostridioides difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including MYCOBUTIN (rifabutin) Capsules, USP, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibacterial use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibacterial use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibacterial treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.
There have been reports of severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP) associated with MYCOBUTIN (see ADVERSE REACTIONS).
If patients develop a skin rash they should be monitored closely, and MYCOBUTIN discontinued if lesions progress. Specifically, for DRESS, a multi-system potential life-threatening SCAR, time to onset of the first symptoms may be prolonged. DRESS is a clinical diagnosis, and its clinical presentation remains the basis for decision making. An early withdrawal of MYCOBUTIN is essential because of the syndrome's mortality and visceral involvement (e.g., liver, bone marrow or kidney).
Protease inhibitors act as substrates or inhibitors of CYP3A4 mediated metabolism. Therefore, due to significant drug-drug interactions between protease inhibitors and rifabutin, their concomitant use should be based on the overall assessment of the patient and a patient-specific drug profile. The concomitant use of protease inhibitors may require at least a 50% reduction in rifabutin dose, and depending on the protease inhibitor, an adjustment of the antiretroviral drug dose. Increased monitoring for adverse events is recommended when using these drug combinations (see PRECAUTIONS-Drug Interactions).
MYCOBUTIN is a CYP3A inducer. Co-administration with antiretroviral drugs metabolized by CYP3A, including but not limited to products containing bictegravir, elvitegravir, oral rilpivirine, or doravirine and anti-HCV drugs including but not limited to sofosbuvir (alone or in combination) may decrease plasma concentrations of those drugs, which may lead to loss of virologic response and possible development of resistance. Therefore, co-administration with antiretroviral and anti-HCV drugs metabolized by CYP3A is not recommended or there may be a need to increase the dose of antiretroviral or anti-HCV drugs (see PRECAUTIONS-Drug Interactions).
For further recommendations, please refer to the most recent prescribing information of the antiretrovirals or anti-HCV drugs or contact the specific manufacturer.
Because treatment with MYCOBUTIN Capsules may be associated with neutropenia, and more rarely thrombocytopenia, physicians should consider obtaining hematologic studies periodically in patients receiving prophylaxis with MYCOBUTIN.
Patients should be advised of the signs and symptoms of both MAC and tuberculosis, and should be instructed to consult their physicians if they develop new complaints consistent with either of these diseases. In addition, since MYCOBUTIN may rarely be associated with myositis and uveitis, patients should be advised to notify their physicians if they develop signs or symptoms suggesting either of these disorders.
Urine, feces, saliva, sputum, perspiration, tears, and skin may be colored brown-orange with rifabutin and some of its metabolites. Soft contact lenses may be permanently stained. Patients to be treated with MYCOBUTIN should be made aware of these possibilities.
Diarrhea is a common problem caused by antibacterials which usually ends when the antibacterial is discontinued. Sometimes, after starting treatment with antibacterials, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibacterial. If this occurs, patients should contact their physician as soon as possible.
Rifabutin induces CYP3A enzymes and therefore may reduce the plasma concentrations of drugs metabolized by those enzymes. This effect may reduce the efficacy of standard doses of such drugs, which include itraconazole, clarithromycin, and saquinavir.
Some drugs that inhibit CYP3A may significantly increase the plasma concentration of rifabutin. Therefore, carefully monitor for rifabutin associated adverse events in those patients also receiving CYP3A inhibitors, which include fluconazole and clarithromycin. In some cases, the dosage of MYCOBUTIN may need to be reduced when it is co‑administered with CYP3A inhibitors.
Table 2 summarizes the results and magnitude of the pertinent drug interactions assessed with rifabutin. The clinical relevance of these interactions and subsequent dose modifications should be judged in light of the population studied, severity of the disease, patient's drug profile, and the likely impact on the risk/benefit ratio.
| Co‑administered drug | Dosing regimen of co‑administered drug | Dosing regimen of rifabutin | Study population (n) | Effect on rifabutin | Effect on co‑administered drug | Recommendation |
|---|---|---|---|---|---|---|
| ↑ indicates increase; ↓ indicates decrease; ↔ indicates no significant change ND - No Data AUC - Area under the Concentration vs. Time Curve; Cmax - Maximum serum concentration; Cmin – Minimum serum concentration | ||||||
| ||||||
ANTIRETROVIRALS | ||||||
Amprenavir | 1200 mg twice a day for 10 days | 300 mg once a day for 10 days | Healthy male subjects (6) | ↑ AUC by 193%, | ↔ | Reduce rifabutin dose by at least 50%. Monitor closely for adverse reactions. |
Atazanavir/ Ritonavir | 300/100 mg once daily | 150 mg twice weekly | Healthy adult subjects | 48% ↑ in AUC, 149% ↑ Cmax of rifabutin. 990% ↑ in AUC, 677% ↑ Cmax of 25-O‑desacetyl-rifabutin. | No significant change in pharmacokinetics. | A reduction in the dose of rifabutin (to 150 mg every other day or 3 times a week) is recommended. Increased monitoring for adverse reactions is warranted. |
Bictegravir | 75 mg once a day | 300 mg once a day (fasted) | Healthy subjects | ND | ↓ AUC 38% | Co-administration of rifabutin with Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide) is not recommended due to an expected decrease in tenofovir alafenamide in addition to the reported reduction in bictegravir. Refer to Biktarvy prescribing information for additional information. |
Darunavir/Ritonavir | 600/100 mg twice a day for 12 days | 150 mg every other day for 12 days | Healthy HIV- negative adults | No significant change in rifabutin pharmacokinetics. 881% ↑ in AUC, 377% ↑ Cmax of 25-O-desacetyl-rifabutin. | 57% ↑ in AUC, 42% ↑ Cmax of darunavir. 66% ↑ in AUC, 68% ↑ Cmax of ritonavir. | A reduction in the dose of rifabutin (to 150 mg every other day or 3 times a week) is recommended. Increased monitoring for adverse reactions is warranted. |
Delavirdine | 400 mg three times a day | 300 mg once a day | HIV-infected patients (7) | ↑ AUC by 230%, | ↓ AUC by 80%, | CONTRAINDICATED |
Didanosine | 167 or 250 mg twice a day for 12 days | 300 or 600 mg once a day for 12 days | HIV-infected patients (11) | ↔ | ↔ | |
Dolutegravir | 50 mg daily for 14 days | 300 mg daily for 14 days | Healthy adult subjects | ND | No significant change in dolutegravir pharmacokinetics at steady state. | |
Doravirine | 100 mg single dose | 300 mg once a day for 16 days | Healthy subjects (12) | ND | ↓ 50% in AUC, | If concomitant use is necessary, increase the doravirine dosage as instructed in doravirine-containing product prescribing information. |
Elvitegravir/ Cobicistat | 150/50 mg daily | 300 mg daily Or 150 mg every other day | Healthy subjects (12) | No significant change in rifabutin pharmacokinetics. 6.3-fold ↑ in AUC, 4.8-fold ↑ Cmax of 25‑O‑desacetyl-rifabutin. | No change in elvitegravir except 67% ↓ Ctrough of elvitegravir. No change in cobicistat exposure. | Co-administration of rifabutin with elvitegravir/ cobicistat is not recommended due to an expected decrease in elvitegravir exposure. |
Etravirine | 800 mg twice daily for 21 days | 300 mg daily on days 8 to 21 | Healthy volunteers (18) | No significant change in rifabutin pharmacokinetics. | 37% ↓ in AUC, 37% ↓ in Cmax and 35% ↓ in Cmin | No dose adjustment of rifabutin is required when etravirine is not co-administered with protease inhibitor/ritonavir. Rifabutin should not be co-administered with etravirine and boosted PIs due to potential for decreased effectiveness of etravirine. |
Fosamprenavir/ ritonavir | 700 mg twice a day plus ritonavir 100 mg twice a day for 2 weeks | 150 mg every other day for 2 weeks | Healthy subjects (15) | ↔ AUC* | ↑ AUC by 35%†, | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with fosamprenavir/ritonavir combination. |
Indinavir | 800 mg three times a day for 10 days | 300 mg once a day for 10 days | Healthy subjects (10) | ↑ AUC by 173%, | ↓ AUC by 34%, | Reduce rifabutin dose by 50%, and increase indinavir dose from 800 mg to 1000 mg three times a day. |
Lopinavir/ ritonavir | 400/100 mg twice a day for 20 days | 150 mg once a day for 10 days | Healthy subjects (14) | ↑ AUC by 203% ‡ | ↔ | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination. Monitor closely for adverse reactions. Reduce rifabutin dosage further, as needed. |
Saquinavir/ ritonavir | 1000/100 mg twice a day for 14 or 22 days | 150 mg every 3 days for 21–22 days | Healthy subjects | ↑ AUC by 53% § | ↓ AUC by 13%, | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with saquinavir/ritonavir combination. Monitor closely for adverse reactions. |
Rilpivirine | 25 mg once a day | 300 mg once a day | Healthy subjects (18) | ND | ↓ AUC by 42% | Co-administration of rifabutin with Odefsey (rilpivirine/tenofovir alafenamide/emtricitabine) is not recommended, due to an expected decrease in tenofovir alafenamide in addition to the reported reduction in rilpivirine. Refer to Odefsey prescribing information for additional information. Co-administration of rifabutin with cabotegravir/rilpivirine prolonged-release injectable suspension is contraindicated. |
Ritonavir | 500 mg twice a day for 10 days | 150 mg once a day for 16 days | Healthy subjects (5) | ↑ AUC by 300%, | ND | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination. Monitor closely for adverse reactions. |
Tipranavir/ ritonavir | 500/200 twice a day for 15 doses | 150 mg single dose | Healthy subjects (20) | ↑ AUC by 190%, | ↔ | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with tipranavir/ritonavir combination. Monitor closely for adverse reactions. Reduce rifabutin dosage further, as needed. |
Nelfinavir | 1250 mg twice a day for 7–8 days | 150 mg once a day for 8 days | HIV-infected patients (11) | ↑ AUC by 83%, ¶ | ↔ | Reduce rifabutin dose by 50% (to 150 mg once a day) and increase the nelfinavir dose to 1250 mg twice a day. |
Zidovudine | 100 or 200 mg every four hours | 300 or 450 mg once a day | HIV-infected patients (16) | ↔ | ↓ AUC by 32%, | Because zidovudine levels remained within the therapeutic range during co-administration of rifabutin, dosage adjustments are not necessary. |
ANTI-HCV DRUGS | ||||||
Sofosbuvir | 400 mg on day 1 and day 21 | 300 mg daily on day 10 to day 29 | Healthy subjects (20) | ND | 36% ↓ in Cmax and 24% ↓ AUC | Co-administration of rifabutin with sofosbuvir (alone or in combination) is not recommended. |
ANTIFUNGALS | ||||||
Fluconazole | 200 mg once a day for 2 weeks | 300 mg once a day for 2 weeks | HIV-infected patients (12) | ↑ AUC by 82%, | ↔ | Monitor for rifabutin associated adverse events. Reduce rifabutin dose or suspend MYCOBUTIN use if toxicity is suspected. |
Posaconazole | 200 mg once a day for 10 days | 300 mg once a day for 17 days | Healthy subjects (8) | ↑ AUC by 72%, | ↓ AUC by 49%, | If co-administration of these two drugs cannot be avoided, patients should be monitored for adverse events associated with rifabutin administration, and lack of posaconazole efficacy. |
Itraconazole | 200 mg once a day | 300 mg once a day | HIV-Infected patients (6) | ↑# | ↓ AUC by 70%, | If co-administration of these two drugs cannot be avoided, patients should be monitored for adverse events associated with rifabutin administration, and lack of itraconazole efficacy. In a separate study, one case of uveitis was associated with increased serum rifabutin levels following co-administration of rifabutin (300 mg once a day) with itraconazole (600–900 mg once a day). |
Voriconazole | 400 mg twice a day for 7 days (maintenance dose) | 300 mg once a day for 7 days | Healthy male subjects (12) | ↑ AUC by 331%, | ↑ AUC by ~100%, | CONTRAINDICATED |
ANTI-PCP (Pneumocystis carinii pneumonia) | ||||||
Dapsone | 50 mg once a day | 300 mg once a day | HIV-infected patients (16) | ND | ↓ AUC by 27–40% | |
Sulfamethoxazole-Trimethoprim | 800/160 mg | 300 mg once a day | HIV-infected patients (12) | ↔ | ↓ AUC by 15–20% | |
ANTI-MAC (Mycobacterium avium intracellulare complex) | ||||||
Azithromycin | 500 mg once a day for 1 day, then 250 mg once a day for 9 days | 300 mg once a day | Healthy subjects (6) | ↔ | ↔ | |
Clarithromycin | 500 mg twice a day | 300 mg once a day | HIV-infected patients (12) | ↑ AUC by 75% | ↓ AUC by 50% | Monitor for rifabutin associated adverse events. Reduce dose or suspend use of MYCOBUTIN if toxicity is suspected. Alternative treatment for clarithromycin should be considered when treating patients receiving rifabutin |
ANTI-TB (Tuberculosis) | ||||||
Ethambutol | 1200 mg | 300 mg once a day for 7 days | Healthy subjects (10) | ND | ↔ | |
Isoniazid | 300 mg | 300 mg once a day for 7 days | Healthy subjects (6) | ND | ↔ | |
Bedaquiline | 400 mg daily on day 1 and day 29 | 300 mg daily | Healthy subjects (17) | ND | No change in bedaquiline pharmacokinetics. 1.4-fold ↑ in M2 and approximately 3.0-fold ↑ in M3 metabolites of bedaquiline. | Avoid bedaquiline co-administration with rifabutin due to the adverse reactions associated with increased bedaquiline metabolite concentrations. |
OTHER | ||||||
Methadone | 20 – 100 mg once a day | 300 mg once a day for 13 days | HIV-infected patients (24) | ND | ↔ | |
Ethinylestradiol (EE)/Norethindrone (NE) | 35 mg EE / 1 mg NE for 21 days | 300 mg once a day for 10 days | Healthy female subjects (22) | ND | EE: ↓ AUC by | Patients should be advised to use additional or alternative methods of contraception. |
Theophylline | 5 mg/kg | 300 mg for 14 days | Healthy subjects (11) | ND | ↔ | |
Long-term carcinogenicity studies were conducted with rifabutin in mice and in rats. Rifabutin was not carcinogenic in mice at doses up to 180 mg/kg/day, or approximately 36 times the recommended human daily dose. Rifabutin was not carcinogenic in the rat at doses up to 60 mg/kg/day, about 12 times the recommended human dose.
Rifabutin was not mutagenic in the bacterial mutation assay (Ames Test) using both rifabutin-susceptible and resistant strains. Rifabutin was not mutagenic in Schizosaccharomyces pombe P1 and was not genotoxic in V-79 Chinese hamster cells, human lymphocytes in vitro, or mouse bone marrow cells in vivo.
Fertility was impaired in male rats given 160 mg/kg (32 times the recommended human daily dose).
Rifabutin should be used in pregnant women only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant or breastfeeding women.
Reproduction studies have been carried out in rats and rabbits given rifabutin using dose levels up to 200 mg/kg (about 6 to 13 times the recommended human daily dose based on body surface area comparisons). No teratogenicity was observed in either species. In rats, given 200 mg/kg/day, (about 6 times the recommended human daily dose based on body surface area comparisons), there was a decrease in fetal viability. In rats, at 40 mg/kg/day (approximately equivalent to the recommended human daily dose based on body surface area comparisons), rifabutin caused an increase in fetal skeletal variants. In rabbits, at 80 mg/kg/day (about 5 times the recommended human daily dose based on body surface area comparisons), rifabutin caused maternotoxicity and increase in fetal skeletal anomalies. Because animal reproduction studies are not always predictive of human response, rifabutin should be used in pregnant women only if the potential benefit justifies the potential risk to the fetus.
It is not known whether rifabutin is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness of rifabutin for prophylaxis of MAC in children have not been established. Limited safety data are available from treatment use in 22 HIV-positive children with MAC who received MYCOBUTIN in combination with at least two other antimycobacterials for periods from 1 to 183 weeks. Mean doses (mg/kg) for these children were: 18.5 (range 15.0 to 25.0) for infants 1 year of age, 8.6 (range 4.4 to 18.8) for children 2 to 10 years of age, and 4.0 (range 2.8 to 5.4) for adolescents 14 to 16 years of age. There is no evidence that doses greater than 5 mg/kg daily are useful. Adverse experiences were similar to those observed in the adult population, and included leukopenia, neutropenia, and rash. In addition, corneal deposits have been observed in some patients during routine ophthalmologic surveillance of HIV-positive pediatric patients receiving MYCOBUTIN as part of a multiple-drug regimen for MAC prophylaxis. These are tiny, almost transparent, asymptomatic peripheral and central corneal deposits which do not impair vision.
Clinical studies of MYCOBUTIN did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy (see CLINICAL PHARMACOLOGY).
MYCOBUTIN Capsules must not be administered for MAC prophylaxis to patients with active tuberculosis. Patients who develop complaints consistent with active tuberculosis while on prophylaxis with MYCOBUTIN should be evaluated immediately, so that those with active disease may be given an effective combination regimen of anti-tuberculosis medications. Administration of MYCOBUTIN as a single agent to patients with active tuberculosis is likely to lead to the development of tuberculosis that is resistant both to MYCOBUTIN and to rifampin.
There is no evidence that MYCOBUTIN is an effective prophylaxis against M. tuberculosis. Patients requiring prophylaxis against both M. tuberculosis and Mycobacterium avium complex may be given isoniazid and MYCOBUTIN concurrently.
Tuberculosis in HIV-positive patients is common and may present with atypical or extrapulmonary findings. Patients are likely to have a nonreactive purified protein derivative (PPD) despite active disease. In addition to chest X-ray and sputum culture, the following studies may be useful in the diagnosis of tuberculosis in the HIV-positive patient: blood culture, urine culture, or biopsy of a suspicious lymph node.
When MYCOBUTIN is used concomitantly with clarithromycin for MAC treatment, a decreased dose of MYCOBUTIN is recommended due to the increase in plasma concentrations of MYCOBUTIN (see PRECAUTIONS-Drug Interactions, Table 2).
Hypersensitivity reactions may occur in patients receiving rifamycins. Signs and symptoms of these reactions may include hypotension, urticaria, angioedema, acute bronchospasm, conjunctivitis, thrombocytopenia, neutropenia or flu-like syndrome (weakness, fatigue, muscle pain, nausea, vomiting, headache, fever, chills, aches, rash, itching, sweats, dizziness, shortness of breath, chest pain, cough, syncope, palpitations). There have been reports of anaphylaxis with the use of rifamycins.
Monitor patients receiving MYCOBUTIN therapy for signs and/or symptoms of hypersensitivity reactions. If these symptoms occur, administer supportive measures and discontinue MYCOBUTIN.
Due to the possible occurrence of uveitis, patients should also be carefully monitored when MYCOBUTIN is given in combination with clarithromycin (or other macrolides) and/or fluconazole and related compounds (see PRECAUTIONS-Drug Interactions, Table 2). If uveitis is suspected, the patient should be referred to an ophthalmologist and, if considered necessary, treatment with MYCOBUTIN should be suspended (see also ADVERSE REACTIONS).
Clostridioides difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including MYCOBUTIN (rifabutin) Capsules, USP, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibacterial use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibacterial use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibacterial treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.
There have been reports of severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP) associated with MYCOBUTIN (see ADVERSE REACTIONS).
If patients develop a skin rash they should be monitored closely, and MYCOBUTIN discontinued if lesions progress. Specifically, for DRESS, a multi-system potential life-threatening SCAR, time to onset of the first symptoms may be prolonged. DRESS is a clinical diagnosis, and its clinical presentation remains the basis for decision making. An early withdrawal of MYCOBUTIN is essential because of the syndrome's mortality and visceral involvement (e.g., liver, bone marrow or kidney).
Protease inhibitors act as substrates or inhibitors of CYP3A4 mediated metabolism. Therefore, due to significant drug-drug interactions between protease inhibitors and rifabutin, their concomitant use should be based on the overall assessment of the patient and a patient-specific drug profile. The concomitant use of protease inhibitors may require at least a 50% reduction in rifabutin dose, and depending on the protease inhibitor, an adjustment of the antiretroviral drug dose. Increased monitoring for adverse events is recommended when using these drug combinations (see PRECAUTIONS-Drug Interactions).
MYCOBUTIN is a CYP3A inducer. Co-administration with antiretroviral drugs metabolized by CYP3A, including but not limited to products containing bictegravir, elvitegravir, oral rilpivirine, or doravirine and anti-HCV drugs including but not limited to sofosbuvir (alone or in combination) may decrease plasma concentrations of those drugs, which may lead to loss of virologic response and possible development of resistance. Therefore, co-administration with antiretroviral and anti-HCV drugs metabolized by CYP3A is not recommended or there may be a need to increase the dose of antiretroviral or anti-HCV drugs (see PRECAUTIONS-Drug Interactions).
For further recommendations, please refer to the most recent prescribing information of the antiretrovirals or anti-HCV drugs or contact the specific manufacturer.
Because treatment with MYCOBUTIN Capsules may be associated with neutropenia, and more rarely thrombocytopenia, physicians should consider obtaining hematologic studies periodically in patients receiving prophylaxis with MYCOBUTIN.
Patients should be advised of the signs and symptoms of both MAC and tuberculosis, and should be instructed to consult their physicians if they develop new complaints consistent with either of these diseases. In addition, since MYCOBUTIN may rarely be associated with myositis and uveitis, patients should be advised to notify their physicians if they develop signs or symptoms suggesting either of these disorders.
Urine, feces, saliva, sputum, perspiration, tears, and skin may be colored brown-orange with rifabutin and some of its metabolites. Soft contact lenses may be permanently stained. Patients to be treated with MYCOBUTIN should be made aware of these possibilities.
Diarrhea is a common problem caused by antibacterials which usually ends when the antibacterial is discontinued. Sometimes, after starting treatment with antibacterials, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibacterial. If this occurs, patients should contact their physician as soon as possible.
Rifabutin induces CYP3A enzymes and therefore may reduce the plasma concentrations of drugs metabolized by those enzymes. This effect may reduce the efficacy of standard doses of such drugs, which include itraconazole, clarithromycin, and saquinavir.
Some drugs that inhibit CYP3A may significantly increase the plasma concentration of rifabutin. Therefore, carefully monitor for rifabutin associated adverse events in those patients also receiving CYP3A inhibitors, which include fluconazole and clarithromycin. In some cases, the dosage of MYCOBUTIN may need to be reduced when it is co‑administered with CYP3A inhibitors.
Table 2 summarizes the results and magnitude of the pertinent drug interactions assessed with rifabutin. The clinical relevance of these interactions and subsequent dose modifications should be judged in light of the population studied, severity of the disease, patient's drug profile, and the likely impact on the risk/benefit ratio.
| Co‑administered drug | Dosing regimen of co‑administered drug | Dosing regimen of rifabutin | Study population (n) | Effect on rifabutin | Effect on co‑administered drug | Recommendation |
|---|---|---|---|---|---|---|
| ↑ indicates increase; ↓ indicates decrease; ↔ indicates no significant change ND - No Data AUC - Area under the Concentration vs. Time Curve; Cmax - Maximum serum concentration; Cmin – Minimum serum concentration | ||||||
| ||||||
ANTIRETROVIRALS | ||||||
Amprenavir | 1200 mg twice a day for 10 days | 300 mg once a day for 10 days | Healthy male subjects (6) | ↑ AUC by 193%, | ↔ | Reduce rifabutin dose by at least 50%. Monitor closely for adverse reactions. |
Atazanavir/ Ritonavir | 300/100 mg once daily | 150 mg twice weekly | Healthy adult subjects | 48% ↑ in AUC, 149% ↑ Cmax of rifabutin. 990% ↑ in AUC, 677% ↑ Cmax of 25-O‑desacetyl-rifabutin. | No significant change in pharmacokinetics. | A reduction in the dose of rifabutin (to 150 mg every other day or 3 times a week) is recommended. Increased monitoring for adverse reactions is warranted. |
Bictegravir | 75 mg once a day | 300 mg once a day (fasted) | Healthy subjects | ND | ↓ AUC 38% | Co-administration of rifabutin with Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide) is not recommended due to an expected decrease in tenofovir alafenamide in addition to the reported reduction in bictegravir. Refer to Biktarvy prescribing information for additional information. |
Darunavir/Ritonavir | 600/100 mg twice a day for 12 days | 150 mg every other day for 12 days | Healthy HIV- negative adults | No significant change in rifabutin pharmacokinetics. 881% ↑ in AUC, 377% ↑ Cmax of 25-O-desacetyl-rifabutin. | 57% ↑ in AUC, 42% ↑ Cmax of darunavir. 66% ↑ in AUC, 68% ↑ Cmax of ritonavir. | A reduction in the dose of rifabutin (to 150 mg every other day or 3 times a week) is recommended. Increased monitoring for adverse reactions is warranted. |
Delavirdine | 400 mg three times a day | 300 mg once a day | HIV-infected patients (7) | ↑ AUC by 230%, | ↓ AUC by 80%, | CONTRAINDICATED |
Didanosine | 167 or 250 mg twice a day for 12 days | 300 or 600 mg once a day for 12 days | HIV-infected patients (11) | ↔ | ↔ | |
Dolutegravir | 50 mg daily for 14 days | 300 mg daily for 14 days | Healthy adult subjects | ND | No significant change in dolutegravir pharmacokinetics at steady state. | |
Doravirine | 100 mg single dose | 300 mg once a day for 16 days | Healthy subjects (12) | ND | ↓ 50% in AUC, | If concomitant use is necessary, increase the doravirine dosage as instructed in doravirine-containing product prescribing information. |
Elvitegravir/ Cobicistat | 150/50 mg daily | 300 mg daily Or 150 mg every other day | Healthy subjects (12) | No significant change in rifabutin pharmacokinetics. 6.3-fold ↑ in AUC, 4.8-fold ↑ Cmax of 25‑O‑desacetyl-rifabutin. | No change in elvitegravir except 67% ↓ Ctrough of elvitegravir. No change in cobicistat exposure. | Co-administration of rifabutin with elvitegravir/ cobicistat is not recommended due to an expected decrease in elvitegravir exposure. |
Etravirine | 800 mg twice daily for 21 days | 300 mg daily on days 8 to 21 | Healthy volunteers (18) | No significant change in rifabutin pharmacokinetics. | 37% ↓ in AUC, 37% ↓ in Cmax and 35% ↓ in Cmin | No dose adjustment of rifabutin is required when etravirine is not co-administered with protease inhibitor/ritonavir. Rifabutin should not be co-administered with etravirine and boosted PIs due to potential for decreased effectiveness of etravirine. |
Fosamprenavir/ ritonavir | 700 mg twice a day plus ritonavir 100 mg twice a day for 2 weeks | 150 mg every other day for 2 weeks | Healthy subjects (15) | ↔ AUC* | ↑ AUC by 35%†, | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with fosamprenavir/ritonavir combination. |
Indinavir | 800 mg three times a day for 10 days | 300 mg once a day for 10 days | Healthy subjects (10) | ↑ AUC by 173%, | ↓ AUC by 34%, | Reduce rifabutin dose by 50%, and increase indinavir dose from 800 mg to 1000 mg three times a day. |
Lopinavir/ ritonavir | 400/100 mg twice a day for 20 days | 150 mg once a day for 10 days | Healthy subjects (14) | ↑ AUC by 203% ‡ | ↔ | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination. Monitor closely for adverse reactions. Reduce rifabutin dosage further, as needed. |
Saquinavir/ ritonavir | 1000/100 mg twice a day for 14 or 22 days | 150 mg every 3 days for 21–22 days | Healthy subjects | ↑ AUC by 53% § | ↓ AUC by 13%, | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with saquinavir/ritonavir combination. Monitor closely for adverse reactions. |
Rilpivirine | 25 mg once a day | 300 mg once a day | Healthy subjects (18) | ND | ↓ AUC by 42% | Co-administration of rifabutin with Odefsey (rilpivirine/tenofovir alafenamide/emtricitabine) is not recommended, due to an expected decrease in tenofovir alafenamide in addition to the reported reduction in rilpivirine. Refer to Odefsey prescribing information for additional information. Co-administration of rifabutin with cabotegravir/rilpivirine prolonged-release injectable suspension is contraindicated. |
Ritonavir | 500 mg twice a day for 10 days | 150 mg once a day for 16 days | Healthy subjects (5) | ↑ AUC by 300%, | ND | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination. Monitor closely for adverse reactions. |
Tipranavir/ ritonavir | 500/200 twice a day for 15 doses | 150 mg single dose | Healthy subjects (20) | ↑ AUC by 190%, | ↔ | Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with tipranavir/ritonavir combination. Monitor closely for adverse reactions. Reduce rifabutin dosage further, as needed. |
Nelfinavir | 1250 mg twice a day for 7–8 days | 150 mg once a day for 8 days | HIV-infected patients (11) | ↑ AUC by 83%, ¶ | ↔ | Reduce rifabutin dose by 50% (to 150 mg once a day) and increase the nelfinavir dose to 1250 mg twice a day. |
Zidovudine | 100 or 200 mg every four hours | 300 or 450 mg once a day | HIV-infected patients (16) | ↔ | ↓ AUC by 32%, | Because zidovudine levels remained within the therapeutic range during co-administration of rifabutin, dosage adjustments are not necessary. |
ANTI-HCV DRUGS | ||||||
Sofosbuvir | 400 mg on day 1 and day 21 | 300 mg daily on day 10 to day 29 | Healthy subjects (20) | ND | 36% ↓ in Cmax and 24% ↓ AUC | Co-administration of rifabutin with sofosbuvir (alone or in combination) is not recommended. |
ANTIFUNGALS | ||||||
Fluconazole | 200 mg once a day for 2 weeks | 300 mg once a day for 2 weeks | HIV-infected patients (12) | ↑ AUC by 82%, | ↔ | Monitor for rifabutin associated adverse events. Reduce rifabutin dose or suspend MYCOBUTIN use if toxicity is suspected. |
Posaconazole | 200 mg once a day for 10 days | 300 mg once a day for 17 days | Healthy subjects (8) | ↑ AUC by 72%, | ↓ AUC by 49%, | If co-administration of these two drugs cannot be avoided, patients should be monitored for adverse events associated with rifabutin administration, and lack of posaconazole efficacy. |
Itraconazole | 200 mg once a day | 300 mg once a day | HIV-Infected patients (6) | ↑# | ↓ AUC by 70%, | If co-administration of these two drugs cannot be avoided, patients should be monitored for adverse events associated with rifabutin administration, and lack of itraconazole efficacy. In a separate study, one case of uveitis was associated with increased serum rifabutin levels following co-administration of rifabutin (300 mg once a day) with itraconazole (600–900 mg once a day). |
Voriconazole | 400 mg twice a day for 7 days (maintenance dose) | 300 mg once a day for 7 days | Healthy male subjects (12) | ↑ AUC by 331%, | ↑ AUC by ~100%, | CONTRAINDICATED |
ANTI-PCP (Pneumocystis carinii pneumonia) | ||||||
Dapsone | 50 mg once a day | 300 mg once a day | HIV-infected patients (16) | ND | ↓ AUC by 27–40% | |
Sulfamethoxazole-Trimethoprim | 800/160 mg | 300 mg once a day | HIV-infected patients (12) | ↔ | ↓ AUC by 15–20% | |
ANTI-MAC (Mycobacterium avium intracellulare complex) | ||||||
Azithromycin | 500 mg once a day for 1 day, then 250 mg once a day for 9 days | 300 mg once a day | Healthy subjects (6) | ↔ | ↔ | |
Clarithromycin | 500 mg twice a day | 300 mg once a day | HIV-infected patients (12) | ↑ AUC by 75% | ↓ AUC by 50% | Monitor for rifabutin associated adverse events. Reduce dose or suspend use of MYCOBUTIN if toxicity is suspected. Alternative treatment for clarithromycin should be considered when treating patients receiving rifabutin |
ANTI-TB (Tuberculosis) | ||||||
Ethambutol | 1200 mg | 300 mg once a day for 7 days | Healthy subjects (10) | ND | ↔ | |
Isoniazid | 300 mg | 300 mg once a day for 7 days | Healthy subjects (6) | ND | ↔ | |
Bedaquiline | 400 mg daily on day 1 and day 29 | 300 mg daily | Healthy subjects (17) | ND | No change in bedaquiline pharmacokinetics. 1.4-fold ↑ in M2 and approximately 3.0-fold ↑ in M3 metabolites of bedaquiline. | Avoid bedaquiline co-administration with rifabutin due to the adverse reactions associated with increased bedaquiline metabolite concentrations. |
OTHER | ||||||
Methadone | 20 – 100 mg once a day | 300 mg once a day for 13 days | HIV-infected patients (24) | ND | ↔ | |
Ethinylestradiol (EE)/Norethindrone (NE) | 35 mg EE / 1 mg NE for 21 days | 300 mg once a day for 10 days | Healthy female subjects (22) | ND | EE: ↓ AUC by | Patients should be advised to use additional or alternative methods of contraception. |
Theophylline | 5 mg/kg | 300 mg for 14 days | Healthy subjects (11) | ND | ↔ | |
Long-term carcinogenicity studies were conducted with rifabutin in mice and in rats. Rifabutin was not carcinogenic in mice at doses up to 180 mg/kg/day, or approximately 36 times the recommended human daily dose. Rifabutin was not carcinogenic in the rat at doses up to 60 mg/kg/day, about 12 times the recommended human dose.
Rifabutin was not mutagenic in the bacterial mutation assay (Ames Test) using both rifabutin-susceptible and resistant strains. Rifabutin was not mutagenic in Schizosaccharomyces pombe P1 and was not genotoxic in V-79 Chinese hamster cells, human lymphocytes in vitro, or mouse bone marrow cells in vivo.
Fertility was impaired in male rats given 160 mg/kg (32 times the recommended human daily dose).
Rifabutin should be used in pregnant women only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant or breastfeeding women.
Reproduction studies have been carried out in rats and rabbits given rifabutin using dose levels up to 200 mg/kg (about 6 to 13 times the recommended human daily dose based on body surface area comparisons). No teratogenicity was observed in either species. In rats, given 200 mg/kg/day, (about 6 times the recommended human daily dose based on body surface area comparisons), there was a decrease in fetal viability. In rats, at 40 mg/kg/day (approximately equivalent to the recommended human daily dose based on body surface area comparisons), rifabutin caused an increase in fetal skeletal variants. In rabbits, at 80 mg/kg/day (about 5 times the recommended human daily dose based on body surface area comparisons), rifabutin caused maternotoxicity and increase in fetal skeletal anomalies. Because animal reproduction studies are not always predictive of human response, rifabutin should be used in pregnant women only if the potential benefit justifies the potential risk to the fetus.
It is not known whether rifabutin is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness of rifabutin for prophylaxis of MAC in children have not been established. Limited safety data are available from treatment use in 22 HIV-positive children with MAC who received MYCOBUTIN in combination with at least two other antimycobacterials for periods from 1 to 183 weeks. Mean doses (mg/kg) for these children were: 18.5 (range 15.0 to 25.0) for infants 1 year of age, 8.6 (range 4.4 to 18.8) for children 2 to 10 years of age, and 4.0 (range 2.8 to 5.4) for adolescents 14 to 16 years of age. There is no evidence that doses greater than 5 mg/kg daily are useful. Adverse experiences were similar to those observed in the adult population, and included leukopenia, neutropenia, and rash. In addition, corneal deposits have been observed in some patients during routine ophthalmologic surveillance of HIV-positive pediatric patients receiving MYCOBUTIN as part of a multiple-drug regimen for MAC prophylaxis. These are tiny, almost transparent, asymptomatic peripheral and central corneal deposits which do not impair vision.
Clinical studies of MYCOBUTIN did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy (see CLINICAL PHARMACOLOGY).
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