Distribution
Following parenteral administration naloxone is rapidly distributed in the body and readily crosses the placenta. Plasma protein binding occurs but is relatively weak. Plasma albumin is the major binding constituent but significant binding of naloxone also occurs to plasma constituents other than albumin. It is not known whether naloxone is excreted into human milk.
Metabolism and Elimination
Naloxone is metabolized in the liver primarily by glucuronide conjugation with naloxone-3-glucuronide as the major metabolite. In one study, the serum half-life in adults ranged from 30 to 81 minutes (mean 64 ± 12 minutes). In a neonatal study, the mean plasma half-life was observed to be 3.1 ± 0.5 hours. After an oral or intravenous dose, about 25 to 40% of the drug is excreted as metabolites in urine within 6 hours, about 50% in 24 hours, and 60 to 70% in 72 hours.
Distribution
Following parenteral administration naloxone is rapidly distributed in the body and readily crosses the placenta. Plasma protein binding occurs but is relatively weak. Plasma albumin is the major binding constituent but significant binding of naloxone also occurs to plasma constituents other than albumin. It is not known whether naloxone is excreted into human milk.
Metabolism and Elimination
Naloxone is metabolized in the liver primarily by glucuronide conjugation with naloxone-3-glucuronide as the major metabolite. In one study, the serum half-life in adults ranged from 30 to 81 minutes (mean 64 ± 12 minutes). In a neonatal study, the mean plasma half-life was observed to be 3.1 ± 0.5 hours. After an oral or intravenous dose, about 25 to 40% of the drug is excreted as metabolites in urine within 6 hours, about 50% in 24 hours, and 60 to 70% in 72 hours.
Chat online with Pfizer Medical Information regarding your inquiry on a Pfizer medicine.
*Speak with a Pfizer Medical Information Professional regarding your medical inquiry. Available 9AM-5PM ET Monday to Friday; excluding holidays.
Submit a medical question for Pfizer prescription products.
Pfizer Safety
To report an adverse event related to the Pfizer-BioNTech COVID-19 Vaccine, and you are not part of a clinical trial* for this product, click the link below to submit your information:
Pfizer Safety Reporting Site*If you are involved in a clinical trial for this product, adverse events should be reported to your coordinating study site.
If you cannot use the above website, or would like to report an adverse event related to a different Pfizer product, please call Pfizer Safety at (800) 438-1985.
FDA Medwatch
You may also contact the U.S. Food and Drug Administration (FDA) directly to report adverse events or product quality concerns either online at www.fda.gov/medwatch or call (800) 822-7967.