Buprenorphine and Fosamprenavir interaction
Buprenorphine and Fosamprenavir: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Buprenorphine (BELBUCA) label · effective 2026-01-02
Evaluate patients starting CYP3A4 inhibitors or stopping CYP3A4 inducers at frequent intervals for respiratory depression.
Inhibitors of CYP3A4 Clinical Impact: The concomitant use of BELBUCA and CYP3A4 inhibitors can increase the plasma concentration of buprenorphine, resulting in increased or prolonged opioid effects, particularly when an inhibitor is added after a stable dose of BELBUCA is achieved.
After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, the buprenorphine plasma concentration will decrease [see Clinical Pharmacology (12.3) ] , potentially resulting in decreased opioid efficacy or a withdrawal syndrome in patients who had developed physical dependence to buprenorphine.
If a CYP3A4 inhibitor is discontinued, consider increasing the BELBUCA dosage until stable drug effects are achieved.
Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir) CYP3A4 Inducers Clinical Impact: The concomitant use of BELBUCA and CYP3A4 inducers can decrease the plasma concentration of buprenorphine [see Clinical Pharmacology (12.3) ] , potentially resulting in decreased efficacy or…
From the Fosamprenavir (Fosamprenavir Calcium) label · effective 2026-06-30
…Hypericum perforatum ) Lipid modifying agents: Lomitapide, lovastatin, simvastatin Non-nucleoside reverse transcriptase inhibitor: Delavirdine PDE5 inhibitor: Sildenafil (Revatio) (for treatment of pulmonary arterial hypertension) Sedative/hypnotics: Midazolam, triazolam Hypersensitivity to fosamprenavir calcium or amprenavir (e.g., Stevens-Johnson syndrome).
Fosamprenavir calcium/ritonavir: ↔ Amprenavir ↔ Esomeprazole Sedative/hypnotics: Midazolam, triazolam ↑Midazolam ↑Triazolam Coadministration is contraindicated due to potential for serious and/or life-threatening reactions such as prolonged or increased sedation or respiratory depression [see Contraindications (4)].
Narcotic analgesic: Methadone Fentanyl ↓ Methadone ↑Fentanyl Data suggest that the interaction is not clinically relevant; however, patients should be monitored for opiate withdrawal symptoms.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.