Fosamprenavir and Methadose (Methadone Tablets)

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Using methadone together with fosamprenavir may decrease the effects of both medications. Contact your doctor if your condition changes or if you experience restlessness, insomnia, sweating, increased tears, or runny nose. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

MONITOR: Coadministration with fosamprenavir alone or in combination with low-dose ritonavir may decrease the plasma concentrations of methadone. The exact mechanism of interaction has not been described. In 16 study subjects treated with methadone (44 to 100 mg daily for at least 30 days) and amprenavir (1200 mg twice a day for 10 days), mean peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) of the pharmacologically active R(+) enantiomer of methadone were reduced by 25%, 13% and 21%, respectively, compared to administration of methadone alone. Similarly, in 19 study subjects administered methadone (70 mg to 120 mg once a day) in combination with fosamprenavir/ritonavir (700 mg/100 mg twice a day) for two weeks, Cmax, AUC and Cmin of R(+) methadone decreased by 21%, 18% and 11%, respectively.

GENERALLY AVOID: Methadone may decrease the plasma concentrations of amprenavir in the absence of low-dose ritonavir as a pharmacokinetic booster. In 16 study subjects treated with methadone (44 to 100 mg daily for at least 30 days) and amprenavir (1200 mg twice a day for 10 days), mean serum amprenavir Cmax, AUC and Cmin were reduced by 27%, 30% and 25%, respectively, compared to a non-matched historical control group. The clinical significance of these changes is unknown. In contrast, the pharmacokinetics of amprenavir administered as fosamprenavir/ritonavir were not altered by methadone when compared to historical control data.

MANAGEMENT: Based on available pharmacokinetic data, the interaction between methadone and fosamprenavir/ritonavir is not expected to be clinically significant. However, as a precaution, patients should be monitored for opiate withdrawal symptoms if prescribed fosamprenavir/ritonavir while receiving methadone treatment. Patients should be advised to notify their caregiver if they experience symptoms of methadone withdrawal such as restlessness, insomnia, sweating, lacrimation, or rhinorrhea. Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, fosamprenavir should preferably not be used with methadone in the absence of ritonavir as a pharmacokinetic booster.

Fosamprenavir

Generic Name: fosamprenavir

Brand name: Lexiva, Telzir

Synonyms: n.a.

What is Fosamprenavir?

Methadose (Methadone Tablets)

Generic Name: methadone

Brand name: Methadose, Dolophine, Methadose Sugar-Free, Diskets

Synonyms: Methadose (Oral Concentrate), Methadose

What is Methadose (Methadone Tablets)?