avir co-administration is likely to result in increased plasma concentrations of alfuzosin and is therefore contraindicated (see section 4.3).
Amphetamine Derivatives
Amphetamine
Ritonavir dosed as an antiretroviral agent is likely to inhibit CYP2D6 and as a result is expected to increase concentrations of amphetamine and its derivatives. Careful monitoring of therapeutic and adverse effects is recommended when these medicines are concomitantly administered with antiretroviral doses of ritonavir (see section 4.4).
Analgesics
Buprenorphine
16 q24h
100 q12h
↑ 57%
↑ 77%
Norbuprenorphine
↑ 33%
↑ 108%
Glucuronide metabolites
↔
↔
The increases of plasma levels of buprenorphine and its active metabolite did not lead to clinically significant pharmacodynamic changes in a population of opioid tolerant patients. Adjustment to the dose of buprenorphine or ritonavir may therefore not be necessary when the two are dosed together. When ritonavir is used in combination with another protease inhibitor and buprenorphine, the SPC of the co-administered protease inhibitor should be reviewed for specific dosing information.
Pethidine, piroxicam, propoxyphene
Ritonavir co-administration is likely to result in increased plasma concentrations of pethidine, piroxicam, and propoxyphene and is therefore contraindicated (see section 4.3).
Fentanyl
Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of fentanyl. Careful monitoring of therapeutic and adverse effects (including respiratory depression) is recommended when fentanyl is concomitantly administered with ritonavir.
Methadone1
5, single dose
500 q12h,
36%
38%
Increased methadone dose may be necessary when concomitantly administered with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer due to induction of glucuronidation. Dose adjustment should be considered based on the patient's clinical response to methadone therapy.
Morphine
Morphine levels may be decreased due to induction of glucuronidation by co-administered ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer.
Antiarrthymics
Amiodarone, bepridil, encainide, flecanide, propafenone, quinidine
Ritonavir co-administration is likely to result in increased plasma concentrations of amiodarone, bepridil, encainide, flecanide, propafenone, and quinidine and is therefore contraindicated (see section 4.3).
Digoxin
0.5 single IV dose
300 q12h, 3 days
↑ 86%
ND
0.4 single oral dose
200 q12h, 13 days
↑ 22%
↔
This interaction may be due to modification of P-glycoprotein mediated digoxin efflux by ritonavir dosed as an antriretroviral agent or as a pharmacokinetic enhancer. Increased digoxin levels observed in patients receiving ritonavir may lessen over time as induction develops (see section 4.4).
Antiasthmatic
Theophylline1
3 mg/kg q8h
500 q12h
43%
32%
An increased dose of theophyline may be required when co-adm |
