t 48 weeks of treatment, the frequency of pediatric patients with any bleeding adverse reactions was 7.5%. No drug related serious bleeding adverse reaction was reported. The most frequent bleeding adverse reaction was epistaxis (3.7%). No other bleeding adverse reaction was reported in frequency of >1%. Additional trial follow-up through 100 weeks showed a cumulative 12% frequency of any bleeding adverse reaction.
7 DRUG INTERACTIONS
See also Contraindications (4.2), Warnings and Precautions (5.3), and Clinical Pharmacology (12.3).
7.1 Potential for APTIVUS/ritonavir to Affect Other Drugs
APTIVUS co-administered with ritonavir at the recommended dose is a net inhibitor of CYP 3A and may increase plasma concentrations of agents that are primarily metabolized by CYP 3A. Thus, co-administration of APTIVUS/ritonavir with drugs highly dependent on CYP 3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events is contraindicated [see Contraindications (4.2)]. Co-administration with other CYP 3A substrates may require a dose adjustment or additional monitoring [see Drug Interactions (7)].
Clinically significant drug-drug interactions of APTIVUS co-administered with ritonavir are summarized in Table 4 below.
A phenotypic cocktail study was conducted with 16 healthy volunteers to quantify the influence of 10 days of APTIVUS/ritonavir capsule administration on the activity of hepatic CYP 1A2 (caffeine), 2C9 (warfarin), 2C19 (omeprazole), 2D6 (dextromethorphan) and the activity of intestinal and hepatic CYP 3A4/5 (midazolam) and P-glycoprotein (P-gp) (digoxin). This study determined the first-dose and steady-state effects of 500 mg of APTIVUS co-administered with 200 mg of ritonavir twice daily in capsule form. APTIVUS oral solution co-administered with ritonavir capsules demonstrated similar effects as APTIVUS capsules co-administrated with ritonavir.
There was no net effect on CYP 2C9 or hepatic P-gp at first dose or steady state. There was no net effect after first dose on CYP 1A2, but there was moderate induction at steady state. There was modest inhibition of CYP 2C19 at the first dose, but there was marked induction at steady state. Potent inhibition of CYP 2D6 and both hepatic and intestinal CYP 3A4/5 activities were observed after first dose and steady state.
Intestinal and hepatic P-gp activity was assessed by administering oral and intravenous digoxin, respectively. The digoxin results indicate P-gp was inhibited after the first dose of APTIVUS/ritonavir followed by induction of P-gp over time. Thus, it is difficult to predict the net effect of APTIVUS administered with ritonavir on oral bioavailability and plasma concentrations of drugs that are dual substrates of CYP 3A and P-gp. The net effect will vary depending on the relative affinity of the co-administered drugs for CYP 3A and P-gp, and the extent of intestinal first-pass metabolism/efflux. An in vitro induction study in human hepatocytes showed an increase in UGT1A1 by tipranavir similar to that evoked by rifampin. The clinical consequences of this finding have not been established.
7.2 Potential for Other Drugs to Affect Tipranavir
Tipranavir is a CYP 3A substrate and a P-gp substrate. Co-administration of APTIVUS/ritonavir and drugs that induce CYP 3A and/or P-gp may decrease t
