Lamivudine and tenofovir disoproxil

7 DRUG INTERACTIONS • Atazanavir: Atazanavir should be coadministered with ritonavir when coadministered with CIMDUO. ( 7.2 ) • HIV-1 Protease Inhibitors: Monitor for evidence of tenofovir toxicity when CIMDUO is coadministrated with atazanavir/ritonavir, darunavir/ritonavir, or lopinavir/ritonavir. ( 7.2 ) • Sorbitol: Avoid chronic administration of sorbitol with CIMDUO.( 7.5 )

7.1 Drugs Affecting Renal Function Since tenofovir is primarily eliminated by the kidneys [see Clinical Pharmacology (12.3) ] , coadministration of CIMDUO with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of tenofovir and/or increase the concentrations of other renally eliminated drugs. Some examples include, but are not limited to cidofovir, acyclovir, valacyclovir, ganciclovir, valganciclovir, aminoglycosides (e.g., gentamicin), and high-dose or multiple NSAIDs [see Warnings and Precautions (5.3) ] .

7.2 HIV-1 Protease Inhibitors TDF decreases the AUC and C min of atazanavir [see Clinical Pharmacology (12.3) ] . When coadministered with CIMDUO, it is recommended that atazanavir 300 mg is given with ritonavir 100 mg. TDF should not be coadministered with atazanavir without ritonavir. Lopinavir/ritonavir, atazanavir coadministered with ritonavir, and darunavir coadministered with ritonavir have been shown to increase tenofovir concentrations [see Clinical Pharmacology (12.3) ] . Patients receiving CIMDUO concomitantly with lopinavir/ritonavir, atazanavir and ritonavir, or darunavir and ritonavir should be monitored for tenofovir-associated adverse reactions.

CIMDUO should be discontinued in patients who develop tenofovir-associated adverse reactions.

7.3 Hepatitis C Antiviral Agents Coadministration of TDF, a component of CIMDUO, and EPCLUSA ® (sofosbuvir/velpatasvir) or HARVONI ® (ledipasvir/sofosbuvir) has been shown to increase tenofovir exposure [see Clinical Pharmacology (12.3) ] . In patients receiving TDF concomitantly with sofosbuvir/velpatasvir, monitor for adverse reactions associated with TDF. In patients receiving CIMDUO concomitantly with ledipasvir/sofosbuvir without an HIV-1 protease inhibitor/ritonavir or an HIV-1 protease inhibitor/cobicistat combination, monitor for adverse reactions associated with tenofovir.

In patients receiving CIMDUO concomitantly with ledipasvir/sofosbuvir and an HIV-1 protease inhibitor/ritonavir or an HIV-1 protease inhibitor/cobicistat combination, consider an alternative HCV or antiretroviral therapy, as the safety of increased tenofovir concentrations in this setting has not been established. If coadministration is necessary, monitor for adverse reactions associated with tenofovir.

7.4 Drugs Inhibiting Organic Cation Transporters 3TC, a component of CIMDUO, is predominantly eliminated in the urine by active organic cationic secretion. The possibility of interactions with other drugs administered concurrently should be considered, particularly when their main route of elimination is active renal secretion via the organic cationic transport system (e.g., trimethoprim) [see Clinical Pharmacology (12.3) ] . No data are available regarding interactions with other drugs that have renal clearance mechanisms similar to that of 3TC.

7.5 Sorbitol Coadministration of single doses of 3TC and sorbitol resulted in a sorbitol dose-dependent reduction in 3TC exposures. When possible, avoid use of sorbitol-containing medicines with 3TC [see Clinical Pharmacology (12.3) ] .

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to CIMDUO during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263. Risk Summary Available data from the APR show no difference in the risk of overall major birth defects for 3TC compared to the background rate for major birth defects of 2.7% in the U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP) (see Data ) . 3TC produced embryonic toxicity in rabbits at a dose that produced similar human exposures as the recommended clinical dose.

The relevance of animal findings to human pregnancy registry data is not known. There are no adequate and well-controlled studies with TDF in pregnant women. Because animal reproduction studies are not always predictive of human response, TDF should be used during pregnancy only if clearly needed. Human Data Lamivudine Based on prospective reports from the APR of over 11,000 exposures to 3TC during pregnancy resulting in live births (including over 4,300 exposed in the first trimester), there was no difference between 3TC and overall birth defects compared with the background birth defect rate of 2.7% in the U.S. reference population of the MACDP.

The prevalence of defects in the first trimester was 3.1% (95% CI: 2.6% to 3.7%). 3TC pharmacokinetics were studied in pregnant women during 2 clinical trials conducted in South Africa. The trials assessed pharmacokinetics in 16 women at 36 weeks gestation using 150 mg 3TC twice daily with zidovudine, 10 women at 38 weeks gestation using 150 mg 3TC twice daily with zidovudine, and 10 women at 38 weeks gestation using 3TC 300 mg twice daily without other antiretrovirals. These trials were not designed or powered to provide efficacy information. 3TC pharmacokinetics in pregnant women were similar to those seen in non-pregnant adults and in postpartum women.

3TC concentrations were generally similar in maternal, neonatal, and umbilical cord serum samples. In a subset of subjects, amniotic fluid specimens were collected following natural rupture of membranes and confirmed that lamivudine crosses the placenta in humans. Amniotic fluid concentrations of lamivudine were typically 2 times greater than maternal serum levels and ranged from 1.2 to 2.5 mcg per mL (150 mg twice daily) and 2.1 to 5.2 mcg per mL (300 mg twice daily). Animal Data Lamivudine Studies in pregnant rats showed that 3TC is transferred to the fetus through the…