A fixed-dose combination (FDC) tablet of three antiretroviral agents for the treatment of Human Immunodeficiency Virus type 1 (HIV-1) infection. It is a complete once-daily regimen containing two nucleoside reverse transcriptase inhibitors (NRTIs) - Lamivudine and Tenofovir disoproxil fumarate (TDF) - and one non-nucleoside reverse transcriptase inhibitor (NNRTI) - Efavirenz. This combination is a cornerstone of first-line antiretroviral therapy (ART) in India, recommended by the National AIDS Control Organization (NACO) guidelines for its efficacy, tolerability, and convenience.
Adult: One tablet (Lamivudine 300mg + TDF 300mg + Efavirenz 600mg) orally once daily.
Note: Take on an empty stomach, preferably at bedtime to improve tolerability of Efavirenz-related CNS effects (dizziness, drowsiness). Swallow whole with water. Taking Efavirenz with a high-fat meal increases absorption but may worsen side effects; consistency in timing relative to food is advised.
This combination inhibits the reverse transcriptase enzyme of HIV-1 via two distinct mechanisms, preventing the conversion of viral RNA into DNA and thus halting viral replication. Lamivudine and Tenofovir are nucleo(s/t)ide analogues that act as competitive substrates, causing chain termination. Efavirenz binds allosterically to a hydrophobic pocket near the enzyme's active site, inducing a conformational change that inhibits its function.
Pregnancy: Pregnancy Category D (as per US FDA). Efavirenz is contraindicated in the first trimester due to risk of neural tube defects (animal data and case reports). For women of childbearing potential, a pregnancy test is recommended before initiation and reliable contraception must be used. If pregnancy is confirmed in the first trimester, switching to an alternative regimen is recommended. Use in second/third trimester may be considered if benefits outweigh risks.
Driving: Patients should be advised that Efavirenz can cause dizziness, impaired concentration, and drowsiness, especially during the first weeks of therapy. They should avoid driving or operating machinery if they experience these symptoms.
| Rifampicin | Decreases Efavirenz plasma levels; may require Efavirenz dose increase to 800mg (not possible with this FDC). Alternative regimen preferred. | Major |
| Voriconazole | Efavirenz decreases Voriconazole levels; Voriconazole increases Efavirenz levels. Coadministration is contraindicated. | Major |
| Clarithromycin | Efavirenz decreases Clarithromycin levels while increasing its inactive metabolite. Consider alternative (e.g., Azithromycin). | Moderate |
| Warfarin | Efavirenz may induce metabolism, potentially decreasing Warfarin efficacy. Monitor INR closely. | Moderate |
| Anticonvulsants (Carbamazepine, Phenobarbital, Phenytoin) | May decrease Efavirenz levels; Efavirenz may alter anticonvulsant levels. Use with caution and monitor. | Moderate |
| Azole Antifungals (Ketoconazole, Itraconazole) | Efavirenz may decrease azole levels. Monitor efficacy. | Moderate |
| Artemether/Lumefantrine | Efavirenz may decrease Lumefantrine levels, potentially reducing antimalarial efficacy. | Moderate |
| Other Nephrotoxic drugs (Aminoglycosides, NSAIDs, IV Pentamidine) | Increased risk of renal toxicity with TDF. Monitor renal function. | Moderate |
| Didanosine (ddI) | Increased risk of ddI-related adverse effects and virologic failure; not recommended. | Major |
| Methadone | Efavirenz may decrease Methadone levels, potentially precipitating opioid withdrawal. Monitor and adjust methadone dose. | Moderate |
Same composition (Lamivudine (300mg) + Tenofovir disoproxil fumarate (300mg) + Efavirenz (600mg)), different brands: