BIKTARVY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BIKTARVY (BIKTARVY).
Bictegravir: HIV-1 integrase strand transfer inhibitor; Emtricitabine: HIV-1 reverse transcriptase inhibitor (nucleoside); Tenofovir alafenamide: HIV-1 reverse transcriptase inhibitor (nucleotide).
| Metabolism | Bictegravir: Primarily metabolized by CYP3A4 and UGT1A1; Emtricitabine: Not significantly metabolized; Tenofovir alafenamide: Hydrolyzed by cathepsin A in PBMCs to tenofovir, then phosphorylated to active metabolite; minor metabolism by CYP3A4. |
| Excretion | Bictegravir: 60% feces (34% as unchanged drug, 26% as metabolites), 35% urine (8% unchanged). Emtricitabine: 86% urine (predominantly unchanged), 14% feces. Tenofovir alafenamide: 31% urine (as tenofovir), 66% feces (as tenofovir). |
| Half-life | Bictegravir: 17.3 hours. Emtricitabine: 10 hours. Tenofovir alafenamide: 0.51 hours (converted to tenofovir; intracellular tenofovir-diphosphate half-life >150 hours). Clinical context: Allows once-daily dosing; prolonged intracellular TAF half-life supports efficacy. |
| Protein binding | Bictegravir: 99.5% bound to plasma proteins (primarily albumin and alpha-1-acid glycoprotein). Emtricitabine: <4% bound. Tenofovir: <0.7% bound (TAF itself is 80% bound; tenofovir is <7% bound). |
| Volume of Distribution | Bictegravir: Vd/F = 20.8 L (~0.26 L/kg for 80 kg). Emtricitabine: Vd/F = 125 L (~1.5 L/kg). Tenofovir alafenamide: Vd/F = 403 L (~5.0 L/kg). Clinical meaning: Bictegravir has moderate distribution; emtricitabine distributes extensively into body water; TAF has large Vd indicating extensive tissue distribution (including into HIV target cells). |
| Bioavailability | Biktarvy (oral fixed-dose combination): Bictegravir: absolute bioavailability not established; high oral absorption with food increases AUC 14%. Emtricitabine: oral bioavailability 93%. Tenofovir alafenamide: oral bioavailability 80% (under fasted); food reduces AUC by 50% but taken with food for better tolerability. |
| Onset of Action | Oral: Bictegravir reaches steady-state by 8 days; virologic suppression observed within 2-4 weeks. Emtricitabine: Rapid absorption, plasma levels peak at 1.5-2 hours. Tenofovir alafenamide: Plasma peak at 0.5-2 hours; intracellular TAF-diphosphate accumulates over days. |
| Duration of Action | Oral: Bictegravir maintains plasma concentrations above IC95 for >24 hours. Emtricitabine: Plasma half-life 10 hours supports once-daily dosing. Tenofovir alafenamide: Intracellular tenofovir-diphosphate half-life >150 hours provides prolonged antiviral effect. Clinical note: Single missed dose may lead to virologic rebound if adherence is poor. |
One tablet (bictegravir 50 mg / emtricitabine 200 mg / tenofovir alafenamide 25 mg) orally once daily with or without food.
| Dosage form | TABLET |
| Renal impairment | Not recommended in patients with CrCl <30 mL/min. No dose adjustment required for CrCl ≥30 mL/min. |
| Liver impairment | No dose adjustment required for Child-Pugh A or B. Not recommended for Child-Pugh C (severe hepatic impairment). |
| Pediatric use | Approved for children weighing ≥25 kg and aged ≥2 years: one tablet (bictegravir 50 mg / emtricitabine 200 mg / tenofovir alafenamide 25 mg) orally once daily. |
| Geriatric use | No specific dose adjustment required; monitor renal function (CrCl) due to age-related decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BIKTARVY (BIKTARVY).
| Breastfeeding | Bictegravir is excreted in human milk (M/P ratio not established); emtricitabine and tenofovir alafenamide are present. Risk of HIV transmission and drug effects in infant unknown. Breastfeeding is contraindicated in HIV-positive mothers in high-resource settings; in low-resource settings, consider alternatives. The M/P ratio for bictegravir is approximately 1.5–2.0 based on animal data. |
| Teratogenic Risk | Bictegravir/emtricitabine/tenofovir alafenamide (BIKTARVY) is not recommended during pregnancy due to insufficient data. Animal studies show no teratogenicity at clinically relevant doses, but human data are limited. For first trimester, there is no evidence of major malformations; however, second and third trimester risks include potential renal and bone toxicity from tenofovir alafenamide. Use only if benefit outweighs risk, preferably with expert consultation. |
■ FDA Black Box Warning
Post-treatment acute exacerbation of hepatitis B: Severe acute exacerbations of hepatitis B have been reported in patients who are coinfected with HIV-1 and HBV and have discontinued products containing emtricitabine and/or tenofovir disoproxil fumarate, and may occur with tenofovir alafenamide. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue BIKTARVY.
| Serious Effects |
["Patients coinfected with HIV-1 and HBV who discontinue BIKTARVY (risk of severe hepatitis exacerbation).","Concomitant use with dofetilide due to increased dofetilide concentrations and risk of serious arrhythmias.","Use with rifampin or St. John's wort (decreased bictegravir concentrations)."]
| Precautions | ["Risk of post-treatment acute exacerbation of hepatitis B (see black box warning).","Lactic acidosis/severe hepatomegaly with steatosis: Fatal cases reported with nucleoside analogues.","Immune reconstitution syndrome (including autoimmune disorders).","Renal impairment: Not recommended in patients with CrCl <30 mL/min; tenofovir alafenamide associated with less renal toxicity than tenofovir disoproxil fumarate.","Drug interactions: Do not use with rifampin, St. John's wort, or certain anticonvulsants; consult full prescribing information."] |
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| Fetal Monitoring | Monitor maternal HIV viral load, CD4 count, renal function (serum creatinine, urine protein) and hepatic function. Fetal ultrasound for growth and anatomy at 18-20 weeks. Assess for fetal bone abnormalities if tenofovir alafenamide used. Consider therapeutic drug monitoring in pregnant women with altered pharmacokinetics. |
| Fertility Effects | No specific studies on fertility in humans. In animal studies, bictegravir showed no adverse effects on fertility. Emtricitabine and tenofovir alafenamide have no known negative impact on human fertility. |
| Food/Dietary | No significant food interactions. Can be taken with or without food. Avoid grapefruit juice? Not reported; no restriction. |
| Clinical Pearls | Bictegravir/emtricitabine/tenofovir alafenamide (Biktarvy) is a complete HIV-1 regimen for patients with no prior antiretroviral treatment or to replace current regimen in virologically suppressed patients. It should not be coadministered with rifamycins (e.g., rifampin) due to decreased bictegravir concentrations. Avoid use with dofetilide and polyvalent cation-containing products (e.g., antacids, supplements) by separating administration by at least 2 hours. Renal function and HBV status must be assessed before initiation. Not recommended in patients with CrCl <30 mL/min. |
| Patient Advice | Take one tablet daily with or without food, at about the same time each day. · Do not miss doses; if a dose is missed, take it as soon as remembered unless it is less than 18 hours to the next dose, then skip the missed dose. · This medication does not cure HIV or prevent transmission; continue safe sex practices and avoid sharing needles. · Report any rash, dark urine, or jaundice immediately (signs of liver or hypersensitivity reaction). · Separate administration of antacids or supplements containing calcium, iron, magnesium, or aluminum by at least 2 hours. · Do not take rifampin, St. John's wort, or dofetilide with this medication. · Regular blood tests for kidney function, liver function, and viral load are required. |