DESCOVY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DESCOVY (DESCOVY).
DESCOVY is a fixed-dose combination of emtricitabine and tenofovir alafenamide. Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) that inhibits HIV-1 reverse transcriptase by competing with the natural substrate deoxycytidine-5'-triphosphate and incorporating into viral DNA, causing chain termination. Tenofovir alafenamide is a prodrug of tenofovir, which is also an NRTI; it is taken up by cells and converted to tenofovir diphosphate, which inhibits HIV-1 reverse transcriptase via chain termination after incorporation into viral DNA.
| Metabolism | Emtricitabine is not significantly metabolized; it is primarily excreted renally. Tenofovir alafenamide is metabolized primarily by cathepsin A in peripheral blood mononuclear cells and by CYP3A4 in hepatocytes; it is also a substrate of P-glycoprotein (P-gp) and BCRP. |
| Excretion | Tenofovir alafenamide (TAF): 80% excreted renally as unchanged drug via glomerular filtration and active tubular secretion; 15% recovered in feces. Emtricitabine (FTC): 70% excreted renally as unchanged drug via glomerular filtration and active tubular secretion; 14% as metabolites; remainder in feces. |
| Half-life | TAF: 0.51 hours (intracellular tenofovir diphosphate ~150 hours). FTC: 10 hours (intracellular triphosphate >39 hours). Clinical context: Long intracellular half-life supports once-daily dosing. |
| Protein binding | TAF: ~80% bound to plasma proteins (primarily albumin). FTC: <4% bound to plasma proteins. |
| Volume of Distribution | TAF: 1.31 L/kg (steady-state). FTC: 1.4 L/kg (steady-state). Clinical meaning: Distribution extensively into total body water, with penetration into tissues including gastrointestinal mucosa and genital tract. |
| Bioavailability | TAF: 25-31% (oral, under fasting conditions); enhanced with moderate-fat meal (35-45%). FTC: 93% (oral). |
| Onset of Action | Oral: TAF and FTC are prodrugs; intracellular conversion leads to antiviral activity within hours. Clinical effect (HIV-1 RNA reduction) typically observed within 2-4 weeks. |
| Duration of Action | Oral: Dosing interval 24 hours due to once-daily regimen; intracellular tenofovir diphosphate and emtricitabine triphosphate concentrations support HIV-1 suppression over 24 hours. |
One tablet (emtricitabine 200 mg / tenofovir alafenamide 25 mg) orally once daily with or without food.
| Dosage form | TABLET |
| Renal impairment | Not recommended in patients with estimated creatinine clearance (CrCl) < 30 mL/min. No dose adjustment required for CrCl ≥ 30 mL/min. |
| Liver impairment | Not recommended in patients with severe hepatic impairment (Child-Pugh class C). No dose adjustment required for mild or moderate (Child-Pugh class A or B) hepatic impairment. |
| Pediatric use | Approved for adolescents weighing ≥ 35 kg: one tablet (200/25 mg) once daily. For patients weighing < 35 kg, other formulations are available. |
| Geriatric use | No specific dose adjustment required; select based on renal function. Monitor for renal adverse effects due to age-related renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DESCOVY (DESCOVY).
| Breastfeeding | Maternal use of Descovy is generally considered compatible with breastfeeding; however, caution is advised. Emtricitabine is excreted in human milk; tenofovir alafenamide is likely excreted as well. The M/P ratio for emtricitabine is approximately 1.6. No data on tenofovir alafenamide. Benefits of breastfeeding should be weighed against potential risks. |
| Teratogenic Risk | Descovy (emtricitabine/tenofovir alafenamide) is classified as Pregnancy Category B. There are no adequate and well-controlled studies in pregnant women. Animal studies have not shown evidence of teratogenicity, but fetal harm cannot be ruled out. Use during pregnancy only if clearly needed. The Antiretroviral Pregnancy Registry monitors outcomes. |
■ FDA Black Box Warning
WARNING: POST-TREATMENT ACUTE EXACERBATION OF HEPATITIS B: Severe acute exacerbations of hepatitis B (HBV) have been reported in patients co-infected with HIV-1 and HBV who have discontinued DESCOVY. Hepatic function should be monitored closely in these patients.
| Serious Effects |
["Patients with unknown or positive HIV-1 status (for PrEP indication)","Patients with creatinine clearance <30 mL/min (for treatment indication; note: PrEP is not recommended if CrCl <30 mL/min, but not listed as absolute contraindication in labeling)"]
| Precautions | ["New onset or worsening renal impairment: Cases of acute renal failure, Fanconi syndrome, and renal tubular injury have been reported. Monitor serum creatinine and urine glucose before and during therapy.","Lactic acidosis and severe hepatomegaly with steatosis: Reported with nucleoside analogs, including tenofovir. Discontinue if clinical or laboratory findings suggestive of lactic acidosis or hepatotoxicity occur.","Decreases in bone mineral density (BMD): Observed with tenofovir-containing regimens. Consider monitoring BMD in patients with a history of pathologic fracture or other risk factors for osteoporosis.","Immune reconstitution syndrome: May occur during initial treatment, including autoimmune disorders with variable time to onset.","Risk of HIV-1 resistance: DESCOVY alone should not be used for treatment of HIV-1; it is only indicated for PrEP in HIV-1-negative individuals. Unrecognized HIV-1 infection should be excluded before starting PrEP."] |
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| Fetal Monitoring | Monitor liver function tests and renal function (serum creatinine, estimated glomerular filtration rate) at baseline and periodically during pregnancy. Monitor HIV viral load and CD4 count regularly. Assess for signs of lactic acidosis and hepatotoxicity. Fetal ultrasound may be considered per standard prenatal care. |
| Fertility Effects | No human data on fertility impairment. Animal studies show no adverse effects on mating or fertility at clinically relevant doses. Descovy is not expected to impair fertility in humans based on available evidence. |