Descovy
Descovy
Generic Name
Descovy
Brand Names
for the fixed‑dose combination of emtricitabine 200 mg and tenofovir alafenamide (TAF) 25 mg. It is approved by the FDA for HIV‑1 prevention in adults and adolescents ≥ 12 years, including use as oral pre‑exposure prophylaxis (PrEP) and for HIV treatment in combination regimens that do not contain a protease inhibitor.
Mechanism
- Emtricitabine is a nitro‑imidazole reverse‑transcriptase inhibitor (NRTI) that competes with deoxycytidine triphosphate for incorporation into viral DNA. Once incorporated, it causes chain termination.
- Tenofovir alafenamide (TAF) is a prodrug of tenofovir that releases the active tenofovir diphosphate directly inside target cells. It also acts as an NRTI, blocking the addition of nucleotides to the growing viral DNA chain.
- The combination provides dual blockade at the reverse‑transcription step, giving high potency against HIV‑1 with a low potential for resistance when used in appropriate regimens.
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Pharmacokinetics
| Parameter | Descovy (TAF/Emtricitabine) | Notes |
| Absorption | Oral; peak plasma emtricitabine ~0.5 h, TAF ~1–2 h. | Food slightly increases emtricitabine AUC. |
| Distribution | High protein binding > 95 %; volume of distribution ~10 L for emtricitabine, ~3–4 L for TAF. | Good penetration into genital tract; limited CNS distribution. |
| Metabolism | TAF is a stable prodrug; hydrolyzed by cathepsin A to tenofovir; negligible first‑pass metabolism. | Emtricitabine not metabolized. |
| Elimination | Renal excretion: 70 % emtricitabine unchanged, 30 % as metabolites; tenofovir excreted via kidneys after conversion. | Clearance unchanged in mild‑moderate hepatic impairment. |
| Half‑life | Emtricitabine ~10 h; tenofovir (from TAF) ~9 h. | Steady‑state achieved in 4–7 days. |
| Drug interactions | Minimal; modest impact of CYP2B6 inhibitors on TAF conversion. No clinically relevant interactions with antacids, calcium, or antiretrovirals (except boosting agents). | Consider renal‑dose adjustments if CrCl <60 mL/min. |
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Indications
- Pre‑exposure prophylaxis (PrEP) for adults and adolescents ≥ 12 years who are HIV‑negative but at substantial risk of acquisition (e.g., MSM, sex workers, serodiscordant couples).
- Treatment of HIV‑1 infection as part of a fully suppressive antiretroviral regimen that does not include a protease inhibitor.
- Pre‑conception and early pregnancy prophylaxis in high‑risk women when tenofovir disoproxil fumarate (TDF) is contraindicated.
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Dosing
| Indication | Dose | Administration | Notes |
| PrEP | 200 mg emtricitabine / 25 mg TAF once daily | Oral capsule, at the same time each day | If > 1 missed dose, begin delayed‑release or repeat PrEP regimen per CDC guidelines. |
| Treatment (non‑PI regimens) | 200 mg emtricitabine / 25 mg TAF once daily | Oral capsule, can be taken with or without food | Combine with two or more other ARVs per DHHS/IAS‑Worldwide guidelines. |
| Special Populations | Same as above | For patients ≥ 12 y, < 12 y only in research settings | Mother‑to‑child transmission: use only if TDF contraindicated; monitor infant. |
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Adverse Effects
- Common (≥ 5 %)
- Nausea, dysgeusia, diarrhea
- Headache, fatigue
- Mild transaminase elevation (≈ 2× ULN)
- Less Common (1–5 %)
- Anemia (rare)
- Insomnia, mood changes
- Serious (≤ 1 %)
- Acute kidney injury (elevated serum creatinine > 1.5× baseline)
- Ototoxicity (rare) – monitor Communication tests in susceptible patients
- Severe hypersensitivity reactions (SJS/TEN) – rarely reported but serious.
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Monitoring
| Parameter | Frequency | Rationale |
| Serum creatinine & eGFR | Baseline; 1 month after initiation; then every 3–6 months | Detect renal toxicity early. |
| Liver transaminases | Baseline; 1 month; then annually | Capture hepatic toxicity. |
| HIV viral load | Baseline; every 3 months during treatment | Ensure virologic suppression. |
| Bone mineral density (DEXA) | Baseline (if osteopenia risk); repeat 12–24 months | Monitor for TAF‑associated bone loss. |
| Drug resistance testing | If virologic failure | Guide future ARV selection. |
| Pregnancy testing | At baseline and every cycle for women of childbearing potential | Minimize fetal exposure. |
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Clinical Pearls
- TAF vs. TDF – TAF achieves higher intracellular tenofovir diphosphate concentrations while keeping plasma tenofovir low, substantially reducing renal and bone toxicity. Choose Descovy for patients with pre‑existing CKD or osteoporosis risk.
- PrEP Adherence – One missed dose 48 h requires a plan (e.g., start delayed‑release). Maintain daily dosing to achieve 95 % adherence for maximal efficacy.
- Drug interactions are minimal, but TAF dose adjustments are not needed for boosting agents (e.g., ritonavir) unlike TDF.
- For sexual transmission prevention, Descovy is equally effective across MSM, serodiscordant couples, and heterosexual men; its high drug levels in rectal tissues support use for receptive anal intercourse.
- Pregnancy – Use Descovy only if TDF contraindicated; transport into fetus is lower, but limited data exist; counsel patients accordingly and monitor maternal/fetal health.
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