Emtricitabine
Emtricitabine. NRTI — cytidine analog phosphorylated to FTC-TP, a chain-terminator for HIV-1 reverse transcriptase. Always combined with… Oral half-life 6.4 h.
NRTI — cytidine analog phosphorylated to FTC-TP, a chain-terminator for HIV-1 reverse transcriptase. Always combined with tenofovir as the dual NRTI backbone of HIV ART. Active against HBV. Excellent tolerability.
PK: CLASS 12 AT 2.55x, MEASURED AGAINST ITS OWN CITATION. That bioequivalence paper states none of the four stored values but does state the exposure that convicts them — "the AUC(0-infinity) were 10,615.14 ... ng x h/mL" at 200 mg, i.e. a clearance of 18.8 L/h against the stored 7.38 — and an independent study agrees at "apparent clearance (CL/F): 25.0 ... vs. 20.6 ... L/h". THE STORED HALF-LIFE IS NEITHER OF THIS DRUG TWO PHASES: "for emtricitabine, 41 h [36 to 54 h] versus 6.4 h (5.9 to 7.6 h)" over 216 h and over 0-24 h respectively, and for a once-daily model the 0-24 h figure is the right one. ka 1.4 implied a 2.26 h peak against a measured 1.05 h for the drug given alone — AND NOTE THAT 1.40 IS ANOTHER ARM Tmax IN HOURS IN THE SAME SENTENCE, which is the confirmed collision shape, though 1.4 L/kg is also this drug label volume so the path is not proven. V 99 L IS VERBATIM LAMIVUDINE INTRAVENOUS Vdss, and lamivudine holds 91 L, its own label figure — RECORDED, NOT ASSERTED, because the label coincidence is real and both volumes are wrong by the same mechanism anyway. THE FIX PRESERVES EXPOSURE AND COSTS THE PEAK: this drug is genuinely biexponential, and the AUC-matched volume under-predicts the observed peak by about half.
Pharmacokinetics
- Oral — t½ 6.4 h · F 93% · ka 3.4 h⁻¹ · Vd 177 L
Sources: PMID:27049055, PMID:26195515, PMID:22129166, PMID:24802019