Acyclovir
Acyclovir. Acyclic guanosine analog. Phosphorylated by viral thymidine kinase (HSV / VZV) → tri-phosphate is a competitive substrate +… Oral half-life 2.5 h.
Acyclic guanosine analog. Phosphorylated by viral thymidine kinase (HSV / VZV) → tri-phosphate is a competitive substrate + chain-terminator for viral DNA polymerase. Selectively activated in infected cells. Renal-cleared; nephrotoxicity at high IV doses if hydration is poor.
PK: the old citation was an HPLC ASSAY-VALIDATION study that dosed capsules only, so it supported nothing and the intravenous row had no arm behind it. Its ka 0.9 /h is the MEAN of the two Tmax values it does state, 0.8 and 1.0 hours. Re-sourced wholesale to de Miranda 1983 (PMID:6355048), which has both routes: verbatim "For patients with normal renal function (creatinine clearance (Clcr) greater than 80 ml/min/1.73m2) mean T1/2 beta and Cltot were 2.5 h and 327 ml/min/1.73 m2" and "the bioavailability of acyclovir was approximately 20%". THE HALF-LIFE IS VALID ONLY AT NORMAL RENAL FUNCTION — the same abstract states it is significantly renal-function dependent. V 70.7 L is DERIVED, not quoted: it is that paper own clearance and half-life combined, and is flagged as such. No abstract anywhere states an adult human acyclovir volume, and the stored 50 L was a shared default.
Pharmacokinetics
- Oral — t½ 2.5 h · F 20% · Vd 70.7 L
- IV — t½ 2.5 h · F 100% · Vd 70.7 L
Sources: PMID:18540483, PMID:6355048