An often unforgotten drug that we must be aware of
in ESRD patients is acyclovir.
Acyclovir can accumulate in ESRD if not dosed
appropriately and can lead to neurotoxicities- leading to confusion, tremors
and coma.
Initial
study of 7 patients
with end stage kidney disease receiving hemodialysis looked at levels following
hemodialysis with each patient received a single 800-mg tablet of acyclovir.
Plasma acyclovir levels were monitored over the next 48 h as well as before and
after the next routine dialysis. Peak plasma levels were achieved at 3 h (12.54
+/- 1.76 microM, range 8.5-17.5 microM) with the half-life calculated to be
20.2 +/- 4.6 h. Mean plasma level of 6.29 +/- 0.94 microM were within the
quoted range to inhibit herpes zoster virus (4-8 microM) at 18 h. Hemodialysis
(4-5 h) eliminated 51 +/- 11.5% of the acyclovir which remained at 48 h.
Computer modelling of various dose modifications suggests that a loading dose
of 400 mg and a maintenance dose of 200 mg twice daily is sufficient to
maintain a mean plasma acyclovir level of 6.4 +/- 0.8 microM. A further loading
dose (400 mg) after dialysis would raise the residual acyclovir concentration
by 6.1 +/- 1.0 microM.
Acute
acyclovir neurotoxicity can be treated in CKD and ESRD patients with dialysis.
The drug is water soluble, not albumin bound and small- hence an ideal dialysis
candidate for removal. It is important to
keep this toxicity in mind as many might come in to your office with non renal
dosing of this agent on ESRD and CKD patients and can lead to neurotoxicity. PD
is not an option; HD is preferred mode for removal of acyclovir.
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