Zidovudine

CLINICAL USE

Nucleoside reverse transcriptase inhibitor: Treatment of HIV in combination with other antiretroviral drugs Prevention of maternal-foetal HIV transmission

DOSE IN NORMAL RENAL FUNCTION

Oral: 500–600 mg daily in 2–3 divided doses IV: 1–2 mg/kg every 4 hours

PHARMACOKINETICS

Molecular weight : 267.2

%Protein binding : 34–38

%Excreted unchanged in urine : 8–25

Volume of distribution (L/kg) : 1.6

half-life – normal/ESRD (hrs) : 1.1/1. 4–3

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Give 100% of normal dose every 8 hours

10 to 20 : Give 100% of normal dose every 8 hours

<10 : Give 50% of normal dose every 8 hours1

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD : Not dialysed. Dose as in GFR <10 mL/min

HD : Not dialysed. Dose as in GFR <10 mL/min Give post dialysis

HDF/high flux : Unknown dialysability. Dose as in GFR <10 mL/min Give post dialysis

CAV/VVHD : Not dialysed. Dose as in GFR 10 to 20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Antibacterials: absorption reduced by clarithromycin; avoid concomitant use with rifampicin

Anti-epileptics: phenytoin levels may be raised or lowered; concentration possibly increased by valproate (increased risk of toxicity)

Antifungals: concentration increased by fluconazole

Antivirals: profound myelosuppression with ganciclovir – avoid if possible; extreme lethargy on administration of IV aciclovir; effects of stavudine inhibited – avoid concomitant use; concentration reduced by tipranavir

ADMINISTRATION

Reconstition

Route

IV, oral

Rate of Administration

1 hour

Comments

Dilute with glucose 5% infusion to give a final concentration of 2 mg/mL or 4 mg/mL

OTHER INFORMATION

Dialysis has little effect on zidovudine, presumably because of rapid metabolism. The glucuronide metabolite (T½ =1 hour) has no antiviral activity and will be significantly removed by dialysis Patients with severe renal failure have 50% higher maximum plasma concentrations 90% of a dose is excreted renally, mostly as the glucuronide. There is substantial accumulation of this metabolite in renal failure Main risk in renal impairment is haematological toxicity

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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