Zidovudine

Zidovudine is used for: Cancer therapy-induced hyperuricaemia, HIV infection

HIV Infection 300 mg PO q12hr OR 200 mg PO q8hr (600 mg/day) IV: 1 mg/kg/dose 5-6x/day Maternal Dosing to Prevent Fetal HIV Transmission FDA-approved regimen 100 mg PO 5x/day until start of labor, in combination with other ART agents During labor and delivery: 2 mg/kg IV over 1 hr, THEN 1 mg/kg/hr IV continuous infusion until umbilical cord clamping NIH perinatal guidelines Indicated during labor and delivery for women who have received antepartum ART and their HIV RNA levels are >400 copies/mL, or in women who have not received antepartum ART 2 mg/kg IV loading dose infused over 1 hr, THEN 1 mg/kg/hr until umbilical cord clamping Women who have received antepartum ART and their HIV RNA levels are <400 copies/mL do not require IV zidovudine Hepatic Impairment Reduction in daily dose or extension of dosing interval may be necessary

HIV Infection, Treatment 4 weeks-18 years 240 mg/m² PO q12hr or 160 mg/m² PO q8hr, OR use mg/kg dosing 4 to <9 kg: 12 mg/kg PO q12hr or 8 mg/kg PO TID > 9 to <30 kg: 9 mg/kg PO q12hr or 6 mg/kg PO TID >30 kg: 300 mg PO q12hr or 200 mg PO TID IV intermittent infusion: 120 mg/m² IV q6h IV continuous infusion: 20 mg/m²/hr IV HIV Perinatal Transmission Prevention Indicated to prevent mother-to-child HIV transmission in all HIV-exposed infants FDA approved regimen 2 mg/kg PO q6hr or 1.5 mg/kg IV q6hr NIH perinatal guidelines <30 weeks’ gestation: 2 mg/kg PO or 1.5 mg/kg IV BID; after age 4 weeks, advance to 3 mg/kg PO or 2.3 mg/kg IV q12hr >30 to <35 weeks’ gestation: 2 mg/kg PO BID; after age 15 days, advance to 3 mg/kg PO or 2.3 mg/kg IV q12hr >35 weeks’ gestation: 4 mg/kg PO or 3 mg/kg IV BID x6 weeks

Renal Impairment CrCl < 15 mL/min (maintained on hemodialysis or peritoneal dialysis): 100 mg PO or 1 mg/kg IV q6-8 hr; alternatively 100 mg PO qDay or 300 mg/day PO

May be taken with or without food. IV Preparation Dilute to not to exceed 4 mg/mL w/ D5W IV Administration Infuse over 1 hr

Hypersensitivity; abnormally low neutrophil counts (<0.75 x 109/L) or Hb levels (<7.5 g/dL or 4.65 mmol/L); newborn infants w/ hyperbilirubinaemia requiring treatment other than phototherapy, or w/ increased transaminase levels >5 times the ULN. Lactation. Concomitant use w/ interferon alfa (w/ or w/o ribavirin) in HIV and hepatitis B or C virus co-infected patients.

Severe renal and hepatic impairment. Childn. Pregnancy. Monitoring Parameters Monitor viral load, CD4 count; CBC w/ differential, LFT, lipid, glucose. Observe for appearance of opportunistic infection.

Pregnancy Available data from the APR show no difference in the overall risk of birth defects for lamivudine or zidovudine compared with background rate for birth defects of 2.7% in the Metropolitan Atlanta Congenital Defects Program (MACDP) reference population; APR uses the MACDP as the U.S. reference population for birth defects in the general population; MACDP evaluates women and infants from a limited geographic area and does not include outcomes for births that occurred at less than 20 weeks gestation; rate of miscarriage is not reported in the APR Hyperlactatemia, which may be due to mitochondrial dysfunction, reported in infants with in utero exposure to zidovudine-containing products; events were transient and asymptomatic in most cases; developmental delay, seizures, and other neurological disease also reported; a causal relationship between these events and exposure to zidovudine-containing products in utero or peri-partum not established Drug has been shown to cross placenta and concentrations in neonatal plasma at birth were essentially equal to those in maternal plasma at delivery; mild, transient elevations in serum lactate levels reported, which may be due to mitochondrial dysfunction, in neonates and infants exposed in utero or peri-partum to zidovudine-containing products; clinical relevance of transient elevations in serum lactate is unknown Lactation The Centers for Disease Control and Prevention recommend that HIV-1-infected mothers in the United States not breastfeed infants to avoid risking postnatal transmission of HIV-1 infection; lamivudine is present in human milk; there is no information on effects of lamivudine or zidovudine on breastfed infant or effects of drugs on milk production; because of potential for (1) HIV-1 transmission (in HIV-negative infants), (2)developing viral resistance (in HIV-positive infants), and (3) serious adverse reactions in a breastfed infant, instruct mothers not to breastfeed if they are receiving therapy

Decreased zidovudine concentration with tipranavir. Increased risk of peripheral neuropathy with bortezomib. Increased haematological toxicity with IV pentamidine, lamivudine, dapsone, vancomycin flucytosine, amphotericin, ganciclovir, interferon alfa, cyclophosphamide and other bone marrow suppressive or cytotoxic agents Increased risk of zidovudine toxicity with atovaquone, chloramphenicol, fluconazole, valproate. Decreased absorption with clarithromycin, minimise interactions by admin at least 2 hours apart. Increased zidovudine concentration and increased potential for hypersensitivity reactions with probenecid. Increased zidovudine clearance and haematological toxicity with rifampicin. Increased bioavailability of zidovudine with nimodipine. Increased incidences of headache with benzodiazepines. Possible increase in zidovudine concentration with methadone. Potentially Fatal: Avoid stavudine (due to inhibition of activation of stavudine), didanosine, ribavirin (antagonize effect of zidovudine), zalcitabine (inferior virological activity and a higher rate of side effects) with zidovudine. Increased risk of toxicity (e.g. hepatic decompensation, neutropenia) in patients with interferon alfa with or without ribavirin.

Side effects of Zidovudine : >10% Anemia (23% in children), Anorexia (11%), Diarrhea (17%), Fever (16%), Granulocytopenia (39% in children), Headache, severe (42%), Leukopenia (39%), Nausea (46-61%), Pain (20%), Rash (17%), Vomiting (6-25%), Weakness (19%) 1-10% Malaise (8%), Dizziness (6%), Insomnia (5%), Somnolence (8%), Hyperpigmentation of nails (bluish-brown), Dyspepsia (5%), Changes in platelet count, Paresthesia (6%) Potentially Fatal: Lactic acidosis, severe hepatomegaly with steatosis, hepatotoxicity. Blood dyscrasias, e.g. serious anaemia (may require transfusion), neutropenia, leucopenia.

Zidovudine is a thymidine analogue. It is phosphorylated in the body to its active form zidovudine triphosphate which interferes in DNA synthesis of retroviruses by inhibiting DNA replication. Zidovudine inhibits the key enzyme reverse transcriptase. Human DNA polymerase is inhibited only at a conc 100 times more than that required to inhibit viral reverse transcriptase.