Zidovudine

RETROVIR

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Pronunciation: zye-DOE-vyoo-deen

Zidovudine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Zidovudine ballicule

What it isZidovudine (AZT) is a nucleoside reverse transcriptase inhibitor (NRTI) that, once phosphorylated, inhibits HIV reverse transcriptase and terminates viral DNA chain elongation.

Why this oneA cornerstone of early combination antiretroviral therapy, it is still used within regimens and notably for prevention of mother-to-child HIV transmission.

What limits itIt carries a boxed warning for hematologic toxicity, symptomatic myopathy, and lactic acidosis with severe hepatomegaly.

Zidovudine molecular structure (skeletal formula) — Molecular structure: Zidovudine

FDA label

Read the full label on DailyMed ↗

BOXED WARNING Hematologic toxicity (neutropenia, severe anemia — especially advanced HIV-1 disease); symptomatic myopathy with prolonged use; lactic acidosis and severe hepatomegaly with steatosis, including fatal cases — suspend treatment if findings suggest lactic acidosis or pronounced hepatotoxicity.

FDA dosing	Population	Start	Target	Max
HIV-1 infection (in combination with other antiretrovirals)	Adults	300 mg BID	300 mg BID	300 mg BID
HIV-1 infection	Peds 4 wk to <18 y, 4 to <9 kg	12 mg/kg BID or 8 mg/kg TID	24 mg/kg/day	Do not exceed adult dose
HIV-1 infection	Peds >=9 to <30 kg	9 mg/kg BID or 6 mg/kg TID	18 mg/kg/day	Do not exceed adult dose
HIV-1 infection	Peds >=30 kg	300 mg BID or 200 mg TID	600 mg/day	600 mg/day
Prevention of maternal-fetal HIV-1 transmission — maternal	Pregnant women >14 wk gestation	100 mg PO 5x/day until labor; then IV 2 mg/kg over 1 h, then 1 mg/kg/h until cord clamping	Through delivery	100 mg 5x/day PO
Prevention of maternal-fetal HIV-1 transmission — neonatal	Neonates (start within 12 h of birth, through 6 wk of age)	2 mg/kg PO q6h (8 mg/kg/day); IV if unable to take oral: 1.5 mg/kg over 30 min q6h	Continue through 6 weeks of age	8 mg/kg/day PO

Renal CrCl <15 mL/min or hemodialysis/peritoneal dialysis: 100 mg q6-8h

Hepatic Insufficient data to recommend dose adjustment; concentrations increased in hepatic impairment — monitor hematologic toxicities frequently

Instructions

Alternative pediatric dosing by BSA: 480 mg/m2/day divided (240 mg/m2 BID or 160 mg/m2 TID)
Assess children for ability to swallow tablets; use syrup if not, and for accurate neonatal dosing (0.1-mL graduated syringe)
Interrupt dosing for significant anemia (Hgb <7.5 g/dL or >25% drop) or neutropenia (granulocytes <750/mm3 or >50% drop) until marrow recovery; epoetin alfa may support resumption

Available strengths

cap 100 mg
tab 300 mg
sol 50 mg/5 mL
inj 10 mg/mL

Cautions

Use with caution if bone marrow compromise (granulocytes <1,000/mm3 or Hgb <9.5 g/dL); frequent blood counts in advanced disease, periodic counts otherwise
Myopathy and myositis with prolonged use
Lactic acidosis/severe hepatomegaly with steatosis — suspend if suspected; female sex and obesity are risk factors
Avoid coadministration with ribavirin (exacerbation of anemia); hepatic decompensation (some fatal) in HIV/HCV co-infected patients on interferon alfa +/- ribavirin
Immune reconstitution syndrome
Lipoatrophy (face, limbs, buttocks) related to cumulative exposure; only partially reversible — assess regularly and consider switching

Adverse reactions

Headache (63%), malaise (53%), nausea (51%), anorexia (20%), vomiting (17%)
Anemia and neutropenia (most significant in advanced disease); pancytopenia (reversible in most)
Also >=5%: abdominal cramps/pain, arthralgia, chills, dyspepsia, fatigue, insomnia, musculoskeletal pain, myalgia, neuropathy
Postmarketing: aplastic anemia, pure red cell aplasia, cardiomyopathy, hepatitis, lactic acidosis, pancreatitis, rhabdomyolysis, seizures, Stevens-Johnson syndrome/TEN, skin and nail pigmentation, gynecomastia

Pregnancy APR registry (>13,000 exposures): no increase in overall birth defects vs 2.7% background; maternal-fetal HIV-1 transmission reduced 24.9% to 7.8% in ACTG trial; transient hyperlactatemia reported in exposed infants

Lactation Do not breastfeed (CDC: HIV-1-infected mothers should not breastfeed; zidovudine present in human milk; transmission, viral resistance, and infant adverse-reaction risks)

Cost

Zidovudine (RETROVIR)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $	CostPlus
300 mg	tab	60 BID	$27.83/mo	offered
100 mg	cap	60 BID		offered
50 mg/5 mL	sol	per unit		not offered
10 mg/mL	inj	per unit		not offered

Generic entry2005

⚠ BOXED WARNINGS

Hematologic toxicity (neutropenia/anemia)
Symptomatic myopathy
Lactic acidosis and severe hepatomegaly with steatosis

Principal riskBoxed warning: hematologic toxicity (neutropenia/anemia), symptomatic myopathy, and lactic acidosis with severe hepatomegaly.

Classes and tags

Clinical profile

Therapeutic safety burden2 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryUnknown / historical label unavailable

Defining liabilityAgent-specific renal, hepatic, hematologic, metabolic and drug-interaction toxicity.

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