Version May 2024
Zidovudine has been associated with hematologic toxicity, including neutropenia and severe anemia, particularly in patients with advanced HIV-1 disease.
Prolonged use of zidovudine has been associated with symptomatic myopathy.
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination, including with zidovudine and other antiretrovirals. Suspend treatment if clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity occur.
Note: Patients should receive IV therapy only until oral therapy can be administered.
Perinatal HIV-1 transmission, prevention: Recommendations for use of intrapartum zidovudine are based on maternal HIV RNA levels assessed at 36 weeks' gestation or within 4 weeks of delivery, and other factors. Intrapartum zidovudine IV is recommended when HIV RNA is >1,000 copies/mL or when the HIV RNA level is unknown near delivery. Intrapartum zidovudine IV should also be administered if a lack of adherence is suspected since the last RNA result or when HIV is initially diagnosed during labor. Patients with HIV RNA >1,000 copies/mL should be given zidovudine even in cases of documented zidovudine resistance unless there is a history of hypersensitivity. Intrapartum zidovudine IV is not needed in patients receiving antiretroviral therapy (ART) who have HIV RNA <50 copies/mL near delivery AND who are adherent to their ART regimen. If a fetal scalp electrode is needed during labor, consider the fetal risk of HIV transmission high even if maternal HIV RNA is <50 copies/mL. The decision to administer zidovudine IV intrapartum to patients with HIV RNA ≥50 and ≤1,000 copies/mL near delivery should be made on a case-by-case basis (Ref).
During labor and delivery:
IV : Loading dose: 2 mg/kg over 1 hour followed by a continuous IV infusion of 1 mg/kg/hour until delivery (ie, clamping of the umbilical cord). For scheduled cesarean delivery, begin IV zidovudine at least 3 hours before surgery to provide dosing for a minimum of 3 hours. In cases of an urgent, unscheduled cesarean delivery due to maternal and fetal indications, consider administering the loading dose then proceeding to delivery (Ref). Note: Dosage based on total body weight.
HIV-1 infection, treatment:
Oral: 300 mg twice daily, in combination with other antiretroviral agents.
IV: 1 mg/kg/dose every 4 hours around-the-clock (6 doses daily) in combination with other antiretroviral agents.
HIV-1 nonoccupational postexposure prophylaxis (nPEP) (off-label use):
Note: Not a component of the recommended antiretroviral regimen for patients with CrCl ≥60 mL/minute (Ref).
Oral: 300 mg twice daily in combination with other antiretroviral agents. Initiate therapy within 72 hours of exposure and continue for 28 days (Ref).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
CrCl ≥15 mL/minute: No dosage adjustment necessary.
CrCl <15 mL/minute:
Oral: 100 mg every 6 to 8 hours.
IV: 1 mg/kg every 6 to 8 hours.
End-stage renal disease on intermittent hemodialysis:
Oral: 100 mg every 6 to 8 hours.
IV: 1 mg/kg every 6 to 8 hours.
Peritoneal dialysis:
Oral: 100 mg every 6 to 8 hours.
IV: 1 mg/kg every 6 to 8 hours.
CRRT: No adjustment needed (Ref).
There are no specific dosage adjustments provided in the manufacturer's labeling (has not been studied). However, adjustment may be necessary due to extensive hepatic metabolism. Closely monitor patients for hematologic toxicities.
Consider dose interruption for significant anemia (hemoglobin <7.5 g/dL or >25% reduction from baseline) and/or neutropenia (granulocyte count <750 cells/mm3 or >50% reduction from baseline) until evidence of recovery. Resumption in dose in combination with adjunctive measures (eg, epoetin alfa) may be appropriate, depending on erythropoietin level and patient tolerance.
Refer to adult dosing.
(For additional information see "Zidovudine: Pediatric drug information")
HIV-1 infection, treatment: Use in combination with other antiretroviral (ARV) agents; evaluate gene mutation and ARV resistance patterns (refer to https://www.iasusa.org and https://hivdb.stanford.edu/ for more information). Although described in some international product labeling, IV zidovudine dosing is not recommended for treatment of HIV as other ARVs are only available as oral products, and administration of an incomplete regimen (zidovudine monotherapy) is not recommended. IV zidovudine dosing may still be utilized for prophylaxis in neonates or during labor/delivery; see "Dosing: Neonatal" or "Dosing: Adult" (Ref).
Infants (PMA ≥35 weeks, PNA ≥4 weeks, and weight ≥4 kg), Children, and Adolescents:
Weight-directed dosing:
4 to <9 kg: Oral: 12 mg/kg/dose twice daily.
9 to <30 kg: Oral: 9 mg/kg/dose twice daily.
≥30 kg: Oral: 300 mg twice daily.
BSA-directed dosing: Oral: 240 mg/m2/dose every 12 hours, range: 180 to 240 mg/m2/dose every 12 hours (maximum dose: 300 mg/dose).
HIV-1 nonoccupational postexposure prophylaxis (nPEP) (Ref): Note: Initiate therapy within 72 hours of exposure and continue for 28 days; use in combination with other antiretroviral agents.
Infants (PMA ≥35 weeks and PNA ≥4 weeks of age) and Children:
4 to <9 kg: Oral: 12 mg/kg/dose twice daily.
9 to <30 kg: Oral: 9 mg/kg/dose twice daily.
≥30 kg: Oral: 300 mg twice daily.
Adolescents: Oral: 300 mg twice daily.
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Dosing adjustment for hematologic toxicity: Consider interruption of therapy for significant anemia (Hgb <7.5 g/dL or >25% decrease from baseline) and/or significant neutropenia (ANC <750 cells/mm3 or >50% decrease from baseline) until evidence of bone marrow recovery occurs; once bone marrow recovers, dose may be resumed using appropriate adjunctive therapy (eg, epoetin alfa); for persistent, severe anemia thought to be due to zidovudine, consider zidovudine discontinuation and implementation of a new regimen (Ref).
Infants >6 weeks, Children, and Adolescents:
The following adjustments have been recommended (Ref): Note: Renally adjusted dose recommendations are based on oral doses of 160 mg/m2/dose every 8 hours and IV dose of 120 mg/m2/dose every 6 hours.
GFR ≥10 mL/minute/1.73 m2: No dosage adjustment required
GFR <10 mL/minute/1.73 m2: Administer 50% of dose every 8 hours
Intermittent hemodialysis (IHD): Administer 50% of dose every 8 hours
Peritoneal dialysis (PD): Administer 50% of dose every 8 hours
Continuous renal replacement therapy (CRRT): No adjustment required
There are no specific dosage adjustments provided in the manufacturer's labeling (has not been studied); however, dosage reduction may be necessary due to extensive hepatic metabolism. Use with caution; closely monitor for hematologic toxicities (Ref).
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Percentages noted with oral administration in adults unless otherwise indicated.
>10%:
Gastrointestinal: Anorexia (20%), nausea (51%), vomiting (17%)
Hematologic & oncologic: Anemia (neonates: 22%; adults: grades 3/4: 1%)
Nervous system: Headache (63%), malaise (53%)
1% to 10%:
Gastrointestinal: Abdominal cramps (≥5%), abdominal pain (≥5%), constipation (6%), dyspepsia (≥5%)
Nervous system: Asthenia (9%), chills (≥5%), fatigue (≥5%), insomnia (≥5%), neuropathy (≥5%)
Neuromuscular & skeletal: Arthralgia (≥5%), musculoskeletal pain (≥5%), myalgia (≥5%)
<1%: Hepatic: Hyperbilirubinemia
Frequency not defined:
Hematologic & oncologic: Neutropenia
Local: Injection-site reaction (IV, including irritation at injection site, pain at injection site)
Neuromuscular & skeletal: Lipoatrophy
Postmarketing (any population):
Cardiovascular: Cardiomyopathy, chest pain, orthostatic hypotension (Loke 1990), syncope, vasculitis
Dermatologic: Diaphoresis, dyschromia (including skin hyperpigmentation) (Premjith 2022), nail disease (changes in pigmentation including nail hyperpigmentation) (Chawre 2012, Premjith 2022), pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis (Murri 1996), urticaria
Endocrine & metabolic: Gynecomastia, increased lactate dehydrogenase, lactic acidosis (Mahto 2018), redistribution of body fat
Gastrointestinal: Dysgeusia, dysphagia, flatulence, oral mucosa hyperpigmentation, oral mucosa ulcer, pancreatitis (including acute pancreatitis) (Mahto 2018)
Genitourinary: Urinary frequency, urinary hesitancy
Hematologic & oncologic: Aplastic anemia, hemolytic anemia, leukopenia, lymphadenopathy, pancytopenia, pure red cell aplasia (Balakrishnan 2010)
Hepatic: Hepatitis, hepatomegaly with steatosis, jaundice
Hypersensitivity: Hypersensitivity reaction (including anaphylaxis, angioedema)
Immunologic: Immune reconstitution syndrome
Nervous system: Anxiety, confusion, decreased mental acuity, depression, dizziness, drowsiness, mania, pain, paresthesia, seizure, tremor, vertigo
Neuromuscular & skeletal: Arthropathy (Murphy 1994), back pain, increased creatine phosphokinase in blood specimen, lipotrophy, muscle spasm, myopathy (Mahto 2018), myositis, rhabdomyolysis
Ophthalmic: Amblyopia, macular edema, photophobia
Otic: Hearing loss
Respiratory: Dyspnea, flu-like symptoms, rhinitis, sinusitis
Potentially life-threatening hypersensitivity to zidovudine or any component of the formulation
Canadian labeling: Additional contraindications (not in US labeling): Neutrophil count <750/mm3 or hemoglobin <7.5 g/dL (4.65 mmol/L)
Concerns related to adverse effects:
• Hematologic toxicity: Hematologic toxicity, including neutropenia and severe anemia have been reported with use, especially with advanced HIV-1 disease. Toxicity may be related to duration of use and prior bone marrow reserve. Hemoglobin reduction may occur in as early as 2 to 4 weeks; neutropenia usually occurs after 6 to 8 weeks. Pancytopenia has been reported (usually reversible). Use with caution in patients with bone marrow compromise (granulocytes <1,000 cells/mm3 or hemoglobin <9.5 g/dL). Dose interruption may be required in patients who develop anemia or neutropenia.
• Immune reconstitution syndrome: Patients may develop immune reconstitution syndrome resulting in the occurrence of an inflammatory response to an indolent or residual opportunistic infection during initial HIV treatment or activation of autoimmune disorders (eg, Graves disease, polymyositis, Guillain-Barré syndrome) later in therapy; further evaluation and treatment may be required.
• Lipoatrophy: May cause loss of subcutaneous fat, especially in the face, limbs, and buttocks. Lipoatrophy incidence and severity are related to cumulative exposure and may be only partially reversible; improvement may take months to years after switching to a regimen that does not contain zidovudine. Monitor patients for signs of lipoatrophy and consider switching to a non-zidovudine-containing regimen if lipoatrophy occurs.
Disease-related concerns:
• Hepatic impairment: Hematologic toxicity may be increased due to increased serum concentrations in patients with hepatic impairment.
• Renal impairment: Use with caution in patients with CrCl <15 mL/minute; dosage adjustment recommended.
Dosage form specific issues:
• Benzyl alcohol and derivatives: Some dosage forms may contain sodium benzoate/benzoic acid; benzoic acid (benzoate) is a metabolite of benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC, 1982); some data suggests that benzoate displaces bilirubin from protein binding sites (Ahlfors 2001); avoid or use dosage forms containing benzyl alcohol derivative with caution in neonates. See manufacturer's labeling.
• Injection: Latex is used in vial stopper. May cause allergic reactions in latex-sensitive individuals.
Use with caution in patients with ANC <1,000 cells/mm3 or Hgb <9.5 g/dL; consider interruption of therapy for significant anemia (Hgb <7.5 g/dL or reduction >25% of baseline; neonates: Hgb <7 g/dL or symptomatic) or neutropenia (ANC <750 cells/mm3 or reduction >50% from baseline; neonates: ANC <500 cells/mm3) (HHS [pediatric] 2023; manufacturer's labeling). If significant anemia or neutropenia occur during treatment of HIV, discontinue concomitant marrow-toxic medications if possible, and treat coexisting iron deficiency, opportunistic infections, and/or malignancies; persistent, severe anemia or neutropenia may require changing the antiretroviral regimen. If significant anemia occurs during therapy for perinatal HIV prophylaxis, consult with a pediatric HIV expert to determine if early discontinuation should be considered. Zidovudine-related adverse hematologic effects may be concentration-dependent and associated with increasing AUC (Fillekes 2014; HHS [pediatric] 2023).
Adverse cardiac effects have been associated with zidovudine therapy. A prospective study of 325 pediatric patients aged 7 to 16 years with perinatally acquired HIV evaluated associations between previous or current antiretroviral agents and cardiac echocardiogram measures. When comparing patients currently receiving zidovudine (n=107) with those who were not, zidovudine therapy was associated with increased end-systolic wall stress and slightly larger heart size. Longer duration of zidovudine use was associated with higher wall stress (Williams 2018). A descriptive study evaluated 643 individuals 1 to 25 years of age with perinatally acquired HIV to determine prevalence of early cardiac dysfunction and reported that left ventricular ejection fraction was negatively associated with history of zidovudine exposure. Implications for cardiac outcomes later in life (eg, cardiomyopathy) are unknown (McCrary 2020; Williams 2018).
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral:
Retrovir: 100 mg [contains soybean lecithin]
Generic: 100 mg
Solution, Intravenous [preservative free]:
Retrovir: 10 mg/mL (20 mL)
Syrup, Oral:
Retrovir: 50 mg/5 mL (240 mL) [contains sodium benzoate; strawberry flavor]
Generic: 50 mg/5 mL (240 mL)
Tablet, Oral:
Generic: 300 mg
May be product dependent
Capsules (Retrovir Oral)
100 mg (per each): $3.24
Capsules (Zidovudine Oral)
100 mg (per each): $2.02
Solution (Retrovir Intravenous)
10 mg/mL (per mL): $1.75
Syrup (Retrovir Oral)
50 mg/5 mL (per mL): $0.32
Tablets (Zidovudine Oral)
300 mg (per each): $6.02
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Capsule, Oral:
Retrovir (AZT): 100 mg [DSC]
Generic: 100 mg
Solution, Intravenous:
Retrovir (AZT): 10 mg/mL (20 mL)
Syrup, Oral:
Retrovir (AZT): 10 mg/mL (240 mL) [contains sodium benzoate]
Oral: Administer without regard to meals.
IV: Avoid rapid infusion or bolus injection. Do not administer IM.
Infuse over 1 hour; in pregnant patients, infuse loading dose over 1 hour followed by continuous infusion.
Oral: May be administered without regard to meals; use calibrated measuring device to accurately measure oral liquid dose; for neonatal patients, graduations of 0.1 mL are necessary due to small dose volumes.
Parenteral: IV infusion: Administer over 1 hour; in neonates, dose may be infused over 30 minutes. Do not administer IM; do not administer IV push or by rapid infusion.
Hazardous agent (NIOSH 2016 [group 2]).
Use appropriate precautions for receiving, handling, storage, preparation, dispensing, transporting, administration, and disposal. Follow NIOSH and USP 800 recommendations and institution-specific policies/procedures for appropriate containment strategy (NIOSH 2016; USP-NF 2020).
Note: Facilities may perform risk assessment of some hazardous drugs to determine if appropriate for alternative handling and containment strategies (USP-NF 2020). Refer to institution-specific handling policies/procedures.
HIV-1 infection, treatment: Treatment of HIV-1 infection in combination with other antiretroviral agents
Perinatal HIV-1 transmission, prevention: Prevention of mother to fetus HIV-1 transmission
HIV-1 nonoccupational postexposure prophylaxis (nPEP)
Azidothymidine may be confused with azaTHIOprine, aztreonam
Retrovir may be confused with acyclovir, ritonavir
AZT is an error-prone abbreviation (mistaken as azathioprine, aztreonam)
Substrate of CYP2A6 (minor), CYP2C19 (minor), CYP2C9 (minor), CYP3A4 (minor), OAT1/3; Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
5-Aminosalicylic Acid Derivatives: May enhance the myelosuppressive effect of Myelosuppressive Agents. Risk C: Monitor therapy
Acemetacin: May enhance the adverse/toxic effect of Zidovudine. Specifically, the risk for hematologic toxicity may be increased. Risk C: Monitor therapy
Amodiaquine: Zidovudine may enhance the neutropenic effect of Amodiaquine. Management: Avoid coadministration of zidovudine-containing antiretroviral therapy with amodiaquine when possible. If combined, monitor closely for neutropenia. Risk D: Consider therapy modification
BCG (Intravesical): Myelosuppressive Agents may diminish the therapeutic effect of BCG (Intravesical). Risk X: Avoid combination
Betibeglogene Autotemcel: Antiretroviral Agents may diminish the therapeutic effect of Betibeglogene Autotemcel. Risk X: Avoid combination
Chloramphenicol (Ophthalmic): May enhance the adverse/toxic effect of Myelosuppressive Agents. Risk C: Monitor therapy
Chloramphenicol (Systemic): Myelosuppressive Agents may enhance the myelosuppressive effect of Chloramphenicol (Systemic). Risk X: Avoid combination
Cladribine: May enhance the myelosuppressive effect of Myelosuppressive Agents. Risk X: Avoid combination
Cladribine: Agents that Undergo Intracellular Phosphorylation may diminish the therapeutic effect of Cladribine. Risk X: Avoid combination
Clarithromycin: May enhance the myelosuppressive effect of Zidovudine. Clarithromycin may decrease the serum concentration of Zidovudine. Management: Monitor response to zidovudine closely when used with clarithromycin, and consider staggering zidovudine and clarithromycin doses when possible in order to minimize the potential for interaction. Risk D: Consider therapy modification
CloZAPine: Myelosuppressive Agents may enhance the adverse/toxic effect of CloZAPine. Specifically, the risk for neutropenia may be increased. Risk C: Monitor therapy
Deferiprone: Myelosuppressive Agents may enhance the neutropenic effect of Deferiprone. Management: Avoid the concomitant use of deferiprone and myelosuppressive agents whenever possible. If this combination cannot be avoided, monitor the absolute neutrophil count more closely. Risk D: Consider therapy modification
Dexketoprofen: May enhance the adverse/toxic effect of Zidovudine. Risk C: Monitor therapy
Dipyrone: May enhance the adverse/toxic effect of Myelosuppressive Agents. Specifically, the risk for agranulocytosis and pancytopenia may be increased Risk X: Avoid combination
DOXOrubicin (Conventional): May enhance the adverse/toxic effect of Zidovudine. DOXOrubicin (Conventional) may diminish the therapeutic effect of Zidovudine. Management: Avoid concomitant use of doxorubicin and zidovudine due to the possibility of reduced zidovudine efficacy and increased myelosuppressive effects. Risk D: Consider therapy modification
DOXOrubicin (Liposomal): May enhance the adverse/toxic effect of Zidovudine. DOXOrubicin (Liposomal) may diminish the therapeutic effect of Zidovudine. Management: Avoid concomitant use of doxorubicin and zidovudine. Reduced efficacy of zidovudine is possible based on in vitro data. Also, increased myelosuppressive effects are possible with combined administration. Risk D: Consider therapy modification
Elivaldogene Autotemcel: Antiretroviral Agents may diminish the therapeutic effect of Elivaldogene Autotemcel. Management: Avoid use of antiretroviral medications for at least one month, or for the amount of time required for elimination of the retroviral medication, prior to stem cell mobilization and until the all apheresis cycles are finished Risk X: Avoid combination
Fexinidazole: Myelosuppressive Agents may enhance the myelosuppressive effect of Fexinidazole. Risk X: Avoid combination
Ganciclovir-Valganciclovir: May enhance the adverse/toxic effect of Zidovudine. Specifically, hematologic toxicity may be enhanced. Risk C: Monitor therapy
Interferons: May enhance the adverse/toxic effect of Zidovudine. Interferons may decrease the metabolism of Zidovudine. Risk C: Monitor therapy
Levomethadone: May increase the serum concentration of Zidovudine. Risk C: Monitor therapy
Lopinavir: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Lovotibeglogene Autotemcel: Antiretroviral Agents may diminish the therapeutic effect of Lovotibeglogene Autotemcel. Risk X: Avoid combination
Methadone: May increase the serum concentration of Zidovudine. Risk C: Monitor therapy
Nelfinavir: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Nirmatrelvir and Ritonavir: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Olaparib: Myelosuppressive Agents may enhance the myelosuppressive effect of Olaparib. Risk C: Monitor therapy
Orlistat: May decrease the serum concentration of Antiretroviral Agents. Risk C: Monitor therapy
Probenecid: May increase the serum concentration of Zidovudine. Risk C: Monitor therapy
Promazine: May enhance the myelosuppressive effect of Myelosuppressive Agents. Risk C: Monitor therapy
Raltegravir: May enhance the myopathic (rhabdomyolysis) effect of Zidovudine. Risk C: Monitor therapy
Ribavirin (Oral Inhalation): Zidovudine may enhance the adverse/toxic effect of Ribavirin (Oral Inhalation). Specifically, the risk/severity of anemia may be increased. Management: Due to significantly increased risk of anemia, consider even closer monitoring for anemia than routinely recommended. Alternative therapies should be considered when clinically possible, particularly for patients with other risk factors. Risk D: Consider therapy modification
Ribavirin (Systemic): Zidovudine may enhance the adverse/toxic effect of Ribavirin (Systemic). Specifically, the risk/severity of anemia may be increased. Management: Due to significantly increased risk of anemia, consider even closer monitoring for anemia than routinely recommended for ribavirin. Alternative therapies should be considered when clinically possible, particularly for patients with other risk factors. Risk D: Consider therapy modification
RifAMPin: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Ritonavir: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Ropeginterferon Alfa-2b: Myelosuppressive Agents may enhance the myelosuppressive effect of Ropeginterferon Alfa-2b. Management: Avoid coadministration of ropeginterferon alfa-2b and other myelosuppressive agents. If this combination cannot be avoided, monitor patients for excessive myelosuppressive effects. Risk D: Consider therapy modification
Stavudine: Zidovudine may diminish the therapeutic effect of Stavudine. Risk X: Avoid combination
Tenoxicam: May enhance the adverse/toxic effect of Zidovudine. Risk C: Monitor therapy
Tipranavir: May decrease the serum concentration of Zidovudine. Risk C: Monitor therapy
Trimethoprim: Zidovudine may enhance the neutropenic effect of Trimethoprim. Trimethoprim may increase the serum concentration of Zidovudine. Risk C: Monitor therapy
Valproate Products: May increase the serum concentration of Zidovudine. Risk C: Monitor therapy
Contraception is not required to initiate or continue antiretroviral therapy.
The US department of Health and Human Services (HHS) perinatal HIV guidelines consider zidovudine an alternative nucleoside reverse transcriptase inhibitor for patients with HIV who are not yet pregnant but are trying to conceive.
Maximum viral suppression sustained below the limits of detection prior to conception is recommended for all persons with HIV who are planning a pregnancy. Optimization of the health of the person who will become pregnant is recommended. Selection of or changes to a specific antiretroviral regimen prior to pregnancy should be done as part of a shared decision-making process. In most cases, recommendations from the HHS perinatal HIV guidelines (based on data obtained from cisgender women) can be applied to transgender and gender-diverse people assigned female sex at birth.
Health care providers caring for couples planning a pregnancy when one or both partners are diagnosed with HIV may contact the National Perinatal HIV Hotline (1-888-448-8765) for clinical consultation (HHS [perinatal] 2023).
Zidovudine has a high level of transfer across the human placenta; the placenta also metabolizes zidovudine to the active metabolite.
No increased risk of overall teratogenic effects has been observed following first trimester exposure according to data collected by the antiretroviral pregnancy registry. Maternal antiretroviral therapy (ART) may be associated with adverse pregnancy outcomes including preterm birth, low birth weight, and small-for-gestational-age infants. Actual risks may be influenced by maternal factors, such as disease severity, GA at initiation of therapy, and specific ART regimen; therefore, close fetal monitoring is recommended. Because there is clear benefit to appropriate treatment, maternal ART should not be withheld due to concerns for adverse neonatal outcomes. Long-term follow-up is recommended for all infants exposed to antiretroviral medications; children not diagnosed with HIV but who were exposed to ART in utero or as a neonate and develop significant organ system abnormalities of unknown etiology (particularly of the CNS or heart) should be evaluated for potential metabolic dysfunction.
The US Department of Health and Human Services (HHS) perinatal HIV guidelines consider zidovudine an alternative nucleoside reverse transcriptase inhibitor for pregnant patients with HIV who are antiretroviral-naive, who have had ART therapy in the past but are restarting, or who require a new ART regimen (due to poor tolerance or poor virologic response of current regimen). In addition, patients who become pregnant while taking zidovudine may continue if viral suppression is effective and the regimen is well tolerated.
The pharmacokinetics of zidovudine are not significantly altered in pregnancy and dose adjustment is not needed.
Recommendations for use of intrapartum zidovudine are based on maternal HIV RNA levels assessed at 36 weeks' gestation or within 4 weeks of delivery, and other factors. Intrapartum zidovudine IV is recommended when HIV RNA is >1,000 copies/mL or when the HIV RNA level is unknown near delivery. Intrapartum zidovudine IV should also be administered if a lack of adherence is suspected since the last RNA result or when HIV is initially diagnosed during labor. Patients with HIV RNA >1,000 copies/mL should be given zidovudine even in cases of documented zidovudine resistance unless there is a history of hypersensitivity. Intrapartum zidovudine IV is not needed in patients receiving ART who have HIV RNA <50 copies/mL within 4 weeks of delivery AND who are adherent to their ART regimen. If a fetal scalp electrode is needed during labor, consider the fetal risk of HIV transmission high even if maternal HIV RNA is <50 copies/mL. The decision to administer zidovudine IV intrapartum to patients with HIV RNA ≥50 and ≤1,000 copies/mL within 4 weeks of delivery should be made on a case-by-case basis, and consider consistency in maintaining an undetectable viral load in the third trimester, compliance with prenatal care, or concerns with adherence.
ART is recommended for all pregnant people with HIV to maximize their health, maintain the viral load below the limit of detection, and reduce the risk of perinatal transmission. Selection of or changes to a specific antiretroviral regimen during pregnancy should be done as part of a shared decision-making process. Patients on fully suppressive regimens prior to pregnancy generally may continue the same regimen considering known pregnancy outcomes and pharmacokinetic data. Monitoring of patients who are pregnant is more frequent than in patients who are not pregnant. ART initiated during pregnancy can be modified after delivery. In most cases, recommendations from the HHS perinatal HIV guidelines (based on data obtained from cisgender women) can be applied to transgender and gender-diverse people assigned female sex at birth.
Data collection to monitor pregnancy and infant outcomes following exposure to ART is ongoing. Health care providers should enroll all patients exposed to antiretroviral medications during pregnancy in the Antiretroviral Pregnancy Registry (1-800-258-4263). Enrollment should be done as early in pregnancy as possible.
Health care providers caring for pregnant patients with HIV and their infants may contact the National Perinatal HIV Hotline (1-888-448-8765) for clinical consultation (HHS [perinatal] 2023).
Zidovudine is present in breast milk.
Concentrations of zidovudine in breast milk may be similar to those in the maternal serum. Zidovudine has not been detected in the serum of breastfeeding infants exposed via breast milk.
Maintaining maximum viral suppression during pregnancy and postpartum decreases but does not eliminate the risk of HIV transmission via breast milk. In addition, multiclass-resistant virus has been detected in breastfeeding infants who acquire HIV despite maternal therapy. In the United States, where formula is usually accessible, affordable, safe, and sustainable, and the risk of infant mortality due to diarrhea and respiratory infections is low, the US Department of Health and Human Services perinatal HIV guidelines do not recommend breastfeeding for patients with HIV when safer infant feeding options are available. Persons with HIV who maintain an undetectable viral load while taking antiretroviral therapy (ART) should evaluate infant feeding options (formula, banked donor milk, or breastfeeding) as part of a shared decision-making process (if breastfeeding is being considered, see guidelines for measures to reduce the risk of HIV transmission). When the HIV status at delivery is not known, breast milk may be expressed and stored until a negative test is available. If HIV infection is diagnosed after breastfeeding has been initiated, breastfeeding should be discontinued immediately. Breastfeeding is not recommended for persons with HIV who are not taking ART and/or who do not have sustained viral suppression.
Information is available for counseling and managing patients with HIV who are considering breastfeeding (1-888-448-8765). In most cases, recommendations from the HHS perinatal HIV guidelines (based on data obtained from cisgender women) can be applied to transgender and gender diverse people assigned female sex at birth (HHS [perinatal] 2023).
CBC with differential (more frequent monitoring required in patients with poor bone marrow reserve); LFTs; serum creatinine; HIV viral load and CD4 count.
Zidovudine is a thymidine analog which interferes with the HIV viral RNA-dependent DNA polymerase resulting in inhibition of viral replication; nucleoside reverse transcriptase inhibitor
Note: In general, pharmacokinetic data for pediatric patients >3 months to 12 years of age are similar to data in adult patients.
Absorption: Oral: Well absorbed
Distribution: Significant penetration into the CSF
Vd: 1 to 2.2 L/kg
CSF/plasma ratio:
Infants 3 months to Children 12 years (n=38): Median: 0.68; Range: 0.03 to 3.25
Adults (n=39): Median: 0.6; Range: 0.04 to 2.62
Protein binding: 25% to 38%
Metabolism: Hepatic via glucuronidation to inactive metabolites, including GZDV; extensive first-pass effect
Bioavailability: Oral: Similar for tablets, capsules, and syrup
Neonates <14 days: 89%
Infants 14 days to 3 months: 61%
Infants 3 months to Children 12 years: 65%
Adults: 64% ± 10%
Half-life elimination: Terminal:
Premature neonate: 6.3 hours
Full-term neonates: 3.1 hours
Infants 14 days to 3 months: 1.9 hours
Infants 3 months to Children 12 years: 1.5 hours
Adults: 0.5 to 3 hours (mean 1.1 hours)
Time to peak, serum: 30 to 90 minutes
Excretion:
Oral: Urine (72% to 74% as metabolites, 14% to 18% as unchanged drug)
IV: Urine (45% to 60% as metabolites, 18% to 29% as unchanged drug)
Altered kidney function: Cl is decreased, resulting in an increased half-life and AUC of zidovudine and major metabolite GZDV.
Hepatic function impairment: Clearance is decreased and plasma concentrations are increased.
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