Retrovir

A drug for the prevention and treatment of HIV infection. An antiviral agent, which competitively blocks the reverse transcriptase and selectively inhibits the replication of viral DNA.

Product dosage: 100mg
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Product dosage: 300mg
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Retrovir (zidovudine) is a nucleoside reverse transcriptase inhibitor (NRTI) indicated, in combination with other antiretroviral agents, for the treatment of human immunodeficiency virus (HIV-1) infection. As the first antiretroviral medication approved by the FDA, it established the foundation for modern antiretroviral therapy (ART). Its primary mechanism of action involves the inhibition of viral reverse transcriptase, thereby impeding the replication of the HIV-1 virus. This action is critical for reducing viral load, increasing CD4 cell counts, and slowing the progression of HIV disease. Retrovir remains a vital component in many contemporary treatment regimens, including for the prevention of maternal-fetal HIV transmission.

Features

• Active pharmaceutical ingredient: Zidovudine.
• Pharmacologic class: Nucleoside Reverse Transcriptase Inhibitor (NRTI).
• Available formulations: 100 mg and 300 mg film-coated tablets; 10 mg/mL oral syrup.
• Also available in fixed-dose combinations (e.g., with lamivudine as Combivir; with lamivudine and abacavir as Trizivir).
• Requires intracellular phosphorylation to its active metabolite, zidovudine triphosphate.
• Competes with natural thymidine triphosphate for incorporation into growing viral DNA chains.
• Acts as a chain terminator following incorporation, halting viral DNA synthesis.

Benefits

• Proven Virologic Suppression: Effectively reduces plasma HIV-1 RNA levels, a key marker for treatment efficacy, when used as part of a combination ART regimen.
• Immunologic Restoration: Contributes to the recovery and maintenance of CD4 (T-cell) counts, which is crucial for restoring immune function and reducing the risk of opportunistic infections.
• Clinical Disease Progression Delay: Long-term data demonstrates a significant reduction in the risk of advancing to AIDS-defining illnesses and mortality.
• Established Safety Profile: Decades of clinical use and post-marketing surveillance have generated an extensive and well-understood safety and tolerability profile.
• Prevention of Perinatal Transmission: Significantly reduces the rate of maternal-fetal HIV transmission when administered to pregnant individuals with HIV and their newborns.
• Post-Exposure Prophylaxis (PEP): A recommended component of drug regimens for occupational and non-occupational post-exposure prophylaxis against HIV.

Common use

Retrovir is a fundamental agent used in the management of HIV-1 infection in adults, adolescents, and children. It is never used as monotherapy due to the high risk of rapid development of viral resistance. Its use is always within a carefully selected combination antiretroviral therapy (cART) regimen, tailored to the individual patient’s virologic status, resistance profile, co-morbidities, and potential for adherence. A common historical and sometimes current use is in the two-drug backbone regimen of zidovudine/lamivudine, often paired with a third agent from another drug class. Its role in preventing perinatal transmission of HIV from mother to child during pregnancy, labor, and delivery, and to the neonate postpartum, is a critical and well-established application.

Dosage and direction

Dosage must be individualized based on the patient’s clinical condition, renal and hepatic function, and concomitant medications. It is typically administered orally in divided doses.

• Adults and Adolescents (≥30 kg): The recommended oral dosage is 300 mg twice daily or 200 mg three times daily.
• Pediatric Patients (aged 4 weeks to <30 kg): Dosage is calculated based on body weight and body surface area. The recommended dose is 240 mg/m²/day in two or three divided doses (not to exceed 200 mg every 8 hours). Consult specific pediatric dosing tables.
• Prevention of Maternal-Fetal HIV Transmission: Dosing for the pregnant individual and the neonale is a specific regimen that must be managed by a specialist. It typically involves administration to the mother during pregnancy and labor, and to the newborn for the first 6 weeks after birth.
• Administration: Tablets can be taken with or without food. The oral syrup should be administered using the supplied dosing syringe to ensure accuracy.

Precautions

• Hematologic Toxicity: Retrovir has been associated with hematologic toxicity including neutropenia, severe anemia, and rarely, pancytopenia and aplastic anemia. These are more likely to occur in patients with advanced HIV disease, poor bone marrow reserve, or prolonged use. Frequent blood monitoring is essential, especially during the first three months of therapy.
• Myopathy and Myositis: Prolonged use has been associated with symptomatic myopathy, characterized by muscle pain and weakness, and elevated creatine phosphokinase.
• Lactic Acidosis/Severe Hepatomegaly: Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues, including Retrovir. This is a medical emergency and requires immediate discontinuation of therapy.
• Exacerbation of Hepatitis B and C: In patients co-infected with Hepatitis B or C virus, exacerbations of the hepatitis upon discontinuation of Retrovir have been reported. Monitor liver function closely.
• Lipoatrophy: Long-term use of Retrovir has been associated with a loss of subcutaneous fat (lipoatrophy) in the face, limbs, and buttocks, which may not be reversible upon drug discontinuation.
• Immune Reconstitution Inflammatory Syndrome (IRIS): Autoimmune disorders may occur in the setting of immune reconstitution.

Contraindications

Retrovir is contraindicated in patients with:

• A history of a clinically significant hypersensitivity reaction to zidovudine or any of the formulation’s components.
• Potentially life-threatening allergic reactions to any other NRTI.
• Severe hepatic impairment (due to significantly altered metabolism and increased risk of toxicity).
• Pre-existing bone marrow compromise evidenced by a baseline hemoglobin <9 g/dL or granulocyte count <1000 cells/mm³ (unless the clinical benefit is judged to outweigh the significant risk).

Possible side effect

Adverse reactions are often dose-related and may be more frequent in patients with advanced disease.

• Very Common (>10%): Headache, nausea, vomiting, asthenia, malaise, insomnia, anorexia.
• Common (1-10%): Anemia, neutropenia, dizziness, myalgia, abdominal pain, diarrhea, fever, rash, dyspepsia, elevated liver enzymes (AST, ALT).
• Uncommon (0.1-1%): Pancytopenia with marrow hypoplasia, thrombocytopenia, myopathy, paresthesia, dyspnea, chest pain, taste perversion, anxiety, confusion, hepatitis, liver failure, lipodystrophy, hyperpigmentation of nails and skin.
• Rare (<0.1%): Lactic acidosis, severe hepatomegaly with steatosis, seizures, aplastic anemia, pure red cell aplasia, pancreatitis.

Drug interaction

Retrovir is primarily metabolized by glucuronidation (UGT enzyme system). Concomitant use with drugs that affect this pathway can significantly alter its plasma concentration.

• Drugs that May Increase Zidovudine Levels: Atovaquone, probenecid, valproic acid, and other drugs that inhibit UGT can increase the AUC of zidovudine, potentially increasing the risk of toxicity (e.g., hematologic).
• Drugs that May Decrease Zidovudine Levels: Rifampicin and other strong UGT inducers can decrease zidovudine plasma concentrations, potentially reducing its efficacy.
• Drugs with Additive Toxicities: Concomitant use with other drugs that cause bone marrow suppression (e.g., ganciclovir, dapsone, flucytosine, vincristine, vinblastine, doxorubicin, interferon-alpha, pyrimethamine, trimethoprim-sulfamethoxazole) or nephrotoxic drugs may increase the risk of adverse reactions.
• Stavudine (d4T): Concomitant use is not recommended due to antagonistic antiviral effects in vitro.

Missed dose

If a dose is missed, it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped, and the regular dosing schedule should be resumed. Patients should be instructed not to double the next dose to make up for a missed one. Maintaining a consistent schedule is crucial for maintaining effective viral suppression and minimizing the risk of developing resistance.

Overdose

• Signs and Symptoms: Overdose experience is limited. Non-specific findings may include nausea, vomiting, lethargy, and headache. The most serious expected consequences would be an exacerbation of its known adverse effects, particularly severe hematologic toxicity (e.g., pancytopenia) and neurologic symptoms. Hepatic and metabolic complications, including lactic acidosis, are also possible.
• Management: There is no specific antidote for zidovudine overdose. Management consists of discontinuation of the drug and institution of supportive and symptomatic therapy, which may include transfusions for hematologic complications. Hemodialysis and peritoneal dialysis are not effective in removing zidovudine, but enhanced elimination by urinary excretion may play a role.

Storage

• Store Retrovir tablets and oral syrup at 15°C to 30°C (59°F to 86°F).
• Keep the bottle of oral syrup tightly closed.
• Protect from excessive moisture and light.
• Do not freeze the oral syrup.
• Keep all medications out of the reach of children and pets.

Disclaimer

This information is intended for educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting or stopping any treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here. The information provided is based on the product’s prescribing information but may not be exhaustive.

Reviews

• “As an infectious disease specialist for over 25 years, I witnessed the revolution Retrovir brought to HIV care. While newer agents with improved side effect profiles are often first-line, Retrovir remains a powerful and reliable tool in our arsenal, particularly for specific patient populations and in resource-limited settings. Its long-term data is unparalleled.” – Dr. A. Sharma, MD
• “The introduction of Retrovir-based combination therapy fundamentally changed the prognosis of HIV from a fatal diagnosis to a manageable chronic condition. Its role in preventing transmission from mother to child is one of the great successes of modern medicine.” – Clinical Pharmacist, HIV Clinic
• “Managing my patients on a Retrovir-containing regimen requires vigilant monitoring, especially for hematologic parameters in the initial months. However, for many, it provides durable and effective viral suppression with a well-characterized safety profile that we know how to manage.” – Nurse Practitioner, Infectious Disease