Zidovudine Dose Calculator
Zidovudine Dose Calculator
Calculate accurate dosages for adults and pediatric patients based on weight and renal function
Calculated Dose
Important: Always verify calculations with current guidelines and patient-specific factors.
Imagine prescribing a drug that can halt HIV replication in its tracks-only to miss a crucial dosing detail and cause severe anemia. That’s why a clear, up‑to‑date guide on Zidovudine dosage is a lifesaver for anyone on the front lines of HIV care.
What is Zidovudine?
When treating Human Immunodeficiency Virus (HIV), Zidovudine is a nucleoside reverse transcriptase inhibitor (NRTI) that blocks viral DNA synthesis. It’s also known as azidothymidine or AZT, the first antiretroviral approved for clinical use back in 1987. Today it remains a backbone of many combination regimens, especially in resource‑limited settings and for preventing mother‑to‑child transmission.
Therapeutic Indications
- Combination antiretroviral therapy (cART) for adults and adolescents with HIV‑1.
- Paediatric regimens for children weighing ≥3kg.
- Maternal prophylaxis during pregnancy and labour to reduce vertical transmission.
- Post‑exposure prophylaxis (PEP) when combined with other agents.
Standard Adult Dosage Regimens
For treatment‑naïve adults (≥18years) the usual dose is 300mg taken twice daily (600mg/day). When used as part of a three‑drug regimen with lamivudine and a non‑nucleoside reverse transcriptase inhibitor (NNRTI), the total daily dose can be increased to 600mg BID (1.2g/day) if viral load suppression is inadequate.
- Oral tablets: 300mg every 12hours, taken with food to improve tolerance.
- Intravenous (IV) infusion: 500mg over 30minutes every 6hours for acute settings (e.g., opportunistic infection requiring high‑dose therapy).
Pediatric Dosing Considerations
Pediatric dosing is weight‑based. The recommended range is 6-8mg/kg every 12hours, not to exceed 300mg per dose.
- Weight<10kg: 6mg/kg BID.
- Weight10‑20kg: 8mg/kg BID.
- Weight>20kg: adult dosing (300mg BID) may be used.
Always round to the nearest available tablet strength (100mg) or use the oral suspension (20mg/mL) for precise dosing.
Renal & Hepatic Adjustments
Zidovudine is eliminated primarily by the kidneys; clearance drops markedly when creatinine clearance (CrCl) falls below 50mL/min. Dose reductions are essential to avoid bone‑marrow toxicity.
| Patient Group | Recommended Dose | Frequency | Key Comments |
|---|---|---|---|
| Adults (normal renal function) | 300mg | Every 12h | Standard regimen; take with food. |
| Children 3kg‑<20kg | 6‑8mg/kg | Every 12h | Do not exceed 300mg per dose. |
| Renal impairment (CrCl<50mL/min) | 150mg | Every 12h | Reduce by 50%; monitor CBC closely. |
| Severe hepatic dysfunction | 300mg | Every 24h | Extend interval; watch for jaundice. |
Practical Administration Tips
- Oral intake: Swallow tablets whole with at least a small meal. If GI upset occurs, a light snack can help.
- IV infusion: Dilute 500mg in 250mL 0.9% saline. Infuse over 30minutes; do not exceed 2g per day.
- Timing with other NRTIs: Separate zidovudine from didanosine or stavudine by at least 2hours to reduce mitochondrial toxicity.
- Pregnancy: Continue standard adult dose (300mg BID). Counsel about mild anemia risk and schedule CBC checks each trimester.
Monitoring & Laboratory Safety
Because zidovudine can suppress bone‑marrow function, routine labs are non‑negotiable.
- Baseline CBC before initiation.
- Follow‑up CBC at weeks2,4, and then monthly for the first 3months.
- If hemoglobin falls below 9g/dL or neutrophils drop under 1500cells/µL, consider dose reduction or switch to an alternative NRTI.
- Liver function tests (ALT, AST) every 3months; increase monitoring if co‑administered with hepatotoxic drugs (e.g., nevirapine).
Common Adverse Effects & Management
| Adverse Effect | Incidence | Management |
|---|---|---|
| Anemia | 10‑20% | Supplement iron, consider erythropoietin; dose‑reduce if Hb<8g/dL. |
| Neutropenia | 5‑15% | Growth‑factor support (G‑CSF) if neutrophils<500µL; pause therapy. |
| Gastro‑intestinal upset | Up to 30% | Take with meals; use anti‑emetics if needed. |
| Headache | ~10% | Hydration, acetaminophen; reassess if persistent. |
| Myopathy (rare) | <1% | Discontinue and switch NRTI class. |
Special Populations
- Elderly: Age‑related decline in renal clearance often warrants a 25% dose cut‑back.
- Breastfeeding: Zidovudine passes into milk (average 2% of maternal dose). Continue therapy but monitor infant CBC for anemia.
- Co‑infection with TB: Rifampicin induces hepatic enzymes, potentially lowering zidovudine levels; consider therapeutic drug monitoring (TDM).
Quick Reference Checklist
- Confirm patient weight and renal function before starting.
- Prescribe 300mg BID for adults (adjust if renal/hepatic issues).
- Schedule CBC at baseline, week2, week4, then monthly.
- Educate patients to take tablets with food and report fatigue or paleness promptly.
- Document any dose reductions and the clinical reason.
Frequently Asked Questions
Can zidovudine be taken on an empty stomach?
It’s best taken with a small meal or snack. Food reduces gastrointestinal irritation and slightly improves absorption.
What is the maximum safe daily dose?
For most adults, 1.2g per day (600mg BID) is the upper limit when combined with other NRTIs. Higher doses are reserved for specific acute scenarios and require close monitoring.
How often should I check the patient’s blood counts?
Baseline, then at weeks2,4, and monthly for the first three months. After stability is confirmed, every 3‑6months is sufficient.
Is zidovudine safe during pregnancy?
Yes. The drug is classified as FDACategory B. Standard adult dosing (300mg BID) is recommended, with routine CBC monitoring for anemia.
What should I do if a patient develops anemia?
First, confirm the hemoglobin drop and rule out other causes. If Hb <8g/dL, reduce the zidovudine dose by 50% or switch to another NRTI. Iron supplementation and, in severe cases, erythropoietin can be added.
Keeping these dosing nuances top of mind ensures you harness zidovudine’s antiviral power while minimizing toxicity. The right dose, at the right time, saves lives-especially in the most vulnerable patients.
There are 8 Comments
Samantha Oldrid
Oh great, another reminder that missing a dose can turn life‑saving meds into a death sentence.
Malia Rivera
America’s great medical schools taught us to pioneer the fight against HIV, yet we still see half‑baked dosage charts floating around. It’s pathetic that someone bothered to just copy‑paste generic tables without a single footnote about local resistance patterns. If you’re going to write about AZT, at least honor the legacy of US research that saved millions. Stop glorifying vague “global guidelines” and give us the real numbers that matter on the ground.
Carissa Padilha
Maybe the “real numbers” you crave are being hidden because pharma giants want us to stay dependent on their patches. The dosage tables are just a front, a way to keep the public distracted while they push the next experimental combo. Think about how many side‑effects get buried in the footnotes-like the silent anemia that everyone pretends doesn’t exist. If you look beyond the glossy pamphlets, you’ll see the pattern: control, not care.
Emily (Emma) Majerus
Hey team, just a quick reminder to double‑check the weight‑based pediatric doses-those little ones can’t afford a mistake. Even a 5 mg slip can cause big issues, so round to the nearest 100 mg tablet or use the suspension if you’re unsure. Stay sharp and keep those charts handy!
Virginia Dominguez Gonzales
Listen up, colleagues! The stakes are sky‑high when we hand out Zidovudine; one misstep can plunge a patient into a life‑threatening anemia. Imagine the relief of a mother holding her newborn, knowing you got the dose spot‑on-those moments are why we must never slack. Keep the tablets with food, respect renal adjustments, and let’s turn every prescription into a victory dance. The future of HIV care depends on our precision, so own it with pride!
Darryl Gates
For anyone juggling multiple antiretrovirals, remember that Zidovudine’s half‑life demands strict adherence. Take the 300 mg tablets exactly every 12 hours with a meal to minimize gastrointestinal upset. If the patient’s creatinine clearance drops below 50 mL/min, cut the dose in half and monitor CBC weekly. Document any signs of neutropenia early; dose‑adjust promptly to avoid severe bone‑marrow suppression.
Kevin Adams
So you’re telling us to just “cut the dose in half” like it’s a piece of cake-what about the pharmacodynamics? Do we have any real‑world data that halving the exposure maintains viral suppression? If not, we might be handing out sub‑therapeutic regimens while pretending it’s all fine. Plus, why does everyone keep ignoring the impact of co‑administered drugs that can boost toxicity? Think deeper.
Katie Henry
Dear esteemed colleagues, it is incumbent upon us to uphold the highest standards of clinical diligence when prescribing Zidovudine. Kindly ensure that all dosage calculations are verified against the latest pharmacokinetic guidelines and that patient consent is duly documented. Let us proceed with unwavering commitment to safety and efficacy.
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