ZERIT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZERIT (ZERIT).
Nucleoside reverse transcriptase inhibitor (NRTI); after intracellular phosphorylation to stavudine triphosphate, it competes with natural substrate deoxythymidine triphosphate for incorporation into viral DNA, causing chain termination.
| Metabolism | Undergoes intracellular phosphorylation to the active triphosphate; eliminated renally (approximately 40% unchanged in urine) and partially metabolized via non-cytochrome P450 pathways. |
| Excretion | Renal: approximately 67% (as unchanged drug) via glomerular filtration and active tubular secretion; biliary/fecal: minor (<10%) |
| Half-life | Terminal elimination half-life: 1.0–1.6 hours (mean 1.2 h) in adults with normal renal function; prolonged to 3.5–8.0 hours in renal impairment (CrCl <50 mL/min) requiring dose adjustment |
| Protein binding | Negligible: <5% bound to plasma proteins (primarily albumin) |
| Volume of Distribution | 0.5–0.6 L/kg; indicates distribution into total body water with extensive intracellular penetration |
| Bioavailability | Oral: 86.4% (range 79–99%) for capsules; oral solution bioequivalent with comparable absorption |
| Onset of Action | Oral: peak plasma concentrations achieved within 0.5–1.5 hours; antiviral effect detectable within 1–2 weeks of continuous therapy |
| Duration of Action | Intracellular active metabolite (stavudine triphosphate) has a half-life of 3.5–7 hours; clinical effect persists with twice-daily dosing due to intracellular accumulation |
| Molecular Weight | 224.22 |
Adults and adolescents (≥13 years, ≥60 kg): 40 mg orally twice daily. Adults and adolescents (≥13 years, <60 kg): 30 mg orally twice daily.
| Dosage form | FOR SOLUTION |
| Renal impairment | Creatinine clearance (CrCl) ≥50 mL/min: no adjustment. CrCl 26-49 mL/min: 20 mg every 12 hours (≥60 kg) or 15 mg every 12 hours (<60 kg). CrCl 10-25 mL/min: 20 mg every 24 hours (≥60 kg) or 15 mg every 24 hours (<60 kg). Hemodialysis: 20 mg every 24 hours (≥60 kg) or 15 mg every 24 hours (<60 kg), administer after dialysis. |
| Liver impairment | No specific adjustments for hepatic impairment; use with caution in severe hepatic disease. |
| Pediatric use | Newborns (0-13 days): 2 mg/kg/dose orally every 12 hours. Infants and children (14 days to <13 years, BSA not available): weight-based: 1 mg/kg/dose every 12 hours if <30 kg; 30 mg every 12 hours if ≥30 kg. Alternatively, BSA-based: 240 mg/m²/day divided every 12 hours. |
| Geriatric use | Consider age-related renal impairment; adjust dose based on CrCl as per renal adjustment guidelines. |
| 1st trimester | Use only if clearly needed; insufficient human data but animal studies show risk. |
| 2nd trimester | Use only if clearly needed; may cause lactic acidosis and hepatic steatosis. |
| 3rd trimester | Use with caution; may cause lactic acidosis and hepatic steatosis; risk of mitochondrial toxicity in neonates. |
Clinical note
Comprehensive clinical and safety monograph for ZERIT (ZERIT).
| Placental transfer | Stavudine crosses the placenta; cord blood concentrations are approximately 50% of maternal plasma levels. |
| Breastfeeding | Zerit (stavudine) is excreted into human breast milk in low concentrations. The potential for HIV transmission via breastfeeding remains, and guidelines recommend avoiding breastfeeding in HIV-positive mothers in developed countries. In resource-limited settings, benefits may outweigh risks under medical supervision. |
■ FDA Black Box Warning
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination, including stavudine.
| Serious Effects |
Hypersensitivity to stavudine or any componentLactic acidosis or severe hepatomegaly with steatosisSevere peripheral neuropathy
| Precautions | Lactic acidosis/hepatomegaly with steatosis; pancreatitis; peripheral neuropathy; lipodystrophy; immune reconstitution syndrome; hepatotoxicity; monitoring of liver function tests, serum lactate, and amylase. |
| Food/Dietary | No significant food interactions. Take with or without food. Avoid high-fat meals if GI upset occurs. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Zerit (stavudine) is classified as FDA Pregnancy Category C. Animal studies have shown evidence of embryotoxicity and teratogenicity (skeletal malformations) at doses 399 times the human exposure. Human data are limited; however, first-trimester exposure has been associated with an increased risk of congenital anomalies in some cohort studies, though not consistently. Nucleoside analogues are known to cause mitochondrial toxicity, which may affect fetal development. Use only if benefit outweighs risk, and consider alternative antiretrovirals with more safety data during pregnancy. |
| Fetal Monitoring | Monitor maternal liver function tests, complete blood count, lactate levels (risk of lactic acidosis/hepatic steatosis), and renal function. Fetal monitoring includes serial ultrasounds for growth and anatomy, particularly if first-trimester exposure occurred. Monitor for signs of fetal distress or preterm labor. After birth, monitor infant for hyperlactatemia and hematologic abnormalities. |
| Fertility Effects | Stavudine has been associated with reversible sperm abnormalities in animal studies and case reports of decreased sperm count and motility in men. In women, no significant impact on fertility has been reported, but nucleoside reverse transcriptase inhibitors may cause mitochondrial dysfunction in oocytes. Data are limited. |
| Clinical Pearls |
| Monitor for peripheral neuropathy, which may be irreversible. Adjust dose for renal impairment (CrCl <50 mL/min). Avoid co-administration with didanosine or hydroxyurea due to increased toxicity risk. ZERIT is contraindicated with ribavirin due to mitochondrial toxicity. |
| Patient Advice | Take exactly as prescribed, with or without food. Do not miss doses. · Report numbness, tingling, or pain in hands/feet immediately. · Avoid alcohol as it may worsen liver side effects. · Inform all healthcare providers of HIV therapy before any new medication. · Do not stop or change dose without consulting your doctor. |