ZERIT XR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZERIT XR (ZERIT XR).
ZERIT XR (stavudine extended-release) is a nucleoside analog reverse transcriptase inhibitor (NRTI). It is phosphorylated intracellularly to stavudine triphosphate, which competes with natural thymidine triphosphate for incorporation into viral DNA, causing chain termination and inhibition of HIV-1 reverse transcriptase.
| Metabolism | Stavudine is phosphorylated intracellularly to active metabolite; it is not significantly metabolized by cytochrome P450 enzymes. Approximately 40% of an oral dose is excreted unchanged in urine via glomerular filtration and active tubular secretion. |
| Excretion | Approximately 94% of the dose is excreted unchanged in urine via glomerular filtration and tubular secretion; <1% is eliminated in feces. |
| Half-life | 5.7 hours (range 4–8 hours) in patients with normal renal function; prolonged to 13–20 hours in renal impairment (CrCl <30 mL/min). |
| Protein binding | <5% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 0.83–1.14 L/kg (total body water distribution); extensive tissue penetration including CSF, semen, and fetal tissues. |
| Bioavailability | 68–89% after oral administration (mean 86%); food slightly delays absorption but no significant change in AUC. |
| Onset of Action | Peak plasma concentrations achieved 1.5–3 hours after oral administration; antiretroviral effect begins with first dose but maximal viral suppression takes weeks. |
| Duration of Action | Dosing interval 12 hours due to short half-life; clinical effect requires consistent adherence. For XR formulation, dosing interval is 24 hours. |
ZERIT XR (stavudine extended-release) is administered orally once daily. Adult dose: 100 mg once daily for patients ≥60 kg; 75 mg once daily for patients <60 kg.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | Creatinine clearance (CrCl) >50 mL/min: no adjustment. CrCl 26-50 mL/min: 50 mg once daily (if ≥60 kg) or 30 mg once daily (if <60 kg). CrCl 10-25 mL/min: 50 mg once daily (if ≥60 kg) or 30 mg once daily (if <60 kg). CrCl <10 mL/min or hemodialysis: 50 mg once daily (if ≥60 kg) or 30 mg once daily (if <60 kg) for patients not on dialysis; for hemodialysis, administer after dialysis. |
| Liver impairment | No specific guidelines for Child-Pugh classification. Use with caution in hepatic impairment; consider dose reduction or alternative therapy due to potential for hepatotoxicity. |
| Pediatric use | Weight-based dosing for ZERIT XR not established; use immediate-release stavudine. For IR: 1 mg/kg/dose twice daily (maximum 30 mg/dose) for <30 kg; 30 mg twice daily for ≥30 kg. |
| Geriatric use | Elderly patients may have age-related renal impairment; adjust dose based on creatinine clearance. Monitor renal function and neuropathy risk. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZERIT XR (ZERIT XR).
| Breastfeeding | Stavudine is excreted in human breast milk; milk-to-plasma ratio (M/P) is approximately 0.4. Due to potential for HIV transmission via breastfeeding and possibility of adverse effects (mitochondrial toxicity, lactic acidosis, neuropathy), HIV-infected mothers should not breastfeed. For non-HIV indications, weigh benefits against risks. |
| Teratogenic Risk | FDA Pregnancy Category C. Stavudine crosses the placenta. First trimester: limited human data, but animal studies show decreased fetal weight and increased incidence of skeletal variations at doses producing maternal toxicity. Second and third trimesters: no evidence of teratogenicity in prospective cohort studies, but mitochondrial toxicity may occur with prolonged exposure. Not recommended for use in pregnancy unless benefit outweighs risk; preferred alternatives (e.g., zidovudine) exist. |
■ FDA Black Box Warning
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination, including stavudine. Fatal lactic acidosis has been reported in pregnant women who received stavudine and didanosine with other antiretroviral agents. Co-administration of stavudine with didanosine is contraindicated due to increased risk of toxicity, including pancreatitis, peripheral neuropathy, and lactic acidosis.
| Serious Effects |
["Hypersensitivity to stavudine or any component of the formulation","Concomitant use with didanosine"]
| Precautions | ["Lactic acidosis/hepatomegaly with steatosis","Pancreatitis (especially with didanosine co-administration)","Peripheral neuropathy","Lipoatrophy/lipodystrophy","Immune reconstitution syndrome","Mitochondrial toxicity (including in infants exposed in utero)","Hepatic decompensation in patients with hepatitis co-infection"] |
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| Fetal Monitoring | Monitor maternal: baseline and periodic serum lactate (risk of lactic acidosis), liver enzymes, amylase, and neurologic symptoms for peripheral neuropathy. Fetal: ultrasound fetal growth and anatomy if used in first trimester (limited data). Monitor neonate for signs of mitochondrial toxicity (hypotonia, seizures, lactic acidosis) if exposed in utero. |
| Fertility Effects | No direct studies on fertility. In animal studies, no impact on mating or fertility at systemic exposures similar to human therapeutic levels. However, stavudine may cause mitochondrial dysfunction in oocytes/sperm, potentially affecting fertility, but clinical significance unknown. |