STAVUDINE; LAMIVUDINE; EFAVIRENZ
Clinical safety rating: safe
Other drugs that cause peripheral neuropathy or pancreatitis increase risk Can cause peripheral neuropathy and pancreatitis.
Combination antiretroviral: stavudine is a nucleoside reverse transcriptase inhibitor (NRTI); lamivudine is an NRTI; efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI). Stavudine and lamivudine are phosphorylated intracellularly to active triphosphate metabolites that compete with natural substrates and incorporate into viral DNA, causing chain termination. Efavirenz binds directly to reverse transcriptase, causing allosteric inhibition and preventing RNA-dependent DNA polymerization.
| Metabolism | Stavudine: not significantly metabolized, excreted unchanged in urine. Lamivudine: not significantly metabolized, excreted unchanged in urine. Efavirenz: primarily metabolized by CYP2B6 and CYP3A4 to inactive metabolites. |
| Excretion | Stavudine: 40% renal (unchanged), 60% biliary/fecal (metabolites). Lamivudine: 70% renal (unchanged), 30% fecal (metabolites). Efavirenz: 16-61% renal (metabolites), 14-34% fecal (unchanged). |
| Half-life | Stavudine: 1.0-1.6 h (adults), 2.5-5.0 h (neonates). Lamivudine: 5-7 h (adults), 10-14 h (neonates). Efavirenz: 40-55 h (single dose), 52-76 h (multiple doses). |
| Protein binding | Stavudine: negligible (<5%). Lamivudine: <36% (albumin). Efavirenz: 99.5-99.8% (albumin). |
| Volume of Distribution | Stavudine: 0.5-0.6 L/kg (total body water). Lamivudine: 1.3-1.5 L/kg (extensively distributed). Efavirenz: 2.4-4.0 L/kg (large, extensive tissue binding). |
| Bioavailability | Oral: Stavudine: 86% (fasting). Lamivudine: 86-88% (fasting). Efavirenz: 40-45% (fasting; increased with high-fat meal). |
| Onset of Action | Oral: Stavudine: 0.5-1 h (peak plasma). Lamivudine: 0.5-1.5 h (peak plasma). Efavirenz: 3-5 h (peak plasma). Clinical antiviral effect: days to weeks. |
| Duration of Action | 12 h (stavudine/lamivudine, due to dosing interval), 24 h (efavirenz, due to long half-life). Clinical suppression: continuous with adherence. |
One tablet (stavudine 30 mg + lamivudine 150 mg + efavirenz 600 mg) orally once daily on an empty stomach, preferably at bedtime.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-50 mL/min: reduce lamivudine dose to 150 mg once daily (use separate components). CrCl <30 mL/min or hemodialysis: not recommended. Stavudine: CrCl 26-50 mL/min: 15 mg every 12h; CrCl 10-25 mL/min: 15 mg every 24h; CrCl <10 mL/min: 15 mg every 24h. Efavirenz: no renal adjustment. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: contraindicated due to efavirenz. Child-Pugh Class C: contraindicated. |
| Pediatric use | Stavudine: based on body weight: <30 kg 1 mg/kg every 12h; 30-60 kg 30 mg every 12h; >60 kg 40 mg every 12h. Lamivudine: 4 mg/kg twice daily (max 150 mg twice daily) for children ≥3 months. Efavirenz: for children ≥3 years and ≥10 kg: based on weight: 10-15 kg: 200 mg once daily; 15-20 kg: 250 mg once daily; 20-25 kg: 300 mg once daily; 25-32.5 kg: 350 mg once daily; 32.5-40 kg: 400 mg once daily; ≥40 kg: 600 mg once daily. |
| Geriatric use | No specific dose adjustment; monitor renal function and consider age-related decline in creatinine clearance; use with caution due to increased risk of neuropsychiatric effects from efavirenz. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that cause peripheral neuropathy or pancreatitis increase risk Can cause peripheral neuropathy and pancreatitis.
| FDA category | Animal |
| Breastfeeding | All three drugs are excreted into human breast milk. The M/P ratios: lamivudine approximately 3.3, stavudine approximately 1.0, efavirenz approximately 1.0. Breastfeeding is not recommended in HIV-infected mothers due to risk of HIV transmission, regardless of antiretroviral therapy. If a mother is on this regimen for other reasons (rare), she should be advised against breastfeeding. |
| Teratogenic Risk |
■ 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. Fatal pancreatitis has occurred with stavudine. Hepatotoxicity, including hepatic failure and death, has been reported with efavirenz.
| Common Effects | Peripheral neuropathy |
| Serious Effects |
["Hypersensitivity to any component","Concomitant use with voriconazole (efavirenz decreases voriconazole levels; alternative therapy recommended)","Efavirenz should not be used in patients with moderate to severe hepatic impairment (Child-Pugh class B or C)"]
| Precautions | ["Lactic acidosis/severe hepatomegaly with steatosis (discontinue if suspected)","Pancreatitis (discontinue if signs/symptoms occur)","Hepatotoxicity with efavirenz (monitor liver enzymes)","Lipodystrophy and metabolic abnormalities","Immune reconstitution syndrome","Fat redistribution (stavudine use)","Peripheral neuropathy (stavudine dose-related)","Psychiatric symptoms (efavirenz: dizziness, insomnia, depression, suicide risk)","Skin rash (efavirenz: severe reactions including Stevens-Johnson syndrome)","Hyperlipidemia (efavirenz)","Drug interactions (efavirenz induces and inhibits CYP enzymes)","Redistribution/accumulation of body fat (associated with NRTIs)"] |
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| This combination contains efavirenz, which is classified as FDA Pregnancy Category D. First trimester exposure is associated with an increased risk of neural tube defects (approximately 0.2% incidence) and other congenital anomalies. For second and third trimesters, continued use is considered if benefit outweighs risk, but monitoring for hepatotoxicity and mitochondrial toxicity in the neonate is advised. |
| Fetal Monitoring | Maternal: Regular liver function tests (especially with efavirenz), complete blood count, and HIV viral load monitoring. Fetal: Ultrasound at 18-20 weeks to assess for neural tube defects if first trimester efavirenz exposure; neonatal monitoring for anemia, hyperbilirubinemia, and mitochondrial toxicity. |
| Fertility Effects | Efavirenz has been associated with potential reductions in progesterone levels and possible luteal phase defects, which may affect fertility. Stavudine and lamivudine have not shown significant effects on fertility in animal studies. Overall impact is minimal but may contribute to subfertility in some women. |