Didanosine
VIDEX
Pronunciation: dye-DAN-oe-seen (VYE-dex)
What it isA dideoxynucleoside reverse transcriptase inhibitor (NRTI) that, after intracellular phosphorylation, terminates HIV proviral DNA chain elongation.
Why this oneAn older, now rarely used HIV agent historically valued as a thymidine-sparing backbone option.
What limits itIt causes dose-related peripheral neuropathy and pancreatitis, requires acid buffering or enteric coating, and its toxicity is amplified by tenofovir, allopurinol, and ribavirin.
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| HIV-1 infection (combination antiretroviral therapy) | Adults (weight-based) | >=60 kg: 400 mg QD; 25-<60 kg: 250 mg QD; 20-<25 kg: 200 mg QD | Same (fixed weight-based dose) | 400 mg QD |
| HIV-1 infection (combination antiretroviral therapy) | Peds 6-18 y, >=20 kg, able to swallow capsules | Same weight-based table as adults (200-400 mg QD) | Same | 400 mg QD |
Renal Adults: CrCl 30-59: 200 mg QD (>=60 kg) / 125 mg QD (<60 kg); CrCl 10-29: 125 mg QD; CrCl <10, CAPD or hemodialysis: 125 mg QD (>=60 kg; <60 kg <10 mL/min use pediatric powder); no post-hemodialysis supplement. Peds: consider reduction (insufficient data)
Hepatic No adjustment needed
With tenofovir DF: reduce to 250 mg QD (>=60 kg) or 200 mg QD (<60 kg) taken with tenofovir + light meal or fasted (CrCl >=60 only; not established below)
Instructions
- Take on an empty stomach
- Swallow capsules intact
Available strengths
- DR cap 200, 250, 400 mg
Contraindications
- Coadministration with allopurinol (increases didanosine exposure/toxicity)
- Coadministration with ribavirin (increased ddATP; fatal hepatic failure, peripheral neuropathy, pancreatitis, lactic acidosis reported)
Cautions
- Pancreatitis — dose-related, may be fatal; higher risk with stavudine, renal impairment without dose adjustment, advanced HIV, elderly
- Lactic acidosis/severe hepatomegaly with steatosis; suspend for symptoms
- Hepatic toxicity; avoid hydroxyurea + didanosine + stavudine (fatal hepatic events)
- Non-cirrhotic portal hypertension (incl. cases needing transplant/fatal) — discontinue if evident
- Peripheral neuropathy
- Retinal changes and optic neuritis
- Immune reconstitution syndrome; fat redistribution
Adverse reactions
- Diarrhea
- Peripheral neuropathy/neurologic symptoms
- Nausea
- Headache
- Rash
- Vomiting
Pregnancy Category B; use only if benefit justifies risk — fatal lactic acidosis reported with didanosine + stavudine in pregnancy (use that combo only if clearly needed); pregnancy registry 1-800-258-4263
Lactation Do not breastfeed (HIV transmission risk + potential infant toxicity; excreted in rat milk)
Cost
| Strength | #/mo | generic $/mo | CostPlus | |
|---|---|---|---|---|
| 200 mg | DR cap | 30 qd | not offered | |
| 250 mg | DR cap | 30 qd | not offered | |
| 400 mg | DR cap | 30 qd | not offered |
⚠ BOXED WARNINGS
- Pancreatitis
- Lactic acidosis and severe hepatomegaly with steatosis
Principal riskBoxed warning: fatal and nonfatal pancreatitis, and lactic acidosis with severe hepatomegaly and steatosis.