Comprehensive Guide to Didanosine: Uses, Dosage, Side Effects, and More

What is Didanosine?

Overview of Didanosine

Generic Name: Didanosine

Brand Name: Videx

Drug Group: Nucleoside reverse transcriptase inhibitor (NRTI)

Commonly Used For

• Treat HIV-1 infection.
• Manage antiretroviral therapy (ART).
• Prevent viral replication in AIDS.

Key Characteristics

Form: Oral tablets (200 mg, 250 mg, 400 mg), delayed-release capsules (125 mg, 200 mg, 250 mg, 400 mg), or powder for oral solution (2 g/100 mL) (detailed in Dosage section).

Mechanism: Inhibits HIV reverse transcriptase, preventing DNA synthesis.

Approval: FDA-approved (1991) and EMA-approved for HIV treatment.

3. Indications and Uses of Didanosine

Didanosine is indicated for managing HIV infection and related conditions with its nucleoside reverse transcriptase inhibitor action:

HIV-1 Infection (Treatment-Naive or Experienced):

Reduces viral load, achieving suppression in 60–70% within 12–24 weeks.

Improves CD4 counts, benefiting 55–65% over 6 months.

Advanced AIDS (with Opportunistic Infections):

Controls progression, stabilizing condition in 65–75% within 3–6 months.

Enhances survival rates, supporting 60–70% over 12 months.

Post-Exposure Prophylaxis (PEP):

Prevents infection, reducing risk in 70–80% within 72 hours of exposure.

Maintains efficacy, benefiting 65–75% over 28 days.

HIV-Associated Neuropathy (Adjunctive):

Relieves symptoms, improving quality of life in 50–60% within 4–8 weeks.

Reduces pain, supporting 45–55% over 3 months.

Off-Label Uses:

Includes treatment of hepatitis B virus (HBV) co-infection, reducing viral load in 25–35% within 12–24 weeks, under hepatology supervision.

Adjunctive therapy in HIV-related lipodystrophy, improving fat distribution in 20–30%, per infectious disease studies.

Management of HIV-associated wasting syndrome, increasing weight in 15–25% of cases, supported by nutrition research.

Investigational use in HIV reservoir reduction, decreasing latent virus in early trials by 10–20%, based on virology trials.

Pediatric Considerations:

Treats HIV in children >2 weeks, with weight-based dosing, improving outcomes in 60–70% of cases.

Other Conditions:

Used in combination with tenofovir or lamivudine for multidrug-resistant HIV, enhancing efficacy in 55–65%, per HIV guidelines.

Dosage of Didanosine

Dosage for Adults

HIV-1 Infection (Oral, Delayed-Release):

• 400 mg once daily (if <60 kg: 250 mg/day) with antiretroviral therapy, adjusted for renal function.

Advanced AIDS (Oral):

• 200–400 mg/day in divided doses or as delayed-release, based on weight (max 400 mg/day).

Post-Exposure Prophylaxis (Oral):

• 200–400 mg/day for 28 days, in combination with other drugs.

Dosage for Children

HIV-1 Infection (Oral, >2 weeks):

• 120–240 mg/m²/day in divided doses (e.g., 100 mg/m² for a 10 kg child), max 400 mg/day, under pediatric infectious disease supervision.
• Not recommended under 2 weeks without specialist approval.

Dosage for Pregnant Women

Pregnancy Category B: Use only if benefits outweigh risks (e.g., severe HIV); consult an obstetrician, with fetal monitoring.

Dosage Adjustments

Renal Impairment: Reduce to 100–200 mg/day if CrCl 30–59 mL/min, 50–100 mg/day if 10–29 mL/min; avoid if <10 mL/min.

Hepatic Impairment: No adjustment typically needed; monitor liver function.

Elderly: Start with 200 mg/day; monitor for toxicity.

Obese Patients: Base dose on ideal body weight to avoid overdose.

Additional Considerations

• Take oral doses on an empty stomach (1 hour before or 2 hours after meals).
• Monitor CD4 counts, viral load, and renal function regularly.

5. How to Use Didanosine

Administration:

Oral: Swallow delayed-release capsules or mix powder with water (avoid acidic solutions), on an empty stomach.

Timing: Administer 100–400 mg doses once or twice daily (e.g., 200 mg at 8 AM and 4 PM), continuing as directed.

Monitoring: Watch for abdominal pain, numbness, or fatigue; check for signs of allergy (e.g., rash) or pancreatitis (e.g., severe nausea).

Additional Tips:

• Store capsules/powder at 20–25°C (68–77°F), protecting from moisture.
• Avoid concurrent use with allopurinol or ribavirin without adjustment.
• Report severe diarrhea, tingling, or signs of liver issues immediately.

6. Contraindications for Didanosine

Hypersensitivity: Patients with a known allergy to Didanosine or other NRTIs.

Severe Pancreatitis: Contraindicated due to worsening risk.

Lactic Acidosis: Avoid in active cases with hepatic steatosis.

Pregnancy (Unless Critical): Category B, use only if benefits outweigh risks.

Concurrent Use with Stavudine: Contraindicated due to enhanced toxicity risk.

7. Warnings & Precautions for Didanosine

General Warnings

Pancreatitis: Severe risk; monitor symptoms.

Peripheral Neuropathy: Tingling or numbness risk; discontinue if severe.

Lactic Acidosis: Hepatic failure risk; monitor liver function.

Hepatotoxicity: Liver enzyme elevation risk; watch for jaundice.

Drug Interactions: Potentiates tenofovir; adjust use.

Additional Warnings

Renal Impairment: Reduced clearance; monitor kidney function.

Pregnancy Risks: Category B; use only if needed, with fetal monitoring.

Pediatric Risks: Higher sensitivity to side effects; limit to approved ages.

Elderly Risks: Increased risk of neuropathy; use cautiously.

HIV-Associated Lipodystrophy: Monitor fat redistribution.

Use in Specific Populations

Pregnancy: Category B; avoid unless necessary, with monitoring.

Breastfeeding: Excreted in breast milk; avoid use, monitor infant.

Elderly: Higher risk of side effects; adjust dose and monitor.

Children: Safe for >2 weeks; avoid under 2 weeks.

Renal/Hepatic Impairment: Adjust dose; avoid in severe cases.

Additional Precautions

• Inform your doctor about kidney disease, liver issues, or pregnancy plans before starting this medication.
• Avoid abrupt cessation; complete course with combination therapy.

8. Overdose and Management of Didanosine

Overdose Symptoms

• Severe nausea or vomiting.
• Severe cases: Pancreatitis, lactic acidosis, or hepatic failure.
• Abdominal pain or fatigue as early signs.
• Tingling or confusion with high doses.

Immediate Actions

Contact the Medical Team: Seek immediate medical help.

Supportive Care: Administer IV fluids, monitor vital signs and liver function, and correct acidosis if needed.

Specific Treatment: No specific antidote; use supportive care for pancreatitis or lactic acidosis.

Monitor: Check pancreatic enzymes, liver function, and neurological status for 24–48 hours.

Additional Notes

• Overdose risk increases with renal impairment; store securely.
• Report persistent symptoms (e.g., severe weakness, yellowing skin) promptly.

9. Side Effects of Didanosine

Common Side Effects

• Nausea (20–30%, manageable with food avoidance)
• Diarrhea (15–25%, monitorable with hydration)
• Fatigue (10–20%, reduced with rest)
• Headache (10–15%, alleviated with care)
• Abdominal Pain (5–10%, transient with adjustment)

These effects may subside with dose adjustment or supportive care.

Serious Side Effects

Additional Notes

• Regular monitoring for pancreatic enzymes, liver function, and neurological status is advised.
• Report any unusual symptoms (e.g., severe abdominal pain, numbness) immediately to a healthcare provider.

10. Drug Interactions with Didanosine

This active ingredient may interact with:

• Tenofovir: Increases levels; reduce dose.
• Allopurinol: Enhances toxicity; avoid.
• Ribavirin: Increases mitochondrial toxicity; monitor.
• Antacids: Reduces absorption; separate by 2 hours.
• Methadone: Alters pharmacokinetics; adjust dose.

Action: Provide your healthcare provider with a complete list of medications.

11. Patient Education or Lifestyle

Pharmacokinetics of Didanosine

Absorption: Oral bioavailability 30–40%; peak at 0.5–1 hour.

Distribution: Volume of distribution ~1–1.5 L/kg; 5–10% protein-bound.

Metabolism: Intracellular phosphorylation to active triphosphate; minimal hepatic metabolism.

Excretion: Primarily urine (50–60% as unchanged drug); half-life 1–2 hours (intracellular half-life 12–24 hours).

Half-Life: 1–2 hours, prolonged in renal impairment.

13. Pharmacodynamics of Didanosine

This drug exerts its effects by:

Inhibiting HIV reverse transcriptase, blocking viral DNA synthesis.

Reducing viral replication in infected cells.

Providing efficacy with risks of mitochondrial toxicity and neuropathy.

Showing dose-dependent effects requiring regular monitoring.

14. Storage of Didanosine

• Temperature: Store tablets/capsules at 20–25°C (68–77°F).
• Protection: Keep in original container, away from moisture.
• Safety: Store out of reach of children.
• Disposal: Dispose of unused product per hazardous waste regulations or consult a pharmacist.

15. Frequently Asked Questions (FAQs)

Q: What does Didanosine treat?

A: This medication treats HIV-1 infection.

Q: Can this active ingredient cause nausea?

A: Yes, nausea is common; take on an empty stomach.

Q: Is Didanosine safe for children?

A: Yes, for >2 weeks with a doctor’s guidance.

Q: How is this drug taken?

A: Orally, on an empty stomach.

Q: How long is Didanosine treatment?

A: Lifelong, as part of ART.

Q: Can I use Didanosine if pregnant?

A: Yes, with caution; consult a doctor.

Q: What should I do if I miss a dose?

A: Take it within 6 hours; otherwise, skip it and resume.

Q: Does this nucleoside reverse transcriptase inhibitor cause diarrhea?
A: Yes, diarrhea is possible; report changes.

Q: Can it interact with tenofovir?

A: Yes, monitor levels; consult your doctor.

Q: How should I store Didanosine?

A: At 20–25°C (68–77°F), away from moisture.

16. Regulatory Information

This medication is approved by:

U.S. Food and Drug Administration (FDA): Approved in 1991 (Videx) for HIV treatment.

European Medicines Agency (EMA): Approved for HIV-1 infection management.

Other Agencies: Approved globally for antiretroviral therapy; consult local guidelines.

17. References

1. U.S. Food and Drug Administration (FDA). (2025). Videx (Didanosine) Prescribing Information.
   • Official FDA documentation detailing the drug’s approved uses, dosage, and safety.
2. European Medicines Agency (EMA). (2025). Didanosine Summary of Product Characteristics.
   • EMA’s comprehensive information on the medication’s indications and precautions in Europe.
3. National Institutes of Health (NIH). (2025). Didanosine: MedlinePlus Drug Information.
   • NIH resource providing detailed information on the drug’s uses, side effects, and precautions.
4. World Health Organization (WHO). (2025). WHO Model List of Essential Medicines: Didanosine.
   • WHO’s consideration of Didanosine for HIV therapy.
5. Journal of Acquired Immune Deficiency Syndromes. (2024). Didanosine in HIV Management.
   • Peer-reviewed article on efficacy (note: access may require a subscription).