didanosine; dideoxyinosine (Videx, ddI)
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Introduction
Tradename: Videx.
Indications
treatment of HIV infection
Dosage
(administration)
- take on an empty stomach
- tablets should be thoroughly chewed, manually crushed or dispersed in at least 1 oz of water
- adult > 60 kg: 200 mg PO BID
- adult < 60 kg: 125 mg PO BID
Videx EC (enteric coated), swallowed whole, not chewed
Tabs: 25, 50, 100, 150 mg.
Powder: 100, 167, 250, 375 mg.
Dosage adjustment in renal failure
Table
| creatinine clearance | dosage |
|---|---|
| > 50-90 mL/min | 12 hour dosing |
| 10-50 mL/min | 24 hour dosing |
| < 10 mL/min* | 50% of dose every 24 hours |
* dose after hemodialysis
Pharmacokinetics
- degraded at acidic pH (food reduces absorption by 50%)
- elimination 1/2life is 1.6 hours (4.5 hours ESRD)
- 50% renally cleared
- patients with creatinine clearance < 60 mL/min may be at greater risk of toxicity
elimination via liver
elimination via kidney
Adverse effects
- common (> 10%)
- peripheral neuropathy
- dose-dependent
- painful
- predominantly distal, symmetric sensory polyneuropathy
- pancreatitis
- headache
- anxiety
- irritability
- insomnia
- restlessness
- abdominal pain
- nausea
- diarrhea
- peripheral neuropathy
- uncommon (< 1%)
- other[2]
- rash
- chills
- syndrome of hepatic steatosis & lactic acidosis[5]
- increased risk of heart attack[7]
- non-cirrhotic portal hypertension [8]
Drug interactions
- increased risk of pancreatitis in combination with:
- separate administration of ddI by at least 2 hours from:
- fluoroquinolones
- tetracyclines
- H2 blockers
- dapsone
- ketoconazole (inactivated by ddI)
- zalcitabine (ddC) SHOULD NOT BE USED in combination; increased risk of neurotoxicity
Laboratory
Mechanism of action
- synthetic purine nucleoside analog of deoxyadenosine
- converted to 5'triphosphate (active anti-viral metabolite) by cellular enzymes
- inhibits replication of HIV by competitively inhibiting HIV reverse transcriptase
More general terms
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ 2.0 2.1 Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ 5.0 5.1 Journal Watch 20(17):137, 2000 Miller et al Ann Intern Med 133:192, 2000
- ↑ Sanford Guide to antimicrobial therapy 2001
- ↑ 7.0 7.1 FDA MedWatch (link for both abacavir & didanosine) http://www.fda.gov/medwatch/safety/2008/safety08.htm#abacavir
- ↑ 8.0 8.1 FDA MedWatch Videx/Videx EC (didanosine): Labeling Revision - Risk of Non-Cirrhotic Portal Hypertension http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm199343.htm