Dosing and uses of Videx, Videx EC (didanosine)
Adult dosage forms and strengths
capsule, extended release
- 125mg
- 200mg
- 250mg
- 400mg
powder for solution
- 2 g
- 4 g
HIV Infection
≤60 kg: Extended-release 250 mg PO qDay; 125 mg PO q12hr
>60 kg: Extended-release 400 mg PO qDay; suspension 200 mg PO q12hr
Dosage modifications
Coadministration with tenofovir
- >60 kg: Decrease didanosine dose to 250 mg/day
- ≤60 kg: Decrease didanosine dose to 200 mg/day
Renal Impairment
>60 kg
- CrCl >60 mL/min: Normal dose
- CrCl 30-59 mL/min: 200 mg PO qDay (extended release/solution) or divided q12hr (solution only)
- CrCl 10-29 mL/min: 125 mg (extended release) or 150 mg (solution) PO qDay
- CrCl <10 mL/min; PD/HD: 125 mg (extended release) or 100 mg (solution) PO qDay
≤60 kg
- CrCl >60 mL/min: Normal dose
- CrCl 30-59 mL/min: Extended release 125 mg PO qDay; solution 150 mg PO qDay or divided q12hr
- CrCl 10-29 mL/min: 125 mg (extended release) or 100 mg (solution) PO qDay
- CrCl <10 mL/min; PD/HD: Solution only: 75 mg PO qDay
Administration
Take on empty stomach
Monitor
Amylase q4-8Weeks; CBC with different, aminotransferases, K+, triglycerides q6-12Weeks
Neurologic evalent q4Weeks
Pediatric dosage forms and strengths
capsule, extended release
- 125mg
- 200mg
- 250mg
- 400mg
powder for solution
- 2 g
- 4 g
HIV Infection
2 weeks to <3 months: 50 mg/m² PO q12hr
3-8 months: 100 mg/m² PO q12hr
>8 months old (oral solution): 120 mg/m² (range 90-150 mg/m²) PO q12hr
Videx EC or generic capsules
- 6-18 years and 20 to <25 kg: 200 mg PO qDay
- 6-18 years and 25 to <60 kg: 250 mg PO qDay
- 6-18 years and >60 kg: As adults; 400 mg PO qDay (oral suspension: 200 mg PO q12hr)
Administration
Oral solution dispensed as 10 mg/mL with antacid as diluent
Take on empty stomach
EC not approved for pediatrics
Monitor
Amylase q4-8Weeks; CBC with different, aminotransferases, K+, triglycerides q6-12Weeks
Neurologic evalent q4Weeks
Periodic retinal exams
Videx, Videx EC (didanosine) adverse (side) effects
>10%
Diarrhea (19-28%)
Peripheral neuropathy (17-20%)
Increased amylase (15-17%)
Abdominal pain (7-13%)
1-10%
Increased LFt
Increased uric acid
Pancreatitis (patients >65 years had higher frequency of pancreatitis than younger patients)
Pruritus
Rash
Postmarking Reports
Noncirrhotic portal hypertension
Warnings
Black box warnings
Fatal and nonfatal pancreatitis reported; suspend if pancreatitis suspected and discontinue if confirmed
Lactic acidosis and severe hepatomegaly with steatosis (including fatal cases) reported with use of nucleoside analogues alone or in combination
Fatal lactic acidosis reported in pregnant women who have received didanosine and stavudine with other antiretroviral agents. Use the combination with caution in pregnant women
Contraindications
Hypersensitivity
Coadministration with allopurinol (may increase didanosine toxicity)
Coadministration with ribavirin (increases actrive metabolite dideoxyadenosine 5’-triphosphate levels, causing fatal hepatic failure, peripheral neuropathy, pancreatitis, and symptomatic hyperlactatemia/lactic acidosis)
Cautions
(All NRTIs): Risk of potentially fatal lactic acidosis & severe hepatomegaly with steatosis when used alone or in combination with other antiretrovirals
Risk of potentially fatal pancreatitis, increases if used in combo with stavudine
Risk of potentially fatal bleeding from esophageal varices in patients with non-cirrhotic portal hypertension
Discontinue if pancreatitis occurs; reduce dose for other ADR's
Risk of immune reconstitution syndrome if used in combination w/ other antiretroviral drugs
Risk of retinal changes and optic neuritis
Rapidly degrades in acidic pH, however, EC is protected from stomach acids
Noncirrhotic portal hypertension reported; discontinue if signs/symptoms occur (eg, elevated liver enzymes, esophageal varices, hematemesis, ascites, splenomegaly)
Coadministration of methadone with Videx pediatric powder may significant decrease didanosine concentrations
Pregnancy and lactation
Pregnancy category: B
Lactation: Not known whether distributed into milk. Because of both the potential for HIV transmission and the potential for serious adverse reactions in nursing infants, mothers should be instructed not to breastfeed.
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Videx, Videx EC (didanosine)
Mechanism of action
Nucleoside Reverse Transcriptase Inhibitor (NRTI)
Inhibits in vitro replication of HIV via chain termination & interference with HIV-RNA dependent DNA polymerase
Pharmacokinetics
Bioavailability: 42% (adults); 25% (children)
Protein Bound: <5%
Metabolism: Liver
Excretion: Urine
Vd: 28 L/m² (children); 1.08 L/kg
Half-life elimination: 0.8 hr (children and adolescents); 1.5 hr (adults)
