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Didanosine Dosage

Applies to the following strength(s): 100 mg ; 167 mg ; 250 mg ; 50 mg ; 150 mg ; 25 mg ; 10 mg/mL ; 200 mg ; 125 mg ; 400 mg

The information at Drugs.com is not a substitute for medical advice. Always consult your doctor or pharmacist.

Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for HIV Infection

Delayed-release capsules:
Less than 60 kg: 250 mg orally once a day
60 kg or more: 400 mg orally once a day

Oral solution:
Preferred dosing:
Less than 60 kg: 125 mg orally twice a day
60 kg or more: 200 mg orally twice a day

For patients requiring once-daily dosing:
Less than 60 kg: 250 mg orally once a day
60 kg or more: 400 mg orally once a day

Usual Adult Dose for Nonoccupational Exposure

(Not approved by FDA)

Centers for Disease Control and Prevention recommendations:
Delayed-release capsules:
Less than 60 kg: 250 mg orally once a day
60 kg or more: 400 mg orally once a day

Oral solution:
Preferred dosing:
Less than 60 kg: 125 mg orally twice a day
60 kg or more: 200 mg orally twice a day

For patients requiring once-daily dosing:
Less than 60 kg: 250 mg orally once a day
60 kg or more: 400 mg orally once a day

Duration: 28 days

Prophylaxis should be initiated as soon as possible, within 72 hours of exposure. In general, the alternative regimens recommended for nonoccupational postexposure HIV prophylaxis include didanosine as part of protease inhibitor (PI)-based regimens.

Usual Pediatric Dose for HIV Infection

Delayed-release capsules:
20 to less than 25 kg: 200 mg orally once a day
25 to less than 60 kg: 250 mg orally once a day
60 kg or more: 400 mg orally once a day

Oral solution:
2 weeks to 8 months: 100 mg/m2 orally twice a day
9 months to 18 years: 120 mg/m2 orally twice a day; adult dose should not be exceeded

Renal Dose Adjustments

Adults:
Delayed-release capsules:
CrCl 30 to 59 mL/min:
Less than 60 kg: 125 mg orally once a day
60 kg or more: 200 mg orally once a day

CrCl 10 to 29 mL/min:
Less than 60 kg: 125 mg orally once a day
60 kg or more: 125 mg orally once a day

CrCl 9 mL/min or less:
Less than 60 kg: Not recommended.
60 kg or more: 125 mg orally once a day

Oral solution:
CrCl 30 to 59 mL/min:
Less than 60 kg: 150 mg orally once a day or 75 mg orally twice a day
60 kg or more: 200 mg orally once a day or 100 mg orally twice a day

CrCl 10 to 29 mL/min:
Less than 60 kg: 100 mg orally once a day
60 kg or more: 150 mg orally once a day

CrCl 9 mL/min or less:
Less than 60 kg: 75 mg orally once a day
60 kg or more: 100 mg orally once a day

Children: There are insufficient data to recommend doses in renal insufficiency. The manufacturer recommends a dose reduction and/or increase in interval.

Liver Dose Adjustments

No adjustment recommended.

Dose Adjustments

Adults:
Concomitant tenofovir (CrCl 60 mL/min or more):
Delayed-release capsules or oral solution:
Less than 60 kg: 200 mg orally once a day
60 kg or more: 250 mg orally once a day

The delayed-release capsules should be taken together with tenofovir and a light meal (400 kilocalories or less, 20% fat or less) or in the fasted state. The oral solution and tenofovir may be taken together in the fasted state. Alternatively, if tenofovir is taken with food, the oral solution should be taken on an empty stomach.

Precautions

Concomitant use of didanosine and allopurinol is contraindicated due to increased systemic exposures of didanosine. Concomitant use of didanosine and ribavirin is contraindicated due to increased exposures of the active metabolite of didanosine.

Fatal and nonfatal pancreatitis has occurred during therapy with didanosine used alone or in combination regimens. Didanosine should be suspended in patients with signs or symptoms of pancreatitis and discontinued if pancreatitis is confirmed. Coadministration of didanosine with drugs that are known to cause pancreatitis may increase the risk of this toxicity. Didanosine should be suspended if treatment with life-sustaining drugs known to cause pancreatitis is required.

Didanosine should be used with extreme caution and only if clearly indicated in patients with risk factors for pancreatitis. Patients with advanced HIV-1, especially elderly patients, are at increased risk of pancreatitis and should be monitored closely. Patients with renal dysfunction may be at increased risk if treated without dose adjustment. The frequency of pancreatitis is dose related.

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with other antiretroviral agents. Risk factors for lactic acidosis may include female gender, obesity, and prolonged nucleoside exposure. Caution is recommended in patients with risk factors for liver disease; however, cases have been reported in patients with no known risk factors. Fatal lactic acidosis has been reported in pregnant women who received the combination of didanosine and stavudine with other antiretroviral agents. The combination of didanosine and stavudine should be used with caution during pregnancy and only if there are no other alternatives. Treatment should be suspended in any patient that develops findings suggestive of pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations), symptomatic hyperlactatemia, or lactic acidosis.

It is unknown if hepatic impairment significantly affects didanosine pharmacokinetics. Patients should be monitored closely for evidence of didanosine toxicity. The safety and efficacy of didanosine have not been established in HIV-infected patients with significant underlying liver disease. During combination antiretroviral therapy, patients with preexisting liver dysfunction have an increased frequency of liver function abnormalities, including severe and potentially fatal hepatic adverse events, and should be monitored according to standard practice. If there is evidence of worsening liver disease in such patients, interruption or discontinuation of treatment must be considered.

Fatal hepatic events were reported most frequently in patients receiving didanosine with stavudine and hydroxyurea; therefore, this combination should be avoided.

Noncirrhotic portal hypertension, including cases leading to liver transplantation or death, has been reported during postmarketing experience. Cases of didanosine-associated noncirrhotic portal hypertension were confirmed by biopsy and had no alternative etiology for the diagnosis. Onset of signs and symptoms (including elevated liver enzymes, esophageal varices, hematemesis, ascites, and splenomegaly) ranged from months to years following didanosine initiation. During routine medical visits, patients receiving didanosine should be monitored for early signs of portal hypertension (e.g., thrombocytopenia and splenomegaly). Appropriate laboratory testing including liver enzymes, serum bilirubin, albumin, complete blood count, international normalized ratio, and ultrasonography should be considered. Didanosine should be discontinued in patients with evidence of noncirrhotic portal hypertension.

Peripheral neuropathy has been reported. It has occurred more often in patients with advanced HIV disease, with a history of neuropathy, or being treated with neurotoxic drugs, including stavudine. Didanosine discontinuation should be considered in patients developing peripheral neuropathy.

Retinal changes and optic neuritis have been reported in patients taking didanosine. Periodic retinal examinations may be advisable.

Immune reconstitution syndrome has occurred during combination antiretroviral therapy. Patients responding to therapy may develop an inflammatory response to indolent or residual opportunistic infections and require evaluation and treatment.

The potential for HIV cross-resistance among nucleoside reverse transcriptase inhibitors exists but has not been fully explored. It is unknown what effect didanosine therapy will have on the activity of subsequently administered nucleoside reverse transcriptase inhibitors. Selection of antiretroviral agents for a patient's medication regimen should be done carefully and in consultation with an infectious disease expert.

Safety and efficacy of didanosine have not been established in pediatric patients less than 2 weeks of age. Safety and efficacy of didanosine delayed-release capsules have not been established in pediatric patients less than 20 kg.

Dialysis

Adults:
Hemodialysis or CAPD:
Delayed-release capsules:
Less than 60 kg: Not recommended.
60 kg or more: 125 mg orally once a day

Oral solution:
Less than 60 kg: 75 mg orally once a day
60 kg or more: 100 mg orally once a day

Supplemental doses after hemodialysis are not required.

Other Comments

Didanosine should be administered at least 30 minutes before or 2 hours after a meal.

If a patient is unable to reliably swallow a didanosine capsule, then the oral solution should be used.

Delayed-release capsules: The capsules should be swallowed whole. They should not be chewed, crushed, or opened.

Pediatric powder for solution: The reconstituted pediatric oral solution should be stored in the refrigerator and shaken well before each use. Any unused portion should be discarded after 30 days.

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