didanosine
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didanosine
[di-dan´o-sēn]didanosine (ddI, 2,3-dideoxyinosine)
Pharmacologic class: Nucleoside reverse transcriptase inhibitor
Therapeutic class: Antiretroviral, antiviral
Pregnancy risk category B
FDA Box Warning
• Pancreatitis has occurred when drug was used alone or in combination regimens in treatment-naive or treatment-experienced patients. Suspend therapy in patients with suspected pancreatitis; discontinue in patients with confirmed pancreatitis.
• Drug may cause lactic acidosis and severe hepatomegaly with steatosis when used alone or in combination with other antiretrovirals. Fatal lactic acidosis has occurred in pregnant women receiving didanosine-stavudine combination with other antiretrovirals. In pregnant patients, use this combination with caution and only if benefit clearly outweighs risk.
Action
Inhibits replication of human immunodeficiency virus (HIV) by disrupting synthesis of DNA polymerase, an enzyme crucial to DNA and RNA formation
Availability
Capsules (delayed-release): 125 mg, 200 mg, 250 mg, 400 mg
Powder for oral solution (pediatric): 2 g in 4-oz glass bottle, 4 g in 8-oz glass bottle
Indications and dosages
➣ HIV infection
Adults weighing 60 kg (132 lb) or more: 400 mg (capsules) P.O. once daily
Adults weighing less than 60 kg (132 lb): 250 mg (capsules) P.O. once daily
Children: 120 mg/m2 (powder for oral solution, pediatric) P.O. q 12 hours
Dosage adjustment
• Renal impairment
Contraindications
• Hypersensitivity to drug
• Concurrent use of allopurinol or ribavirin
Precautions
Use cautiously in:
• renal or hepatic impairment, peripheral neuropathy, hyperuricemia
• elderly patients
• pregnant or breastfeeding patients
• children.
Administration
• Know that drug is usually given in conjunction with other antiretrovirals.
• Give on empty stomach 30 minutes before or 2 hours after a meal.
• Don't administer with fruit juice.
• Know that pharmacist must prepare pediatric powder for oral solution by diluting with water and antacid to a concentration of 10 mg/ml.
• Be aware that delayed-release capsules aren't intended for use in children.
Adverse reactions
CNS: dizziness, anxiety, abnormal thinking, hypoesthesia, agitation, confusion, hypertonia, asthenia, peripheral neuropathy, seizures, coma
CV: peripheral coldness, palpitations, hypotension, bradycardia, weak pulse, pseudoaneurysm, incomplete atrioventricular (AV) block, complete AV block, nodal arrhythmias, ventricular tachycardia, thrombophlebitis, embolism
EENT: diplopia, abnormal vision, ocular hypotony, iritis, retinal detachment
GI: nausea, vomiting, diarrhea, abdominal enlargement, dyspepsia, ileus, GI reflux, hematemesis, dysphagia, dry mouth, pancreatitis
GU: urinary retention, frequency, or incontinence; dysuria; cystalgia; prostatitis; renal dysfunction; nephrotoxicity
Hematologic: anemia, leukocytosis, thrombocytopenia, bleeding, neutropenia
Hepatic: hepatomegaly with steatosis, noncirrhotic portal hypertension
Metabolic: diabetes mellitus, hyperkalemia, lactic acidosis, noncirrhotic portal hypertension
Musculoskeletal: muscle contractions
Respiratory: pneumonia, crackles, rhonchi, bronchitis, pleurisy, dyspnea, wheezing, pleural effusion, pulmonary edema, pulmonary embolism, bronchospasm
Skin: diaphoresis, pallor, rash, urticaria, pruritus, bullous eruption, petechiae, cellulitis, abscess
Other: edema, development of human antichimeric antibodies
Interactions
Drug-drug. Allopurinol, ganciclovir (oral), ribavirin, tenofovir: increased didanosine blood level
Amprenavir, delavirdine, indinavir, ritonavir, saquinavir: altered didanosine pharmacokinetics
Antacids, other drugs that increase gastric pH: increased risk of didanosine toxicity
Co-trimoxazole, pentamidine: increased risk of pancreatic toxicity
Dapsone, fluoroquinolones, ketoconazole: decreased blood levels of these drugs
Itraconazole: decreased itraconazole blood level
Methadone: 50% decrease in didanosine blood level
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, uric acid: increased levels
Granulocytes, hemoglobin, platelets, white blood cells: decreased values
Drug-food. Any food: decreased rate and extent of drug absorption
Patient monitoring
☞ Monitor patient for signs and symptoms of pancreatitis. Withhold drug in patients with signs or symptoms of pancreatitis and discontinue drug in patients with confirmed pancreatitis.
☞ Monitor patient for early signs and symptoms of portal hypertension (thrombocytopenia, splenomegaly). Discontinue drug in patients with evidence of noncirrhotic portal hypertension.
☞ Assess carefully for signs and symptoms of lactic acidosis, such as dizziness, light-headedness, and bradycardia.
• Monitor for signs and symptoms of peripheral neuropathy.
• In patients with renal impairment, watch for drug toxicity and hypermagnesemia (suggested by muscle weakness and confusion).
Patient teaching
• Tell patient to take drug on empty stomach.
• Advise patient using buffered powder to mix it with water, not juice, and to let powder dissolve for several minutes before taking.
☞ Instruct patient to immediately report abdominal pain, nausea, vomiting, tiredness, fast or irregular heartbeats, easy bruising, difficulty breathing, yellowing of skin or eyes, or dark urine.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.