Didanosine

• Type of Drug: Antiviral
• Prescribed for: HIV infection (AIDS)

General Information

Didanosine is approved for people with AIDS who have been on long-term Zidovudine treatment and whose disease is continuing to worsen. It is also approved for children aged 6 months and older with AIDS who cannot tolerate or respond to Zidovudine.

Didanosine interferes with the reproduction of the HIV virus by interrupting its internal DNA manufacturing process. DNA carries the essential genetic message that directs all life processes, in this case interfering with the life of the HIV virus. Didanosine was tested in patients with advanced AIDS. It was approved because of its ability to prolong life or extend the time until patients developed a new AIDS-related opportunistic infection or another AIDS-defining event. Didanosine also was able to increase blood levels of CD4 cells. CD4 cells are considered important indicators of the severity of an AIDS infection because they represent the level of immune function.

Cautions and Warnings

The most serious (and possibly fatal) side effects of Didanosine are nervous system inflammation and inflammation of the pancreas.

Up to half of patients who take Didanosine experience symptoms of nervous system inflammation and about 1/3 may need to reduce their dosage of Didanosine to control these symptoms. It generally comes in the form of numbness, tingling and pain in the hands and feet. People who already have signs of this kind of nerve damage should not take Didanosine.

Possibly fatal inflammation of the pancreas has developed in up to 3 percent of people taking Didanosine. A third of people with a history of pancreatic inflammation who take Didanosine are likely to develop this problem. Some symptoms of inflammation of the pancreas are major changes in blood sugar levels, rising levels of triglycerides in the blood, a drop in blood calcium, nausea, vomiting or abdominal pain. People who develop pancreas inflammation must stop taking Didanosine.

Liver failure may develop in people taking this medicine. Fifteen to 20 percent of people taking Didanosine will develop abnormal liver function tests and a small number may go on to fatal liver disease.

Four children taking this drug developed severe eye disease, causing some loss of sight. The progress of the eye disease slowed or stopped when dosage was reduced. Children taking this medicine should undergo eye examinations every 6 months or if vision starts to worsen.

Didanosine has caused muscle toxicities in animals. This has not been seen in humans, but can occur with other AIDS antiviral medicines.

Kidney and liver disease can interfere with the elimination of Didanosine from your body. Dosage reduction may be needed to accommodate these situations.

Do not take Didanosine if you are allergic to it or any ingredient in the Didanosine tablet.

Possible Side Effects

• Most common: diarrhea, nervous system inflammation, fever and chills, itching, rash, abdominal pain, weakness, pains, headache, nausea and vomiting, infection, pneumonia, pancreas inflammation.
• Less common: tumors, muscle pain, appetite loss, dry mouth, convulsions, abnormal thought patterns, breathing difficulty, drug allergy, anxiety, nervousness, twitching, confusion, depression and blood component abnormalities.
• Rare: abscesses, skin infections, cysts, dehydration, flu-like symptoms, hernia, heck rigidity, numbness of the hands or feet, chest pain, blood pressure changes, heart palpitations, migraines, dizziness, coldness in the hands or feet, leg pains, colitis, stomach gas, stomach inflammation, ulcers or bleeding, oral fungus infections, personality changes, memory loss, convulsions, dizziness, muscle stiffness, loss of muscle control, poor coordination, loss of bowel control, stroke, feelings of ill health, paranoia, paralysis, psychosis, sleep disturbances, speech difficulties, tremors, joint inflammation or pains, swelling in the legs or arms, asthma, bronchitis, cough, nosebleeds, laryngitis, pneumonia, respiratory difficulties, blurred vision, double vision, conjunctivitis, dry eyes, hearing abnormalities, glaucoma, herpes infections of the skin, sweating.

Almost all children who take Didanosine experience drug side effects. They are likely to experience many of the same reactions as adults but most commonly develop chills, fever, weakness, appetite loss, nausea and vomiting, diarrhea, liver dysfunction, pains, headache, nervousness, sleeplessness/cough, runny nose, asthma or difficulty breathing, rashes, skin problems, and feelings of ill health.

Drug Interactions

• Other drugs that can cause inflammation of the nervous system such as Chloramphenicol, Cisplatin, Dapsone, Disulfiram, Ethionamide, Glutethimide, Gold, Hydralazine, Isoniazid, Metronidazole, Nitrofurantoin, Ribavirin, and Vincristine should be avoided while you are taking Didanosine.
• Didanosine should not be taken together with Zalcitabine.
• Drugs that can cause inflammation of the pancreas (including intravenous Pentamidine) should not be taken with Didanosine.
• Quinolone anti-infectives, tetracycline antibiotics and other drugs whose absorption into the bloodstream can be affected by antacids should not be taken within 2 hours of Didanosine because of its high magnesium and aluminum content.

Food Interactions

Food can prevent the absorption of up to ½ of a dose of Didanosine. Take Didanosine on an empty stomach.

Usual Dose

Adult: 167 to 250 mg every 12 hours.
Child: 50 to 250 mg per day.
Drug dosage should be adjusted to the patient’s level of kidney and liver function.

Overdosage

Didanosine overdose causes many of the drug’s usual side effects, especially inflammation of the nervous system or pancreas, diarrhea and liver failure. There is little experience with Didanosine overdose and victims should be taken to a hospital emergency room for testing and monitoring. ALWAYS remember to bring the prescription bottle with you.

Special Information

Didanosine is not an AIDS cure, nor will it prevent you from transmitting the HIV virus to another person. Patients may still develop AIDS-related opportunistic infections while taking this medicine.
Didanosine can affect components of the blood system. Your doctor will perform blood tests to check for any changes.

People taking Didanosine should take care of their teeth and gums to minimize the possibility of oral infections.

Call your doctor if you develop any of the following symptoms of Didanosine drug toxicity: numbness and pain in the hands and feet, nausea, vomiting or abdominal pain.

If you forget to take a dose of Didanosine, take it as soon as you remember. If it is almost time for your next dose, space the missed dose and your next dose by 4 to 8 hours, then continue your regular schedule. Call your doctor for more specific advice if you forget to take several doses.

How to Take Didanosine

Chewable Tablets: Thoroughly chew the tablets or completely dissolve them in about ¼ cup of water. Drink the entire mixture immediately. Don’t mix with juice or any other acidic drink.

Powder for Solution: Pour the entire contents of a packet into ½ cup of water, stir until dissolved, and drink immediately. Don’t mix with fruit juice or another acidic drink. For children, your pharmacist will prepare a mixture consisting of 10 mg per milliliter of Didanosine and an equal amount of Mylanta Double Strength Antacid or Maalox TC Antacid. This mixture must be stored in a refrigerator and can be kept for 30 days. Shake well before using.

Spilled Didanosine should be cleaned immediately to prevent accidental poisoning.

Special Populations

Pregnancy/Breast-feeding
Didanosine was slightly toxic to pregnant animals receiving doses 12 times human levels. There are no studies of pregnant women taking this medication; however, women who are, or might become, pregnant should only take Didanosine if absolutely necessary and should use effective contraception to avoid passing on the virus.
It is not known if Didanosine passes into breast milk. HIV- infected women who must take this medication should not nurse their infants, but use another method of feeding.

Seniors
People with reduced kidney or liver function, including older adults, should receive smaller doses of Didanosine than those with normal functioning.