Potential side effects and toxicity: Peripheral neuropathy (tingling, burning, numbness or pain in the hands or feet) may go away once didanosine is stopped, but can be painful and permanently debilitating if not treated in time and occurs more frequently when used with Zerit. Upset stomach, diarrhea, headache, and more rarely pancreatitis has also been reported. Other toxicities include eye changes and optic neuritis. Have periodic eye exam by someone who is aware you are HIV-positive. Increased uric acid levels (indicating a number of disorders, including kidney damage and metabolic diseases), and insomnia are other potential side effects. Rare but potentially fatal toxicity with all NRTIs is pancreatitis, enlarged, fatty liver, and lactic acidosis (accumulation of lactate in the blood and abnormal acid-base balance). Lactic acidosis has been seen in patients taking NRTIs but is more common and more severe in women, people who are obese and people who have been taking nukes for a long time; and more common in people with liver disease, but can occur in people without a history of liver damage. Pregnant women should particularly avoid the combination of Videx and Zerit due to the risk of lactic acidosis. People with lactic acidosis may experience persistent fatigue, abdominal pain or distension, nausea/vomiting, and difficulty breathing or shortness of breath; and enlarged, fatty liver.
People with a history of peripheral neuropathy, pancreatitis or heavy alcohol use should avoid didanosine. Pancreatitis can be life-threatening and may cause pain in the stomach and back, along with nausea, vomiting and blood in the urine. Risks for pancreatitis include: higher than recommended doses of NRTIs, advanced HIV, and alcohol use. Body fat redistribution/accumulation has also been reported with didanosine.
Potential drug interactions: The levels of didanosine are increased by 44–60% when given at the same time as Viread, therefore a dose reduction to 250 mg for Videx is recommended. See Viread page for possibly worrisome information. The combined use of didanosine and AZT, Hivid, or hydroxyurea may increase risk of peripheral neuropathy. Combining didanosine with Zerit or with hydroxyurea, alcohol, Cytovene, or NebuPent may increase risk of pancreatitis. Combining didanosine with Zerit may increase the risk of lactic acidosis. Also, Cytovene and ribavirin substantially increase didanosine levels, and are generally recommended not to be taken together. Videx should be taken on an empty stomach two hours apart from protease inhibitors, Tagamet, Nizoral, Sporanox and dapsone, and one hour apart from Rescriptor, while Videx EC can be taken with them, but still on an empty stomach. With Viread, it may be taken with a light snack (low-fat, 373 calories). The dose of didanosine may need to be increased when taken with methadone.
Tips: Study indicates Videx EC (compared to Videx) may have lower risk of peripheral neuropathy. Either drug taken with Zerit increases the risk of facial wasting. Swallow the capsules whole. The capsules eliminate the bad taste and texture of the tablets and the enteric coating reduces diarrhea. Absorption can be decreased by as much as 50% when taken with food, so take on an empty stomach. Antacids containing magnesium or aluminum may cause adverse side effects if given at the same time as Videx tablets. If you have reduced kidney function, you may require a lower dose. Notify your doctor immediately if peripheral neuropathy is suspected.
Doctor
ddI was originally only available in a chalky chewable tablet that required ingestion on an empty stomach. Reformulation into a coated capsule has eliminated its worst quality and enteric-coating has allowed for once-daily dosing. Like AZT, its use as a mainstay in combination therapy has changed little. However, due to sequencing interests, the order in which it is used over the long haul is beginning to change. Its main side effects remain peripheral neuropathy and pancreatitis. It is generally unadvisable to combine this agent with stavudine due to additive side effects. There is a significant drug-drug interaction with tenofovir which requires a dose reduction of the Videx. Emerging information in some studies suggests Videx-Viread backbones in combination with efavirenz may lead to early treatment failures. A generic formulation is available and may influence use of this drug.—Chad J. Zawitz, MD
Activist
I have a lot of biases against this drug and get criticized for it sometimes. It is known to increase the chances of pancreatitis and neuropathy, and its role on lipoatrophy is not well known yet. The good thing is that it is a great nucleoside that can control HIV in a once-a-day dose. After years of being exposed to the ddI+d4T combo, many people developed facial wasting and general lipoatrophy, and irreversible neuropathy, so the DHHS guidelines panel prohibited its use in that combo. Too bad for those thousands of patients who were exposed to it. I have the strong feeling that we will soon see a ban on the ddI+Viread combo, even at lower ddI doses. This combo can increase the ddI blood levels too high in some, which can increase risk of pancreatitis. Kidney dysfunction due to potential intracellular interaction with Viread is also being observed. For some strange reason that no one can answer for me yet, many people I have met in the past year on that combo are also experiencing involuntary weight loss on ddI+Viread. Just make sure that you are taking a lower dose of 250 mg or below (depends on body weight) if you are taking ddI with Viread and that your T-cells and weight are not decreasing. We have a lot better nucleosides in the developed world now to not have to endure all the risks I have mentioned.—Nelson Vergel
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