Drug Interactions Corner

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Didanosine–Tenofovir: Severe Drug Interaction

KEY POINT

Concomitant therapy with tenofovir (Viread—Gilead Sciences) and didanosine (Videx— Bristol-Myers Squibb) has been associated with increased didanosine toxicity (e.g., lactic acidosis, pancreatitis, and peripheral neuropathy) and poor therapeutic outcomes (e.g., decreased CD4+ T-cell counts and reduced virologic response) in some patients. Didanosine dosage adjustments and close monitoring are required during combined therapy.

SOURCES

Barrios A et al. Paradoxical CD4+ T-cell decline in HIV-infected patients with complete virus suppression taking tenofovir and didanosine. AIDS. 2005;19:569–75.

Kirian MA et al. Acute onset of pancreatitis with concomitant use of tenofovir and didanosine. Ann Pharmacother. 2004;38:1660–3.

Tung MY et al. The durability of virological success of tenofovir and didanosine dosed at either 400 or 250 mg once daily. HIV Med. 2005;6(3):151–4.

Murphy MD et al. Fatal lactic acidosis and acute renal failure after addition of tenofovir to an antiretroviral regimen containing didanosine. Clin Infect Dis. 2003;36:1082–5.

Rivas P et al. Drug points: fatal lactic acidosis associated with tenofovir. BMJ. 2003;327:711.

Guo Y, Fung HB. Fatal lactic acidosis associated with coadministration of didanosine and tenofovir disoproxil fumarate. Pharmacotherapy. 2004;24:1089–94. 

Perez-Elias MJ et al. High virological failure rate in HIV patients after switching to a regimen with two nucleoside reverse transcriptase inhibitors plus tenofovir. AIDS. 2005;19:695–8.

Negredo E et al. Unexpected CD4 cell count decline in patients receiving didanosine and tenofovir-based regimens despite undetectable viral load. AIDS. 2004;18:459–63. 

Karrer U et al. No evidence for a poor immunologic response in patients treated with antiretroviral therapy containing tenofovir and didanosine at a weight adjusted dose. Presented at the 12th Conference on Retroviruses and Opportunistic Infections, February 22–25, 2005, Boston. Abstract 588.