Acute onset of pancreatitis with concomitant use of tenofovir and didanosine.
OBJECTIVE
To report a case of pancreatitis associated with the combined use of didanosine and tenofovir.


METHODS
A 51-year-old white man with HIV was initiated on antiretroviral therapy with didanosine 250 mg/day, tenofovir 300 mg/day, lamivudine 300 mg/day, stavudine 60 mg/day, and efavirenz 600 mg/day. Didanosine was prescribed at a reduced dosage due to the known interaction with tenofovir. Despite this dosage adjustment, the patient developed acute pancreatitis 10 weeks after antiretrovirals were initiated. Pancreatitis resolved spontaneously after antiretroviral discontinuation.


CONCLUSIONS
Our report of didanosine-induced pancreatitis secondary to concurrent use with tenofovir is the third reported case that utilized a reduced didanosine dosage. Five previous pancreatitis reports have been described using full-strength didanosine with tenofovir. The exact mechanism of action for this interaction is unknown. Utilizing the Naranjo probability scale to assess causality, a possible adverse drug reaction was determined.


CONCLUSIONS
Tenofovir and didanosine may be used cautiously in antiretroviral combination therapy. Reduced didanosine dosage (250 mg) should be used to reduce serum didanosine concentrations and subsequent toxicities. Practitioners should be aware that a significant drug interaction with resulting pancreatitis may occur even when a reduced dosage is prescribed.
Kirian
Margaret A
MA
Department of Pharmacy, Cleveland Clinic Foundation, Cleveland, OH, USA.
Higginson
Robert T
RT
Fulco
Patricia Pecora
PP
D000208:Acute Disease; D000225:Adenine / Q000009:adverse effects* / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D019380:Anti-HIV Agents / Q000009:adverse effects* / Q000493:pharmacokinetics; D016049:Didanosine / Q000009:adverse effects* / Q000493:pharmacokinetics; D004359:Drug Therapy, Combination; D015658:HIV Infections / Q000188:drug therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000009:adverse effects* / Q000493:pharmacokinetics; D010195:Pancreatitis / Q000139:chemically induced*; D000068698:Tenofovir
D019380:Anti-HIV Agents; D063065:Organophosphonates; D000068698:Tenofovir; D000225:Adenine; D016049:Didanosine