Theophylline and Antiparasitic Drug Interactions: CASE REPORT
A 64-year-old Puerto Rican man (height, 160 cm; weight, 64 kg) was admitted to the hospital on December 25 with an exacerbation of asthma. He was afebrile but had a cough productive of thin white sputum. His chest radiograph was normal. The arterial blood gas values were pH, 7.44; Pcoa, 34; COa content, 24; Po„ 73; and oxygen saturation, 95 percent. Theophylline concentration was less than 14 (tmol/L (2.5 mg/L) and the CBC was 7,600 WBC with 55 percent polymorphonuclear leukocytes, 15 percent eosinophils, 1 percent basophils, 22 percent lymphocytes and 7 percent mono¬cytes. Liver (unction tests were normal throughout the hospitalization. There was no history of cardiac disease and the patient had not used tobacco for many years. Aminophylline was given as a 300 mg intravenous bolus with a continuous infusion at 30 mg/h. Due to his eosinophilia, stool and sputum were analyzed for ova and parasites. On December 29, it was reported that the stool was positive for the rhabdoid larvae of S stercorals.
The sputum culture was negative. The theophylline concentration was 100 p.mol/1 (18 mg/L) on December 29 at an aminophylline infusion rate of 30 mg/ h (half-life of 16 h and clearance of 1.3 L/h). Thiabendazole was started that evening at 1.5 g orally twice a day. On the morning of December 30, the theophylline concentration was 105 |unol/L (19 mg/L). On December 31, the patient was complaining of nausea and a headache. The theophylline concentration was 144 jimol/L (26 mg/L). The theophylline half-life increased to 33 h and clearance had decreased to 0.65 L/h. The aminophylline infusion was discon¬tinued, then restarted at a decreased rate of 20 mg/h. The thiabendazole was discontinued due to development of a skin rash and pyrantel pamoate was substituted. A seven- to ten-day course of antiparasitic therapy was planned because the patient was receiving steroids. The patient was discharged January 6 on a regimen of Theo-Dur, 200 mg orally twice a day, with a theophylline concentration of 44 ftmol/L (8 mg/L). No ova or parasites were found in the patients stool specimen of January 6.