Friday August 28, 1998 - Question 14

Please provide a brief response to each of the following case histories:

Case 1 - A 51 year-old male presents to the emergency department with new onset chest pain.  The patient has diabetes and hypertension and is currently being treated with regular insulin, NPH insulin, and hydrochlorothiazide.  The physician would like to administer sublingual nitroglycerin.  Upon further questioning, it is determined that the patient has taken sildenafil (Viagra) within the last 2 hours and that the chest pain occurred during sexual activity.  The physician is asking you if it is safe to administer the sublingual nitroglycerin and if the hydrochlorothiazide is a problem with sildenafil?  Please comment on why sublingual nitroglycerin is or is not safe to administer to this patient and why hydrochlorothiazide is or is not a problem.

Case 2 -  A 70 year-old female was told to stop taking her mibefradil (Posicor) and that a new prescription for amlodipine (Norvasc) was being called into her pharmacy.  She was told to begin taking amlodipine the next day after stopping mibefradil.  Twenty-four hours after the first dose of amlodipine, the patients presents to the emergency complaining of severe dizziness, facial flushing, and ankle swelling.  Significant vital signs upon admission include heart rate of 55 and blood pressure 98/50.  The physician asks you if mibefradil could still be in high enough serum concentration to cause drug-drug interactions 24 hours after its discontinuance?  The physician would also like to know what the mechanism for drug interactions is with mibefradil?  Please include how the half-life of mibefradil might interfere with drugs added after its discontinuance and the length of time needed to clear mibefradil and its metabolites from the body.

Response