The following section will consist of a brief case history followed by a question and discussion section.  Each case history is an excerpt from a real case involving CYP-450 mediated events.  Use your knowledge of the CYP-450 system and the tables of CYP-450 substrates, inhibitors and inducers to answer the following questions.

Thursday September 17, 1998 - Question 6

A 54 year-old female with a history of seasonal allergic rhinitis, obsessive compulsive disorder (OCD), hypertension, and chronic angina, presents to her physician with new onset dizziness.  Her long-term medications include loratidine (Claritin) for seasonal allergic rhinitis, fluvoxamine (Luvox) for OCD, nitroglycerin transdermal patch for angina, and hydrochlorothiazide for hypertension.  She was recently prescribed felodipine (Plendil), an extended release calcium channel blocker, for worsening angina.  The patient took her first dose of felodipine three days before her dizziness began.  Felodipine was discontinued immediately and the patient’s dizziness resolved over the next two days.

Which of the following statements concerning the above case history is true?

A. Drug interactions are not expected between the above agents.
B. The patient’s dizziness is probably related to her hydrochlorothiazide.
C. Felodipine is most likely inhibiting the metabolism of nitroglycerin.
D. Accumulation of loratidine may be responsible for this patient’s dizziness.
E. Accumulation of felodipine may be responsible for this patient’s dizziness
 
 

Discussion