Increase in resting heart rate related to Norvasc?

After 2 years of angina, I was diagnosed in 6/08 with coronary vasospasms/Prinzmetal's angina (suspected diagnosis, no angio w/ergonovine). Anxiety, GERD, mitrovalve prolapse ruled out. Have had thallium stress test, several stress echoes, exercise treadmill, several EKG's all normal. Holter has shown some PVC's but nothing of note.

I was given Amlodipine and gradually increased to 20 mg/day which has decreased my angina attacks to a couple of times a month, a remarkable improvement. For the past few months (probably since the increase to 10mg) I have noticed my resting heart rate has gone from 69-73 bpm to the high 90's. When I am doing simple things like cooking, it raises to 110-115. My BP is now well into a normal range (diagnosed with hypertension several years ago) but the heart rate is higher. I was hospitalized about a month ago when my resting rate was 132 and discharged when it gradually went back to 105 with no explanation. My potassium is low at times but I have been taking a prescribed potassium supplement daily with no change to heart rate. Any advice would be helpful.
30 yr female, no children
non-smoker, moderate drinker
meds: 20 mg Amlodipine
          birth control pill
          potassium supplement
          81 mg aspirin

Thank you,
S. Rosser

[Douglas Bogart, MD]

Norvasc is a vasodilator and as such can cause a reflex tachycardia.  There are other drugs which might be as effective for your problem--like diltiazem--that will not cause the tachycardia.