Antihistamines such as Benadryl (diphenhydramine), Claritin (loratadine), Zyrtec (cetirizine), commonly used to treat an allergic reaction, have no effect on heart rate and blood pressure during rest and exercise. They also have no effect on exercise capacity. Cold medicine with sympathomimetic agents may increase heart rate or blood pressure during rest and exercise.
Levothyroxine or brand name Synthroid, a thyroid medication, increases heart rate and blood pressure during rest and exercise. It has no effect on exercise capacity except if a patient has angina, it may become worse.
Alcohol, has no effect on heart rate but chronic use of alcohol increases blood pressure during rest and exercise. Alcohol has no effect on exercise capacity.