Medication and Exercise Interactions

The combination of an aging American population along with the widespread prevalence of various chronic diseases increases the likelihood that persons performing exercise will also be taking a prescribed medication. It is important to be aware of the interactions between common medication and the exercise response. Additionally, modifications to the exercise program required due to the interaction between medication and the exercise response need to be highlighted.

Beta-blockers are commonly prescribed medications for hypertension and heart disease. Beta-blockers function by preventing the binding of epinephrine to receptors in the heart. This results in both decreased resting and exercise heart rate (HR) and blood pressure (BP) values. Commonly prescribed beta-blockers include atenolol and metoprolol. The therapeutic effect provided by beta-blockers also means an altered physiological response to exercise. Beta-blocker treatment blunts the usual increases in HR and BP corresponding to higher exercise intensities/workloads. Beta-blockers can also cause glucose intolerance in diabetics by masking the symptoms of hypoglycemia.

An ACE inhibitor (or angiotensin-convertingenzyme inhibitor) is a medication primarily used for the treatment of hypertension. Common ACE inhibitors include captopril, enalapril, and lisinopril. ACE inhibitors relax the blood vessels and lower blood pressure values. Individuals on ACE inhibitor medication have both lower resting and exercise blood pressure values. The interaction between ACE inhibitors and the postexercise blood-pressure response requires persons taking ACE inhibitors and fitness professionals who may be working with them to monitor these values. A beneficial response to exercise is postexercise hypotension, in which systolic blood pressure values can be reduced by 10–20 mmHg for up to 9 hours after the conclusion of exercise. This occurs due to a persistent, but transient, relaxation of the blood vessels. The concern for individuals taking ACE inhibitors is that the combination of the reduction in blood pressure from the medication coupled with naturally occuring postexercise hypotension can result in excessive reductions in blood pressure. This can lead to dizziness and, in rarer instances, temporary loss of consciousness. It is important for persons on ACE inhibitors to consistently adhere to a gradual cool down after every exercise session. One of the classic benefits of a cool down is enhanced blood flow back to the heart and the prevention of blood pooling in the skeletal muscle. A gradual cool down of 5–10 minutes of light aerobic activity permits the body to return to homeostasis and prevents excessive reductions in blood pressure.

Diuretics are another class of medications commonly used for the treatment of hypertension. One of the most common type of diuretics is hydrochlorothiazide (or HCTZ). Diuretics act on the kidney and lead to increased urine output. An upregulation in urine excretion leads to a lower plasma volume, thereby lowering blood pressure. In a similar manner to those on ACE inhibitors, individuals on diuretics will have both lower resting and exercise blood pressure values. A principle concern for individuals taking ACE inhibitors is that the combination of the reduction in blood pressure from the diuretics coupled with the naturally occurring postexercise hypotension can result in excessive reductions in blood pressure. Persons on diuretics who engage in exercise should consistently perform a gradual cool down after all exercise sessions. Another consideration not directly related to the exercise program itself but an important habit for persons taking diuretics is to check their weight daily. This measure will ensure that the prescribed dosage of diuretic is continuing to have its benefits (i.e., increased urine excretion, lowered plasma volume, reduced blood pressure). A sudden change in weight of a few pounds can help alert individuals that they may need to consult their doctor about a possible modification to their medication regimen.

Statins are the most common medication prescribed for high cholesterol. Statins function by inhibiting a key enzyme involved in the production of cholesterol in the liver. Common statins include atorvastatin (Lipitor), simvastatin (Zocor), and pravastatin (Pravachol). Caution is advised when individuals taking statins exercise. Although certainly not common, there are occasional instances where statins are associated with exertional rhabdomyolysis, a condition in which damaged muscle tissue breaks down and releases cellular content (e.g., protein myoglobin) into the blood. These products can be harmful to the kidney. The incidence of exertional rhabdomyolysis is higher in deconditioned individuals performing highintensity exercise, most notably resistance training and eccentric exercises. The condition is also likely to be exacerbated if the high-intensity exercise is also performed in hot, humid environments.

Several preventative measures can be taken to avoid exertional rhabdomyolysis:

Oral hypoglycemics are a class of medications commonly prescribed for type 2 diabetic individuals.

Three major groups of oral hypoglycemics are used to control blood glucose: (1) ß-Cell stimulants for insulin release; (2) drugs to improve insulin sensitivity; and (3) drugs that decrease intestinal absorption of carbohydrates. ß-cell stimulants function by inciting insulin release from the pancreas. These medications are taken with meals and help alleviate excessive increases in postmeal blood-glucose levels. The latter two oral hypoglycemic categories have little effect on the exercise response. A few common ß-cell stimulants include glipizide and glyburide. The transport of glucose from the blood into the muscle cell is facilitated by the transporter protein GLUT-4. These transporter proteins respond to two signals—insulin and exercise. The insulin stimulation from ß-cell stimulants, when combined with exercise, can increase the potential for hypoglycemia (i.e., low blood glucose levels).

The most important modification to the exercise program for persons taking oral hypoglycemics is frequent monitoring of blood-glucose values. Initially, this should include checking levels before, during, and after exercise. Once it has been established how much blood glucose values typically drop for a usual exercise session and provided these changes are within an acceptable range, less frequent monitoring will be required. Typically, it is the responsibility of the exercising individuals to bring their own glucometers and glucose strips, which should have been prescribed by a doctor.

Lance C. Dalleck, PhD