运动和药物会相互影响吗？

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Exercise and Medication: How Do They Interact?Karla Fisher and Roni Jamnik, York University
Originally published in the CSEP member newsletter, Communiqué, November 2007.
Introduction
As exercise becomes increasingly accepted as a form of disease management, the importance of understanding how exercise interacts with medications becomes vital.  The pharmacokinetics of medications can have a notable impact on both a person´s ability to exercise and his/her physiological response to exercise.  Conversely, the acute and chronic physiological responses that occur during exercise can have profound effects on the absorption, distribution, metabolism and excretion of both prescription and over the counter drugs.  Therefore, it is important for fitness professionals to understand the purpose of common medications and their effects on the body both at rest and during exercise.  Conditions for which exercise is commonly prescribed as a form of disease management include cardiovascular disease, diabetes and pulmonary disease. Each of these conditions typically involves medication therapy that could influence exercise response or alternatively, the action of the medication could be affected by exercise.
Cardiovascular Disease; Beta Blockers
Beta blockers are a group of drugs commonly used to treat various forms of cardiovascular disease including hypertension, congestive heart failure, arrhythmias, angina and myocardial infarction (1).  These drugs act to reduce the activity of the sympathetic nervous system causing a lower resting heart rate and blood pressure.  Although exercise presents a strong stimulus to increase heart rate and blood pressure, it is not strong enough to completely override the inhibitory effects of beta blockers (3).  In addition to a reduced heart rate and blood pressure response throughout exercise, there is a decrease in the maximum heart rate.   The maximum resultant heart rate on beta blockers is an interaction between the degree of beta-blockade and the individual´s intrinisic maximum heart rate.  The maximum heart rate may be reduced by the 30 – 40 % of the age predicted maximum. (3).  
Understanding how heart rate is affected is particularly important when determining an appropriate training zone.  For example, using an upper heart limit of 130 bpm, rather than the customary “220-age.”  Rating of Perceived Exertion (Borg Scale) and monitoring of work accomplished (distance covered, for example) are good alternative indicators of training intensity for individuals on beta blockers.  In addition, the altered heart rate makes the estimation of aerobic fitness (VO2max) entirely inappropriate when using the indirect method of submaximal heart rate monitoring. Direct VO2max testing on individuals taking beta blockers is possible; however the limitation on maximum heart rate leads to a diminished cardiac output and consequently a reduced VO2max.  Because beta blockers can also limit exercise performance through the exacerbation of asthma, individuals with pulmonary disease should be monitored closely.  Conversely, exercise tolerance may be increased as a result of beta blocker administration in those suffering from chest pain, since inhibition of the sympathetic nervous system leads to a reduction in the level of ischemia in cardiac tissue, causing an increase in the angina threshold (1).
Diabetes; Insulin
IInsulin is a life-sustaining drug used by patients with diabetes mellitus. These individuals require exogenous insulin to maintain appropriate blood glucose levels (1).  Insulin alters the glycemic response to exercise (2) and therefore, special considerations need to be made when dealing with exercising diabetics.  Because physical activity facilitates glucose transport in the absence of insulin, overmedicating prior to exercise places a diabetic at risk for hypoglycaemia, which can lead to diabetic shock.  Additionally, many studies show that the absorption of subcutaneously injected insulin is enhanced by exercise due to its dependence on local blood flow and the massaging effect of the working muscles (4,5).  Appropriate steps to prevent hypoglycaemia include reducing insulin dosage prior to exercise and/or consuming a carbohydrate snack immediately prior to activity.
Pulmonary Disease; Bronchodilators & Anti-Inflammatory Agents
The two most commonly prescribed respiratory drugs include bronchodilators and anti-inflammatory agents. There are many types of bronchodilators including beta-receptor agonists, methylxanthines and anticholinergics.  Although each bronchodilator acts via a different pathway, they all result in dilation of the large airways through relaxation of bronchial smooth muscle.  Anti-inflammatory agents include inhaled corticosteroids and mast cell stabilizers.  Both agents are administered through inhalation and are used as a prophylactic to treat persistent or chronic asthma by suppressing bronchial inflammation (2).  
There has been little research on how exercise affects the pharmacokinetics of respiratory medications.  During exercise, blood flow redistribution away from the liver and kidneys results in a reduced clearance time for certain medications, including theophylline; inappropriate dosage can lead to toxicity, causing problems of rapid heart rate, nausea, vomiting, diarrhea and headache (1).  Cautionary steps prior to initiating an exercise program should include discussion with the client´s physician.
Use of nearly all types of respiratory drugs will improve exercise tolerance by reducing the resistance to breathing in individuals suffering from pulmonary diseases such as asthma, chronic bronchitis, emphysema and COPD.  However, exercise monitoring can be affected because many of these drugs cause alterations in both resting and exercising heart rate (3); this should be considered before using heart rate to monitor training intensity and/or provide estimates of aerobic fitness based on the heart rate response.
Summary
These are only a few examples of the multitude of prescription and non-prescription drugs that are being used by people of all ages and fitness levels.  To avoid complications that could arise as a result of exercise interaction and drug pharmacokinetics, it is vitally important for fitness professionals to have an understanding of all drugs being taken by a client.  Additionally, the lack of research evidence regarding possible drug and exercise interaction necessitates the close monitoring of clients undergoing pharmacotherapy.  This includes tracking heart rate, rating of perceived exertion and blood pressure before, during and after exercise sessions.  We strongly recommend that patients undergoing medication therapy who are considering exercise training seek the guidance of a CSEP Certified Exercise Physiologist™ and discuss the proposed exercise program with their physician.
References:

• 1. Lenz, T.L., Lenz, N.J., Faulkner, M.A.  Potential Interactions between Exercise and Drug Therapy. Sports Med 2004; 34 (5); 293-306
• 2. Durstine, J.L., Moore, G.E. (2003) ACSM´s Exercise Management for Persons with Chronic Diseases and Disabilities Second Edition. Windsor, ON: Human Kinetics.
• 3. Reents, Stan. (2000) Sport & Exercise Pharmacology. Windsor, ON: Human Kinetics.
• 4. Peter, R., Luzio, S.D., Dunseath, G., et al. Effects of Exercise on the Absorption of Insulin Glargine in Patients with Type 1 Diabetes.  Diabetes Care 2005; 28;      560-565
• 5. DeFronzo, R.A., Ferranninni, E., Sato, Y., Felig, P., Wahren, J. Synergistic Interaction between Exercise and Insulin on Peripheral Glucose Uptake. J. Clin. Invest. 1981; 68; 1468-1474
  

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