Exercise-Drug Interactions Flashcards
Vasoconstriction is mediated by
alpha 1 receptors
Vasodilation is mediated by
beta 2 receptors
The effects of redistributed blood flow in exercise affect absorption
based on route of administration
The effects of redistributed blood flow in exercise affect distribution by
increased muscle and skin blood flow
The effects of redistributed blood flow in exercise affect metabolism by
decreased hepatic blood flow
The effects of redistributed blood flow in exercise affect excretion by
Decreased renal blood flow
What is the risk of exercise in insulin-dependent diabetes?
plasma insulin can rise during exercise and tf glucose control may be dysregulated
What are mechanisms of exercise-induced hypoglycaemia?
Accelerated insulin absorption from sites near exercising muscles; exercise-mediated enhancement of insulin action; lack of decline in insulin secretion during exercise (ie secrete insulin during exercise)
What are mechanisms of exercise-induced hyperglycaemia?
Excessive CHO supplementation; too large a reduction in insulin dose pre-exercise
What is the risk in using transdermal glyceryl trinitrate in exercise (or hot environments)?
plasma levels of GTN can be increased by the associated: inc skin blood flow, inc kinetic energy of drugs with inc skin temperature, inc hydration which improves absorption of drugs with diffusion rate-limited absorption
What are the implications of increased transdermal absorption of GTN in exercise?
may be beneficial by further minimizing risk of exercise-induced angina; potential for vasodilation in skin and exercising muscle to cause excessive hypotension and divert coronary blood flow esp in hot environments - can get precipitous hypotension (severely low BP)
Salbutamol
works on B2 receptors in airways to cause bronchodilation
What are the consequences of taking salbutamol prior to or during exercise?
plasma levels can become increased due to the increased respiratory rate, increased pulmonary blood flow, and increased epithelial permeability
What are the implications of increased absorption of salbutamol in exercise?
May provide benefit by minimizing exercise-induced asthma; despite higher bioavailability though, bronchodilator effects are less prolonged - it wears off quicker so dosing needs to be more frequent
How does exercise impact the gut?
inhibits gastric emptying; increases intestinal motility to reduce transit time; decreases splanchnic blood flow
How does inhibition of gastric emptying in exercise affect drugs in the gut?
reduces drug delivery to the SI tf decreasing absorption; adaptation occurs in trained athletes
How does increased intestinal motility in exercise affect drugs in the gut?
reduced transit time means less time for absorption of lipophilic drugs
How does decreased splanchnic blood flow in exercise affect drugs in the gut?
more time for absorption of drugs where diffusion is the rate limiting step
What are the risks of warfarin in exercise?
Increased bruising and decreased INR (clotting time)
How is INR purportedly shortened by exercise?
Warfarin is more bound to plasma albumin because of fluid loss; may be an increase in metabolism of the drug with training; in both, get decreased free warfarin = more clotting/decreased INR
What is the implication of decreased INR with exercise?
Increased clotting and risk of thrombosis
How does exercise affect levels of digoxin in the body?
Digoxin has a high volume distribution tf goes into muscle, not much in plasma; in exercise, there is reduced plasma digoxin but increased distribution and binding to skeletal muscle
What is the mechanism of decreased plasma levels of digoxin in exercise?
Redistribution due to increased binding to skeletal muscle tf not much is left in plasma
What are the implications of decreased plasma digoxin in exercise?
Digoxin is used to maintain contractility or control HR - can dysregulate this, lead to arrythmias
