L290 Exercise-Drug Interactions Flashcards
Physiological changes with exercise that can influence drug pharmacokinetics - list 7 changes
- Redistribution of BF (↑ muscle mass)
- Altered skin temperature and/or altered hydration
- ↑RR and tidal volume
- ↓ gastric emptying
- ↓ intestinal transit time
- Loss of water from plasma into tissues
- Altered metabolic enzyme activity
How does sweat affect PK? Which drugs in particular might this affect?
- Sweat increases absorption
- Transdermal drugs
↓ gastric emptying - how does this affect PK?
↓ delivery of oral drug to the SI → ↓ abs
↓ intestinal transit time - how does this affect PK?
→ speeding up of oral drug movement → ↓ abs
Loss of water from plasma into tissues - how might this affect PK?
- Potentially affects binding proteins, crucial for some drug distribution
Altered metabolic enzyme activity - how might this affect PK? In whom in particular might this occur?
- E.g. in trained individuals - possible consequence for e.g. half-life
↑RR and tidal volume - which drugs might this affect in particular?
Inhaled drugs
Re-distribution of blood flow during physical activity: how it might have implications on ADME
- Absorption: depending on route of administration
- Distribution: increased muscle and skin blood flow
- Metabolism: decreased hepatic blood flow
- Excretion: decreased renal blood flow
Clinical use of insulin
Type 1 diabetes, advanced Type 2 diabetes
Route of admin: insulin
- injection (also inhalation, pump)
Plasma [insulin] with ex vs rest
exercise > rest
Mechanisms for increased plasma [insulin] with ex (2)
a. ↑BF to skin, muscle → ↑absorption
b. ↑ tissue sensitivity to insulin
Factors determining effect of ex on insulin (5)
- Type of insulin
- variable onset and duration
- dosing schedule and route
- Proximity of exercising limbs
- Close to limb → ↑ abs
- Type, duration and intensity of exercise
- Prolonged ex might need glucose supplements
- Amount of muscle mass
- Level of fitness
Determinants of blood glucose during ex with insulin (3)
- Pre-exercise glucose levels
- Patency of counter-regulatory mechanisms
- Carbohydrate supplementation
a. simple or complex
b. rate of absorption
c. timing of administration
Exercise-induced hypoglycaemia - possible mechanisms (3)
- Accelerated insulin absorption from sites near exercising muscles
- Exercise-mediated enhancement of insulin action
Lack of decline in insulin secretion during exercise
- Exercise-mediated enhancement of insulin action
Exercise-induced hyperglycaemia - mechanisms (3)
- Excessive carbohydrate supplementation
2. Too large a reduction in insulin dose
GTN: clinical use
Angina
Route of admin: GTN
- transdermal for prophylaxis
- (sublingual for acute angina)
Plasma [GTN] with ex vs rest
- sauna > exercise > rest
Mechanisms for increased plasma [GTN] during ex (3)
- ↑ skin BF
- ↑ kinetic energy of drugs with ↑ skin temp
- ↑ hydration may improve absorption of drugs
Implications for increased transdermal absorption of GTN (2)
- May provide benefit for exercising patient to minimise exercise-induced angina
- Decline in preload ∴ ↓O2 demand of heart- Potential for vasodilation in skin and exercising muscle to cause
A. Excessive hypotension B. Diversion of coronary BF
- Potential for vasodilation in skin and exercising muscle to cause
Clinical use: salbutamol
Asthma