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Exercise (W30) > L290 Exercise-Drug Interactions > Flashcards

L290 Exercise-Drug Interactions Flashcards

1
Q

Physiological changes with exercise that can influence drug pharmacokinetics - list 7 changes

A
  1. Redistribution of BF (↑ muscle mass)
  2. Altered skin temperature and/or altered hydration
  3. ↑RR and tidal volume
  4. ↓ gastric emptying
  5. ↓ intestinal transit time
  6. Loss of water from plasma into tissues
  7. Altered metabolic enzyme activity
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2
Q

How does sweat affect PK? Which drugs in particular might this affect?

A
  • Sweat increases absorption

- Transdermal drugs

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3
Q

↓ gastric emptying - how does this affect PK?

A

↓ delivery of oral drug to the SI → ↓ abs

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4
Q

↓ intestinal transit time - how does this affect PK?

A

→ speeding up of oral drug movement → ↓ abs

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5
Q

Loss of water from plasma into tissues - how might this affect PK?

A
  • Potentially affects binding proteins, crucial for some drug distribution
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6
Q

Altered metabolic enzyme activity - how might this affect PK? In whom in particular might this occur?

A
  • E.g. in trained individuals - possible consequence for e.g. half-life
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7
Q

↑RR and tidal volume - which drugs might this affect in particular?

A

Inhaled drugs

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8
Q

Re-distribution of blood flow during physical activity: how it might have implications on ADME

A
  • Absorption: depending on route of administration
  • Distribution: increased muscle and skin blood flow
  • Metabolism: decreased hepatic blood flow
  • Excretion: decreased renal blood flow
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9
Q

Clinical use of insulin

A

Type 1 diabetes, advanced Type 2 diabetes

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10
Q

Route of admin: insulin

A
  • injection (also inhalation, pump)
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11
Q

Plasma [insulin] with ex vs rest

A

exercise > rest

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12
Q

Mechanisms for increased plasma [insulin] with ex (2)

A

a. ↑BF to skin, muscle → ↑absorption

b. ↑ tissue sensitivity to insulin

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13
Q

Factors determining effect of ex on insulin (5)

A
  1. Type of insulin
    • variable onset and duration
    • dosing schedule and route
  2. Proximity of exercising limbs
    • Close to limb → ↑ abs
  3. Type, duration and intensity of exercise
    • Prolonged ex might need glucose supplements
  4. Amount of muscle mass
  5. Level of fitness
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14
Q

Determinants of blood glucose during ex with insulin (3)

A
  1. Pre-exercise glucose levels
    1. Patency of counter-regulatory mechanisms
    2. Carbohydrate supplementation
      a. simple or complex
      b. rate of absorption
      c. timing of administration
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15
Q

Exercise-induced hypoglycaemia - possible mechanisms (3)

A
  1. Accelerated insulin absorption from sites near exercising muscles
    1. Exercise-mediated enhancement of insulin action
      Lack of decline in insulin secretion during exercise
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16
Q

Exercise-induced hyperglycaemia - mechanisms (3)

A
  1. Excessive carbohydrate supplementation

2. Too large a reduction in insulin dose

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17
Q

GTN: clinical use

A

Angina

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18
Q

Route of admin: GTN

A
  • transdermal for prophylaxis

- (sublingual for acute angina)

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19
Q

Plasma [GTN] with ex vs rest

A
  • sauna > exercise > rest
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20
Q

Mechanisms for increased plasma [GTN] during ex (3)

A
  1. ↑ skin BF
    1. ↑ kinetic energy of drugs with ↑ skin temp
  2. ↑ hydration may improve absorption of drugs
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21
Q

Implications for increased transdermal absorption of GTN (2)

A
  1. May provide benefit for exercising patient to minimise exercise-induced angina
    - Decline in preload ∴ ↓O2 demand of heart
    1. Potential for vasodilation in skin and exercising muscle to cause
      A. Excessive hypotension B. Diversion of coronary BF
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22
Q

Clinical use: salbutamol

A

Asthma

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23
Q

Route of admin: salbutamol

A

Inhalation

24
Q

Plasma [salbutamol] with ex vs rest

A

exercise > rest

25
Q

Mechanisms for ↑ plasma [salbutamol] during ex (3)

A
  1. ↑ RR
    1. ↑ pulmonary blood flow
    2. ↑ epithelial permeability
26
Q

Implications of ↑ plasma [salbutamol] (2)

A
  1. may provide benefit for exercising patient to minimise exercise-induced asthma
  2. *despite higher BA, because of ↑BF and RR, bronchodilator effects are less prolonged - need more frequent dosing!
27
Q

Effects of exercise in the gut are…

A

variable

28
Q

List to possible effects of exercise on gut

A

A. Inhibits gastric emptying

B. ↑ intestinal motility

29
Q

Which cohort is not affected by decreased gastric emptying with ex?

A

Trained athletes - adaptation occurs

30
Q

Clinical use: warfarin

A

Anticoagulant

31
Q

Route of admin: warfarin

A

Oral

32
Q

INR (no PK data) with warfarin in ex vs rest

A

exercise

33
Q

Mechanisms of decreased INR (unconfirmed) with ex (using warfarin) (2)

A
  1. ↑ binding of warfarin to albumin

2. ↑ metabolism with training

34
Q

Implications of decreased [warfarin] with ex

A

↓ free warfarin, ↓ INR (i.e. shorter clotting time) → ↑ risk of thrombosis with ex

35
Q

Clinical use: digoxin

A

heart failure, atrial arrhythmia

36
Q

Route of admin: digoxin

A

Oral

37
Q

plasma/muscle [digoxin] with ex vs rest

A
  • Plasma [digoxin]: exercise less than rest

- Muscle [digoxin]: ex > rest

38
Q

Mechanisms of ↓ plasma [digoxin] with ex

A

redistribution due to increased binding to skeletal muscle

39
Q

Implications for ↓ plasma [digoxin] with ex

A

• reduced efficacy to increase contractility and control rate

40
Q

TI and Vd of digoxin

A
  • narrow TI

- high Vd - high binding affinity to skeletal muscle normally

41
Q

Clinical use of b-blockers

A

hypertension, angina

42
Q

Route of admin of b-blockers

A

oral

43
Q

[b-blocker] with ex vs rest

A

Effect of short duration exercise will vary with drug:
• Plasma [propranolol]: exercise > rest
- Propranolol NS β blocker
• Plasma [atenolol]: exercise > rest
- Atenolol S β blocker
• Plasma [carvedilol]: exercise = rest
- Carvedilol NS β and α blocker

44
Q

Mechanisms of ↑ plasma [beta-blockers] with ex (2)

A
  1. ↓ hepatic clearance for propranolol (→ ↓ metabolism)

↓ renal clearance for atenolol (→ ↓ excretion)

45
Q

Implications of ↑ plasma [beta-blockers] with ex

A
  • ↑ risk of exercise-limiting adverse effects e.g. bronchoconstriction, fatigue (from NS block of b2-mediated skeletal muscle VD)
    • → patient’s ability to exercise is more difficult → poor exercise compliance: important to encourage compliance because this effect tapers off
46
Q

Why use drugs in sport? (2 reasons)

A
  1. Hide the use of other drugs
    • Diuretics (→ ↓ [banned substance] in urine)
  2. Improve performance
47
Q

For a substance to be prohibited in sport, what conditions must it meet?

A

Must meet two of the following three conditions:

1. Potential to enhance, or does enhance performance in sport 
2. Potential risk to the athlete’s health  3. World Anti-Doping Agency has determined that the substance or method violates the spirit of sport
48
Q

Therapeutic Use Exemptions (TUE): what are they?

A
  • Available if an athlete suffers an acute or chronic medical condition that a doctor can only treat with a prohibited substance
    • Athletes must receive approval before using substance
49
Q

Clinical use: b2-agonists

A

Asthma

50
Q

Route of admin: b2-agonists

A

Inhalation

51
Q

Potential advantages in sport with b2-agonists (3)

A

With systemic administration:
• ↑skeletal muscle BF → ↑ O2 supply and lactic acid removal reduces fatigue
• Anabolic effect: ↑ muscle mass ( → strength)
• Catabolic effect: ↓ body fat

52
Q

Potential adverse effects with b2-agonists (2)

A
  1. Tachycardia: NS activation of cardiac b1-adrenoceptors

2. Muscle tremor: activation of skeletal muscle b2-adrenoceptors

53
Q

Status in Sport: b2-agonists

A
  • Prohibited for any route other than inhalation

* No TUE required for salbutamol (maximum dose 1600 mg/day, urine concentration

54
Q

Potential advantage in sport: GCS (1)

A

• Anti-inflammatory action can mask pain so athlete can compete despite injury

55
Q

Potential disadvantage in sport and adverse effects: GCS (5)

A
  1. Damage to tissue before full recovery (bc can’t heed body’s warning signs)
    1. Chronic use can cause:
      A. Osteoporosis
      B. Growth suppression (children)
      C. Skin fragility
      Increased infections
56
Q

Status in Sport: GCS

A

• Approved without a TUE
- Topical use with skin creams, eye drops, topical mouth applications, nasal sprays and ear drops
- Inhalation for asthma (certain preparations only)
• Require abbreviated TUE if administered via intra-articular route
• Prohibited TUE required for systemic administration (oral, intravenous, rectal)

Exercise (W30) (11 decks)

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