Chapter 2 Peripheral nervous system drugs - indirect and mixed sympathomimetics

Question 1

indirect agents

indirect agents

Answer 1

• cause norepinephrine to release from presynpatic terminals
• BUT do not bind to adrenergic receptors

Question 2

mixed sympathomimetics

Answer 2

displace norepinephrine from presynaptic terminals and bind to adrenergic receptors
* induce release of NE and bind as well to receptors
* also can be enhanced via inhibition of degradative enzyme

Question 3

amphetamine and methamphetamine

indirect agents

Answer 3

effects
* vasoconstriction d/t NE release causing inc’d MAP
* inc contraction + lowered HR d/t reflex of MAP
* wakefulness, elation (happy), euphoria (excitement)
* less appetite
* improved simple motor tasks
* stunts growth

clinical uses
attention deficit disorder
parkinson’s disease
narcolepsy (chronic neurological disorder that affects the brain’s ability to control sleep-wake cycles. People with narcolepsy may feel rested after waking, but then feel very sleepy throughout much of the day)
hyperkinetic syndrome of children (symptom complex of hyperactivity, short attention span, distractibility, impulsivity, learning difficulties, other behaviour problems and ‘equivocal’ neurological signs)

undesireable effects
1) HTN
2) cerebral hemorrhage
3) convulsions, tremor, restlessness
4) confusion, anxiety, hallucinations
5) coma

treatment
* anti anxiety agents
* alpha blockers or nitroprusside (nitropress) for HTN
* acidification of urine

note: This is why epinephrine has a greater effect on the heart/cardiac output and lungs/bronchodilation (beta receptors) whereas norepinephrine has a greater effect on the vasculature/vasoconstriction (alpha receptors).

Question 4

ephedrine

mixed agent

Answer 4

• a1 - incresed vasoconstriction l/t MAP inc
• similar to epinephrine (no change in heart rate) – contractility, conduction, automaticity
• clinically used for NARCOLEPSY
• bronchodilation (direct effect, norepinehrine doesn’t cause BRONCODILATION)

clinical uses:
1) asthma (It causes bronchodilation due to the activation of beta-adrenergic receptors in the lungs.)
2) nasal congestion
3) narcolepsy
4) mydriatic – dilates pupil

• of note – less toxicity than amphetamine
• LONGER duration but less potent than epinephrine

Question 5

Hydroxy-amphetamine

mixed agent

Answer 5

• vasoconstriction + inc MAP
• similar to epinephrine (no change in heart rate) – contractility, conduction, automaticity
• More CNS effects than ephedrine, but less than amphetamine
• bronchodilation d/t direct effect