L16 Therapeutic Uses Of Sympathomimetic Drugs Flashcards
Example of endogenous catecholamines
Adrenaline, noradrenaline, dopamine
Effect of adrenaline act on the receptors
alpha-1 receptor: vasoconstriction
beta-1 receptor: increases heart rate and cardiac contractility
- causes increase in systolic pressure
beta-2 receptor: vasodilation
- decrease peripheral resistance
- decrease diastolic pressure
Effect of noradrenaline on receptors
- significant effect on alpha-1 and beta-1 receptors
- increase total peripheral resistance
- increase diastolic pressure
- activate compensatory baroreflex
- results in decrease heart rate
- little effect on beta-2 receptor
Why is compensatory baroreflex not activated on adrenaline?
- adrenaline stimulates a1, b1, and b2 with relatively balanced potency but noradrenaline has a low effect on b2 receptor
- noradrenaline strong vasoconstriction effect on a1 receptor leads to significant increase in BP
- adrenaline with its balanced vasoconstriction and vasodilation does not cause increase in BP, thus does not activate compensatory baroreflex
Dose-dependent effects on dopamine
Low: D1 (vasodilation, increase renal blood flow)
Intermediate: D1 and B1 ( increase renal blood flow, heart rate and cardiac output)
High: a ( vasoconstriction, increase BP)
Effects of dopamine
- regulate sodium excretion and renal function
- important neurotransmitter in CNS, involved in stimulus relevant to addiction
- target receptors for antipsychotic drugs
Types of indirect-acting drugs
- releaser
- uptake inhibitors
Types of releaser/ displacer
- tyramine
- methylphenidate
- amphetamine
- methamphetamine
- phenmetrazine
- modafinil
Function of phenmetrazine
- anorexiant
Function of methylphenidate
- ADHD
Function of modafinil
- narcolepsy
Function of amphetamine
- keep alert and depressant effect on appetite
Drugs to treat acute hypotension. How?
- B1 agonists: dobutamine, dopamine, noradrenaline
- increase cardiac output and blood flow
What is chronic orthostatic hypotension? Drug to treat chronic orthostatic hypotension. How? Can be caused by what medication?
- When standing, gravity causes the blood to pool in the veins of the leg and lower body. Pooling decrease amount of blood returning to heart (venous return). Thus, reflex sympathetic activation to decrease BP by active autonomic nervous system to cause vasoconstriction and increase BP.
- Caused by TCAs (imipramine), alpha blockers, diuretics, diabetes
- treat by alpha agonists (midodrine, ephedrine, phenylephrine, droxipa) to cause vasoconstriction to increase peripheral resistance
What drug can be used to treat resuscitation cardiac arrest?
Adrenaline by improving the chance of returning to spontaneous circulation
Drug for cardiac stress test
Dobutamine (B1 agonist)
- increase HR, myocardial contractility
- promotes coronary and systemic vasodilation
- increase heart rate
- enhance blood flow to the heart and other tissue
- detect ischemia in myocardium
- Used in patients unable to exercise
Catecholamine Reuptake Inhibitors
Cocaine, Atomoxetine, Sibutramine, Duloxetine
Cocaine
- inhibit NA and DA
- local anesthetic with a peripheral sympathomimetic action
- readily enters CNS
- more intense than amphetamine
Atomoxetine
- treat ADHD
- inhibit NA reuptake transporter
Sibutramine
- inhibit NA and serotonin
- appetite suppressant
- remove from market due to stroke
Duloxetine
- inhibit NA and serotonin
- antidepressant
- treatment of pain in fibromyalgia
Which drug is mydriatic agent but do not cause cycloplegia
phenylephrine
Used in glaucoma and lower IOP
- brimonidine, apraclonidine
Used for urinary incontinence in elderly and children with enuresis(bed wetting)
ephedrine
