Autonomic NS 5: Ephedrine & Amphetamine Flashcards
Chemistry of Ephedrine
Natural alkaloid from ephedra plant
oral adminstration of Ephedrine
effective & stable
Ephedrine can be injected ____
subcutaneous & intramuscular
Local eye drop of ephedrine
diffusion can occur
Describe distribution of ephedrine
can pass blood brain barrier & have an effect on CNS
Describe metabolism of ephedrine
Generally: slow metabolism with long duration
* Metabolized only by the liver
* not destroyed by MAO (as it is not a Catecholamine)
* May even inhibit MAO (so shouldn’t be given with MAO inhibitors)
Describe excretion of Ephedrine
- in urine
- Mainly unchanged
- Acidification of urine increases its renal excretion
renal Excretion of Ephedrine can be increased by
Acidification of Urine
difference between Ephedrine & Adrenaline (epinephrine) in duration
Ephedrine has longer duration, due to it not being broken down by MAO
difference between Ephedrine & Adrenaline (epinephrine) in Distribution
- Ephedrine can be absorbed orally (through GIT), adrenaline can’t
- Ephedrine can pass BBB thus has an effect on CNS, adrenaline doesn’t
difference between Ephedrine & Adrenaline (epinephrine) in local application on the eyes
- Ephedrine causes Mydrasis
- Adrenaline has no effect when applied locally on the eye due to no diffusion
Mixed acting sympathomemtic
Ephedrine
effect of repetitive adminstration of ephedrine
- Tolerence
- Tachyphylaxis (decreased response) ( effect is reduced due to depletion of NA vesicles)
- (at short intervals) dimenishes/ removes the hypertensive response
Explain why, despite having similar pharmacodynamics, ephedrine is contraindicated with enlarged prostate, but Adrenaline isn’t
Adrenaline is a Catecholamine, which means it can be broken down by MAO, therefore its effect is rapid with shorter duration, thus wont affect urine retention
Action of Ephedrine
stimulates Alpha & Beta with longer duration than adrenaline, and weaker effect on Beta
Mechanism of Ephedrine
Dual Action:
* direct: acts on Alpha & Beta
* Indirect: facilitates release of NA from vesicles
Mainly indirect
effect of Ephedrine on heart
Increase all cardiac properties
Like adrenaline
effect of Ephedrine on Blood vessels
- general Vasoconstriction of skin & mucosal membrane (alpha 1)
- Vasodilatation of Cornary & skeletal vessels (Beta1)
effect of Ephedrine on blood pressure
(noradrenaline mota5afy= weak Beta, strong alpha)
* Elevate both systolic and diastolic blood pressure
* when given with alpha blocker, there is no reversal/ no beta effect
* Alpha blockers completely abolish pressor effect when given with Epherine
effect of Ephedrine on smooth muscles
Same as Epinephrine/ Adrenaline
* eye–> mydrasis
* Bronchi—> bronchdilatation
* Urinary tract—-> relaxation of wall
* Sex organs —–> male=ejaculation
effect of Ephedrine on Skeletal muscle
- Facilitate Neuromuscular transmission
- Causes Vasodilatation of skeletal vessels Used to treat Myasthenia gravis (long duration)
Explain why ephedrine is used to treat myathenia gravis but adrenaline isn’t
despite both causing Vasodilatation of skeletal blood vessels, Adrenaline is broken down by MAO, Ephedrine isn’t, therfore it has a duration long enough to treat gravis
Describe effect of ephedrine on CNS
- Analeptic= stimulates respiratory & vasomotor centers in CNS (used in treating morphine overdose)
- stimulates Cerebral cortex & reticular formation (causes anxiety & insomnia)
Local use of Ephedrine
- Epistaxis (Hemostatic effect)
- Nasal decongestant (pseudoephedrine is better to avoid irritation)
- Mydrasis (local on eye)
