Adrenergic 2 Flashcards
- What is Clonidine?
Partial a2-selective agonist that activates CENTRAL a2-adrenoreceptors. By activating central receptors it therefore passes through the BBB, then activates the pre-synaptic M2 receptors which are inhibitory therefore decreasing sympathetic outflow/release of NE. This drug is used to treat high blood pressure. It’s adverse side effects are lethargy, sedation and xerostomia.
- What is Methyldopa?
Methyldopa is an a2-selective agonist that activates CENTRAL a2-adrenoreceptors. It is taken up by noradrenergic neurons and converted to a-methylnorepinephrine which is what activates the receptors. This drug is used to decreased blood pressure and is the drug of choice for HTN TREATMENT DURING PREGNANCY. Adverse side effects include sedation, impaired mental concentration and xerostomia.
- What is Brimonidine?
Brimonidine is a highly selective a2 agonist used to lower intraocular pressure in glaucoma. It’s delivery method is eye drops. It reduces aqueous humor production AND increases outflow.
- What is the role of a releasing agent (type of indirect-acting adrenergic agonist)?
Releasing agents cause NE release from presynaptic terminals thereby potentiating effects of norepinephrine produced endogenously. Ex. amphetamine, methylphenidate, tyramine
- What is Amphetamine?
Amphetamine is an indirect-acting adrenergic agonist that acts as a releasing agent. It has CENTRAL stimulatory action and can increase blood pressure by a-agonist action on vasculature as well as B-stimulatory effects on the heart.
- What is Methylphenidate?
Methylphenidate is a structural analogue of amphetamine that acts as an indirect-acting adrenergic agonist that acts as a releasing agent. It is widely used to treat ADHD in children.
- What is tyramine?
Tyramine is an indirect-acting adrenergic agonist that acts as a releasing agent. It is found in fermented foods such as ripe cheese and Chianti wine. When consumed it is usually oxidized by MAO. When patients consume these products while taking MAO inhibitors it can precipitate serious vasopressor episodes with increasing blood pressure, causing headache, etc (“cheese effect”).
- What is cocaine?
Cocaine is an uptake inhibitor that blocks monoamine reuptake thereby allowing them to accumulate in the synaptic space. This results in potentiation and prolongation of central and peripheral action of the monoamines.
- What is Atomoxetine?
Atomoxetine is an uptake inhibitor selective for norepinephrine reuptake transporters. It is indicated for the treatment of ADHD.
- What is Modafinil?
Modafinil is an uptake inhibitor that inhibits NE and dopamine transporters thereby increasing synaptic concentrations of NE, dopamine, serotonin and glutamate and decreasing GABA levels. The mode of action is not fully known. It is used for treatment of narcolepsy by acting as a psychostimulant.
- What is ephedrine? (mechanism)
Ephedrine stimulates a and B receptors causing the release of NE from nerve endings. This is not a catecholamine thereby is not broken down by COMT and MAO. Because it is not broken down it has a prolonged duration of activity. This drug has excellent absorption orally and penetrates the CNS.
- What are the actions of ephedrine?
- increases systolic and diastolic blood pressure
- causes bronchodilation
- mild stimulation of CNS causing increased alertness, decreased fatigue and prevents sleep
- improves athletic performance
* *ephedrine-containing herbal supplements were banned by FDA due to life-threatening CV reactions
- What are the uses of ephedrine?
- pressor agent during spinal anesthesia when hypotension occur
- myasthenia gravis as an adjuvant to cholinesterase inhibitors
- allergic disorders
- What is pseudoephedrine?
One of 4 ephedrine enantiomers that is available over the counter as a component of decongestant mixtures.
- What is phenoxybenzamine?
Phenoxybenzamine is a non-selective, irreversible, a-adrenergic antagonist. It was discovered to treat HTN, but was unsuccessful. It is currently used to treat PHEOCHROMOCYTOMA. It is given prior to surgical removal of the tumor and for chronic management of inoperable tumors.
- What is Phentolamine?
Phentolamine is a non-selective, reversible, a1 and a2 receptor antagonist. It is used…
- to treat pheochromocytoma by controlling HTN in preoperative prep and during surgical excision
- diagnose pheochromocytoma via phentolamine blocking test
- prevent dermal necrosis after extravasation of NE
- Hypertensive crisis due to stimulant drug overdose
- Cocaine-induced acute coronary syndrome to reverse coronary artery vasoconstriction
- Hypertensive crisis due to sudden withdrawal of sympatholytic antihypertensive drugs
- Hypertensive crisis due to interaction b/t MAOIs and tyramine and other sypathomimetic amines
- What is the epinephrine reversal?
All a-adrenergic blockers reverse the a-agonist effects of epinephrine. The vasoconstriction a1 action of epinephrine is blocked but vasodilation caused by activation of B2 is not blocked. Therefore, the systemic blood pressure decreases in response to epinephrine given in the presence of phenoxybenzamine (non-selective a blocker).
- What is the a1-blocker effect of the cardiovascular system?
1-blockers lower arterial blood pressure by relaxing both arterial and venous smooth muscle. The initial dose produces an exaggerated hypotensive response resulting in syncope (fainting). Therefore the initial dose must be 1/3 or 1/4th of the normal dose.
Prazosin is the main a1-blocker!