Adrenergic Drugs Flashcards
What happens to noradrenaline after it has been released?
The majority of it is taken up again by the Uptake 1 protein, back into the pre-synaptic cleft.
The rest of it is then taken up by the Uptake 2 protein - Uptake 1 has a higher affinity than Uptake 2.
It can then be recycled and put back into vesicles, or it can be metabolised by the enzyme MAO.
How do alpha-methyl-tyrosine drugs work, and what are they used to treat?
They work by competitively inhibiting the rate-limiting enzyme tyrosine hydroxylase.
This blocks the conversion from tyrosine, preventing the formation of noradrenaline.
This is used to treat pheochromacytoma.
How does the drug alpha-methyl-DOPA work, and what is it used to treat?
They work by being converted into a molecule, by DOPA carboxylase, that accumulates in synaptic vesicles.
Once released, it activates the pre-synaptic alpha2-adrenoceptors, reducing the release of neurotransmitters.
It is used to treat hypertension.
How does carbiDOPA work, and what is it used to treat?
It inhibits DOPA decarboxylase in the periphery, not CNS as it doesn’t cross the blood-brain-barrier.
It is used to treat Parkinson’s.
What is an indirectly-acting sympathomimetic agent (IASA), and give an example?
They are structurally-related to adrenaline and so act as weak agonists.
They are re-uptake by Uptake I and cause noradrenaline to leak from the vesicle, into the synaptic cleft, increasing the concentration of NA there.
An example is amphetamine.
What are Uptake I inhibitors, an example of them, and what are the side-effects?
They are drugs that prevent noradrenaline from being taken up from the synaptic cleft.
This increases the concentrations of noradrenaline in the synaptic cleft, which can be used to treat depression.
Amitriptyline.
They enhance sympathetic actions - increase heart rate, and contractility, and can cause arrhythmias.
What are beta1-agonists, their uses, and what is an example?
It is a drug that can increase the rate and force of contraction of the heart.
This can be good for treating circulatory shock.
Dobutamine.
What are beta2-agonists, their use, and what is an example?
They cause bronchodilation.
An example is salbutamol.
What is an alpha1-agonist used for and what is an example?
It is used as a nasal decongestant.
Phenylephrine, or oxymetazoline.
NOTE: it can be used along side an anaesthetic to cause local vasoconstriction and prolong the anaesthetic affect.
What is an alpha2-agonist, it’s use and an example?
It is a drug that activates the alpha2 adrenoceptor, found on pre-synaptic neurones. This decreases the release of noradrenaline.
It can be used as an anti-hypertensive.
An example is clonidine.
What is an alpha-adrenoceptor antagonist used to treat, but why are they not really used?
They inhibit alpha-adrenoceptors and so stimulate vasodilation of the peripheries, treating peripheral vascular disease.
They are not used, however, as they cause postural hypotension and tachycardia (as a result).
What is the alphabetical tip used to determine the action of a beta blocker?
If it starts with the letter A-M then it is beta1 selective, if it is after M, then it is not selective.
Not selective means that it acts on beta1 and 2 (and 3) adrenoceptors, and so has more side effects.
What is a selective alpha1-adrenoceptor antagonist used to treat, and what is an example of this? Are they any drawbacks?
This is used to treat hypertension by inhibiting vasoconstriction.
An example of this is prazosin.
Despite is being specific, it can cause excessive vasodilation, leading to postural hypotension and impotence.
What is a beta-adrenoceptor antagonist used for, an example, and why it isn’t often used?
It is used to treat hypertension, heart failure, angina, myocardial infarction and cardiac arrhythmias.
An example is propranolol.
It isn’t often used as it isn’t specific and so it acts on both beta1- and beta2-adrenoceptors.
By inhibiting beta2-adrenoceptors, it can cause bronchoconstriction.
By inhibiting beta1-adrenoceptors, it can cause bradycardia, cold extremities, insomnia and depression.
Outline the basic steps in neurotransmission.
