Adrenoceptor Antagonists Flashcards
What inhibits Tyrosine hydroxylase?
Metyrosine; Used in adrenal medullary tumor.
What inhibits aromatic L-amino acid decarboxylase?
Carbidopa; Inhibits metabolism of levodopa to Dopamine in the periphery
Discuss Phenoxybenzamine
Reactive intermediate binds (irreversibly) covalently to alpha-adrenoceptors; Inhibits reuptake of NE. Used to treat adrenal medullary tumor.
What are the side effects of Phenoxybenzamine?
- Decreased peripheral vascular resistance and blood pressure
- Increased release of NE from nerve terminals.
- Dry mouth
- Postural hypotension
What are the symptoms of pheochromocytoma?
- Hypertension
- Increased sweating
- Palpitations
- Headaches
Discuss Phenolamine
Reversible antagonist, Used for BP control in pheochromocytoma patients, Hypertensive crisis after abrupt clonidine withdrawal. A1=A2
What are the side effects of Phenolamine?
Hypotension, abdominal pain
Discuss Prazosin
Reversible antagonist. Decreases peripheral vascular resistance and venous return. Can cause hypotension; A1>A2
Discuss Terazosin
More water soluble, longer duration of action with higher bioavailabilty compared to Prazosin. Treats BPH and hypertension
Discuss Tamsulosin
Has a greater potency to prevent contraction of prostate compared to vasculare smooth muscle. Effective in treating BPH
Discuss Yohimbine
Treats orthostatic hypotension. Can reverse antihypertensive effects of an A2-adrenoceptor.
Side effects: Tremor and anxiety
What drug is used for Pheochromocytoma? Chronic hypertension? Reynaud’s? BPH?
Pheochromocytoma: Phenoxybezamine
Chronic hypertension: Terazosin, Doxazosin
Reynaud’s: Prazosin
BPH: Terazosin, Doxazosin
