Pharm - Adrenergic Agonists and Antagonists Flashcards
What are the prototype non-competitive and competitive alpha adrenergic blockers?
Non-competitive = phenoxybenzamine
Competitive = phentolamine
Describe the mechanism of action for phenoxybenzamine (include receptor affinity, receptor binding, and metabolism)
Phenoxybenzamine preferentially binds alpha 1 over alpha 2 covalently. Can aldo bind H1, AChR, and serotonin receptors with high doses.
Half-time = 24 hours
Describe the pharmacologic effects of phenoxybenzamine on the CNS, cardiovascular system, eye, and penis
CNS - weakness, nausea, and vomiting
Cardiovascular - vasodilation through blocking alpha 1 and reflex tachycardia by blocking of presynaptic alpha 2 receptors near the heart
Eye - miosis
Penis - inhibition of ejaculation
What are the clinical uses (4) of phenoxybenzamine
- Pre-operative management of pheochromocytoma with propanolol or other beta blocker
- PVD
- Raynaud Syndrome
- Acrocyanosis
Describe the mechanism of action for phentolamine in reference to receptors bound
Phentolamine will bind alpha 1 and alpha 2 equally
Can also bind to H1 receptors in the gastric mucosa
Descirbe the effects of phentolamine on the cardiovascular system and GI tract
CV - causes vasodilation through alpha 1 and sometimes reflex tachycardia through the same mechanisms as phenoxybenzamine
GI - increases gastric motility and pepsin and HCl release
What are the clinical uses of phentolamine (3)?
- Surgical management of pheochromocytoma to prevent hypertensive crises
- Aid in withdrawal from clonidine
- Treat necrosis induced by local NE administration
What are the side effects phentolamine (4)?
- Nausea
- Vomiting
- Tachycardia
- Orthostatic hypotension
What type of adrenergic antagonists are ergot alkaloids from rye fungus?
Non-selective alpha blockers.
Some stimulation of serotonin receptors
What kind of antagonist is prazosin?
Selective alpha1 antagonist
What are the clinical uses and side effects of prazosin?
Used to treat hypertension, and does not cause relfex tachycardia
Syncope is the common side effect due to orthostatic hypotension
What type of drug is tamulosin?
Selective alpha 1A antagonist
What are the clinical uses and side effects of tamulosin?
This drug is specific for prostatic smooth muscle and is used to treat BPH
The specificity of the drug eliminates orthostatic hypotension
Describe the mechanism of action of propanolol
Non-selective competitive beta blocker
Note: this is a lipid soluble drug that is able to enter the CNS –> drowsiness
What are the effects of propanolol on the CV system, Respiratory system, and metabolism?
Cardiovascualr - decreases CO, HR, and AV nodal conduction and inhibits vasodilation.
Note: prolonged use can cause decreases in TPR
Respiratory - block bronchodilation
Note: avoid in asthmatics eedeot
Metabolism - block glycogenolysis and lipolysis
Describe the absorption and metabolism of propranolol?
This drug is absorbed orally, but variably susceptible to the first-pass effect. Each patient needs to be dosed individually
What are the cardiovascular uses (4) of propanolol?
- Hypertension
- Angina pectoris
- Arrhythmia
- Reduction of mortality after acute MI by decreasing the likelihood of ventricular arrhythmia and recurrent ischemia
What are the non-cardiovascular clinical uses (4) of propanolol?
- Management of preoperative pheochromocytoma along with phenoxybenzamine
- anxiety
- migraine headaches
- thyrotoxicosis - hyperthyroidism patients have lots of beta receptors
What are the common (6) and severe (6) side effects of propanolol use?
Common
- dizziness
- drowziness
- diarrhea
- depression
- constipation
- nausea
Severe
- fever
- rash
- purpura
- potentiate hypoglycemia
- increase VLDL and HDL
- interfere with SGOT and BUN assays
What are the four contraindications for propanolol use?
- Overt heart failure
- Cardiogenic shock
- Asthma
- AV nodal block
What is metoprolol and what is it used for?
Cardioselective Beta 1 antagonist used to treat hypertension
What is atenolol and what is it used for?
Cardioselective Beta 1 blocker used in the treatment of chronic stable angina and hypertension
Note: decreased risk of bronchospasm and does not prolong recovery from insulin-induced hypoglycemia
What is acebutolol and what is it used for?
A cardioselective beta blocker for hypertension and dysrrhythmias
What is betaxolol and what is it used for?
A beta 1 blocker for hypertension and glaucoma
What are the five catecholamines and describe there metabolism, distribution, and route of administration?
- Epinephrine
- Norepinephrine
- Isoproterenol
- Dopamine
- Dobutamine
These drugs are quickly metabolized, do not cross the BBB, and must be administered any other way than orally