PHARM PNS IV Flashcards
What are the mechanisms of action of Phenylpropanolamine?
- direct –> a-1 receptor agonist
- indirect –> increase in norepinephrine in bladder neck/urethra
- used to treat urinary incontinence
What are some indications of Phenylpropanolamine?
- used in small animals (dogs) to treat urinary incontinece due to urethral sphincter hypotenuse/incompetence
What is a drug to drug interactions with Phenylproanolamine?
Estrogens can up regulate a-1 receptors in internal urethral sphincter so may see synergisms
What are some precautions for Phenylproanolamine?
- urinary retention
- tachycardia
- hypertension
- restlessness
- occasionally anorexia
- few side effects at therapeutic doses
What are some mechanisms of action of Ephedrine?
- direct –> a-1 and B receptors (mostly B-1) agonist
- indirect –> increase in norepinephrine release (primary mechanism of action)
What are some precautions with Ephedrine?
- hypertension
- arrhythmias (less common than with catecholamines)
What are some indications and main effects of Ephedrine?
- used as CRI to maintain blood pressure under anesthesia (vasopressor effect)
- increase blood pressure –> vasoconstriction and direct cardiac stimulation
- bronchodilator (same B-2 effects)
- urinary sphincter contraction may cause urinary retention
- mydriasis
What are some indications of Vasopressin?
- vasopressor agent
- used in adjunct treatment of shock syndromes and cardiopulmonary cerebral resuscitation (CPR or CPCR) –> no evidence its better than epinephrine
- treatment of central diabetes insipidus (CDI) but Desmopressin is better for this
- treatment of Von Willebrand Factor deficiency like Desmopressin
What are some precautions and adverse effects of Vasopressin?
- GI signs like nausea and cramping
- extravasation injury and local irritation and injection site (including sterile abscess)
- water retention (hypovolemia can occur) –> overdoes can lead to water intoxication
What are some contraindications to Vasopressin?
Chronic nephritis with uncontrolled azotemia
What are mechanisms of action of Phenoxybenzamine?
- none specific alpha antagonist (a-1 and a-2)
- noncompetitive (irreversible antagonist that lasts about 3-4 days
What are some precautions of Phenoxybenzamine?
- excessive a-blockade which can cause hypotension, reflex tachycardia, mitosis and change in intraocular pressure, GI signs and its expensive AF
What are some indications of Phenoxybenzamine?
- used to treat urinary retention due to urethral hypertonicity by relaxing internal sphincter and may be combined with other stuff like diazepam
- pheochromocytoma (malignant tumor of the adrenal glands) –> prior to surgery treat associated hypertension for a better outcome
What is the main difference between Prazosin and Phenoxybenzamine?
Prazosin is more specific to the a-1 receptor and it may cause less hypotension
Which drugs are DIRECT ACTING ALPHA ANTAGONISTS that are sympathoLYTIC?
Phenoxybenzamine and Prazosin (and Phentolamine but this is an FYI)
