Phentolamine / Regitine

Question 1

Drug Class (Pharmacologic and Therapeutic)

Answer 1

Pharm: Non-selective, competitive alpha-adrenergic receptor blocker
Therapeutic: antihypertensive drug for patients with pheochromocytoma

Question 2

Pharmacodynamics

Answer 2

Blocks alpha 1 and alpha 2 adrenergic receptors at presynaptic and postsynaptic alpha receptors, decreasing preload and afterload

Question 3

Pharmacokinetics

Answer 3

Only comes in IV formulation, so F=100%; plasma half-life about 20 min after IV dose

Question 4

Toxicity

Answer 4

Excessive hypotension with syncope, especially orthostatic, especially in patients on diuretics; allergic reactions; decreased libido

Question 5

Interactions

Answer 5

Additive effects with most other antihypertensives, especially diuretics

Question 6

Special Considerations

Answer 6

Rule out carcinoma of prostate before beginning treatment, do not crush or chew tablets, as that will speed up absorption; can also be used to treat spasm of ureter in patients with kidney stones

Question 7

Indications and dose / route

Answer 7

Aid in Dx of pheo; treatment of intra-op HTN during pheo removal surgery; prevention of dermal sloughing after extravasation of NE infusion; hypertensive crisis from sympathomimetic amines (discuss tyramine-MAO interaction) ; Dose 5 mg IV, then titrate, repeat as needed

Question 8

Monitor BP!!!

Answer 8

BP!!!