Thoughts from the operating room, the laboratory, and the spaces in between — on medicine, science, and the human condition. Short entries; occasionally a figure or a link worth sharing.
A comparison of the two main alpha-blockers used in preoperative preparation for pheochromocytoma.
| Feature | Doxazosin | Phenoxybenzamine |
|---|---|---|
| Class | Selective α1-adrenergic antagonist | Non-selective irreversible α1 and α2 adrenergic antagonist |
| Receptor Selectivity | Selective for α1 receptors | Non-selective (blocks both α1 and α2 receptors) |
| Mechanism of Action | Blocks α1 receptors, leading to vasodilation and decreased blood pressure | Irreversibly blocks α1 and α2 receptors, leading to prolonged vasodilation and decreased blood pressure |
| Duration of Action | Intermediate (12–24 hours) | Long-lasting (24–48 hours or more due to irreversible binding) |
| Half-Life | ~22 hours | 24 hours, but effects can last longer due to irreversible binding |
| Onset of Action | 1–2 hours | Slower onset, hours to days |
| Clinical Effects | Decreases blood pressure via vasodilation, less reflex tachycardia | Prolonged and sustained blood pressure control, higher reflex tachycardia due to α2 blockade |
| Side Effects | Dizziness, hypotension, mild reflex tachycardia | Orthostatic hypotension, tachycardia, nasal congestion, fatigue |
| Adrenergic Receptor | Location | Effects of Receptor Agonism | Receptor Agonists | Receptor Antagonists |
|---|---|---|---|---|
| Alpha-1 (α1) | Vascular smooth muscle, eyes, bladder, prostate | Vasoconstriction, pupil dilation (mydriasis), bladder contraction, increased peripheral resistance | Phenylephrine, Norepinephrine | Prazosin, Doxazosin, Terazosin |
| Alpha-2 (α2) | Presynaptic nerve terminals, pancreas, platelets | Decreased norepinephrine release, decreased insulin release, platelet aggregation | Clonidine, Methyldopa | Yohimbine, Phentolamine |
| Beta-1 (β1) | Heart (SA node, AV node), kidneys | Increased heart rate, increased contractility, increased renin release | Dobutamine, Isoproterenol, Epinephrine | Metoprolol, Atenolol, Bisoprolol |
| Beta-2 (β2) | Bronchial smooth muscle, skeletal muscle vessels, liver, uterus | Bronchodilation, vasodilation, glycogenolysis, uterine relaxation | Albuterol, Terbutaline, Salmeterol | Propranolol, Labetalol |
| Beta-3 (β3) | Adipose tissue, bladder | Lipolysis, bladder relaxation (detrusor muscle) | Mirabegron | N/A |
Variant adrenal vein anatomy occurs in 13% of laparoscopic adrenalectomies.
RLN reconstruction test question. Further reading:
Preoperative Lugol's solution for Graves': decreases vascularity and blood loss; may decrease hypoparathyroidism and nerve injury rates.
Neoadjuvant selective RET inhibitor (selpercatinib) for medullary thyroid cancer:
Japanese approach to MTC allows for lobectomy (with central and lateral dissection) for patients with sporadic non-RET disease:
RLN monitoring studies: