propranolol

non-selective beta-blocker

A non-selective $\beta$-blocker (Class II antiarrhythmic) distinguished by its high lipophilicity and unique non-cardiac indications.

• Mechanism:
  1. Non-selective $\beta$-antagonism ($$\begin{gathered} bet{a}_1, \\ bet{a}_2 \end{gathered}$$): Controls heart rate, tremor, and anxiety.
  2. Inhibits 5’-monodeiodinase: Blocks T4 $\to$ T3 conversion (high doses: $>160\text{ mg/day}$).
  3. Splanchnic Vasoconstriction: Reduces portal venous pressure ($bet{a}_2$ blockade).
• Dosing: Thyrotoxicosis: 10–40 mg PO q6h. Thyroid Storm: 60–80 mg PO q4h. Variceal Prophylaxis: Titrate to resting HR 55–60 bpm.
• PK: Highly lipid soluble (crosses BBB $\to$ treats anxiety/agitation, but causes nightmares). Short half-life (requires BID/QID dosing or ER formulation).

indications

• Hyperthyroidism / Thyroid Storm: Agent of choice. Blocks adrenergic drive and T4 conversion.
• Portal Hypertension: Prevention of variceal bleeding.
• Neurologic: Migraine prophylaxis, Essential tremor.
• Psychiatric: Performance anxiety, Akathisia.

cautions

• Asthma/COPD: High risk of bronchospasm due to $bet{a}_2$ blockade. Contraindicated in asthma.
• Diabetes: Masks hypoglycemia symptoms more profoundly than selective agents.
• Overdose: Highly toxic due to Na-channel blocking effects (wide QRS) + lipophilicity.

Class Overview: beta blockers