Antagonism, Non-receptor antagonism | Non-selective Apha Blockers | Antiarrhythmic Drugs General, Vaughan Williams Classification

Question 1

Non-receptorial Antagonism

Answer 1

• Physiologic [Agonist to a receptor with opposite effect to receptor in target | Acetylcholine vs Epinephrine effects]
• Chemical [Drug that targets another drug and not the receptor | Protamine targeting Heparin]
• Pharmacokinetic [Drug that changes pharmacokinetic parameters akak LADME such that another drug’s effects are reduced | SSRIs and certain Beta blockers on CYP enzymes; Digoxin and Macrolides in elimination]
• Signal Transduction Inhibition [Lithium inhibits PIP2 synthesis]

Question 2

Non-selective Alpha blockers

Answer 2

Phentolamine [competitive, short acting]
Phenoxybenzamine [non-competitive irreversible, long acting]

Uses:
- HTN
- Pheochromocytoma