A 45-year-old woman with myasthenia gravis is switched from neostigmine to pyridostigmine for long-term therapy. Pyridostigmine is preferred for chronic use because it has:
- A A longer duration of action and smoother clinical effect ✓
- B Greater nicotinic selectivity and fewer muscarinic side effects
- C Oral bioavailability close to 100 percent with no GI side effects
- D No central nervous system penetration and no CNS toxicity
Correct answer: A. A longer duration of action and smoother clinical effect
Explanation
Pyridostigmine has a longer duration of action (3 to 6 hours) compared to neostigmine (2 to 4 hours), producing a smoother clinical effect suitable for chronic myasthenia gravis management. Both are quaternary ammonium compounds with similar nicotinic and muscarinic profiles and poor CNS penetration. Neither has 100 percent oral bioavailability (pyridostigmine is approximately 10 to 20 percent). The drugs are pharmacologically similar; the key practical difference is duration.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.