**Core Concept**
Pyridostigmine and neostigmine are both cholinesterase inhibitors used in the treatment of myasthenia gravis, a neuromuscular disorder characterized by weakness and fatigue of skeletal muscles. These drugs work by inhibiting the enzyme acetylcholinesterase, thereby increasing the concentration and duration of action of acetylcholine, the neurotransmitter responsible for muscle contraction.

**Why the Correct Answer is Right**
Pyridostigmine is longer-acting compared to neostigmine due to its slower onset of action and longer duration of effect. This is because pyridostigmine has a higher lipid solubility, which allows it to penetrate the blood-brain barrier more slowly, but also allows it to persist for a longer period in the synaptic cleft, thereby providing a more sustained increase in acetylcholine levels. This property makes pyridostigmine particularly useful for patients with myasthenia gravis who require a longer duration of action.

**Why Each Wrong Option is Incorrect**
**Option A:** Pyridostigmine is not more potent than neostigmine; in fact, neostigmine has a faster onset of action but a shorter duration of effect.
**Option C:** While pyridostigmine may produce fewer muscarinic side effects due to its slower onset of action, this is not the primary reason it is different from neostigmine.
**Option D:** Pyridostigmine, like neostigmine, does have a direct action on the nicotinic receptors at the neuromuscular junction.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that pyridostigmine and neostigmine have different pharmacokinetic profiles, which affect their clinical utility. Pyridostigmine's longer duration of action makes it particularly useful for patients with myasthenia gravis who require a sustained increase in acetylcholine levels.

**Correct Answer:** B. It is longer acting