Final answer:
Neostigmine is likely to have a more profound effect on skeletal muscle than Physostigmine because it is more localized to the neuromuscular junction and does not penetrate the central nervous system as easily.
Step-by-step explanation:
When considering which drug has a greater effect on skeletal muscle, Physostigmine or Neostigmine, it is important to understand their mechanism of action. Both drugs inhibit the enzyme acetylcholinesterase, which is responsible for the breakdown of acetylcholine at the neuromuscular junction. The inhibition leads to an increase in acetylcholine, allowing it to continuously stimulate the muscle, potentially causing enhanced muscle contraction. However, neostigmine has a stronger association with skeletal muscle effects due to its poorer penetration through lipid membranes, thus having a more localized effect on the neuromuscular junction compared to physostigmine, which can cross the blood-brain barrier and is used for its central nervous system effects. Therefore, neostigmine is likely to have a more profound effect on skeletal muscle than physostigmine, making it particularly useful in the treatment of conditions like myasthenia gravis.