Final answer:
Pyridostigmine and neostigmine can cause reduced gastric acid secretion and diarrhea.
Step-by-step explanation:
The drugs pyridostigmine and neostigmine are both used in the treatment of dysautonomia, a condition characterized by autonomic dysfunction. These drugs are acetylcholinesterase inhibitors, meaning they prevent the breakdown of acetylcholine, a neurotransmitter involved in autonomic functions. The primary effect of pyridostigmine and neostigmine is to increase parasympathetic activity, which can lead to various effects, including reduced gastric acid secretion (option E) and increased motility in the digestive system, potentially resulting in diarrhea (option C).