Pyridostigmine is an acetylcholinesterase inhibitor which means that it decreases the degradation of the neurotransmitter acetylcholine. Acetylcholine is used in both the sympathetic and parasympathetic nervous systems, but is more prevalent in the parasympathetic nervous system. Because of this, it was hypothesized that pyridostigmine would increase parasympathetic nervous system activity and therefore decrease heart rate in POTS.
Patients wtih POTS were given 30 mg pyridostigmine and placebo on different mornings. Compared to placebo, pyridostigmine: