Rationale:

• Pyridostigmine pretreatment has only been shown to be effective against soman.
• To have any effect, pyridostigmine should be a taken at least 1 to 2 hours before soman exposure.
• Pyridostigmine bromide is a carbamate, which reversibly inhibits AChE, thereby leaving fewer receptor sites available for irreversible AChE inhibition by the nerve agent; as an inhibiter of AChE, pyridostigmine can cause mild cholinergic symptoms.
• Pyridostigmine prophylaxis is only effective if combined with appropriate postexposure treatment.

Evidence:

• In late 1990, the U.S. military fielded pyridostigmine bromide as a pretreatment for nerve agent exposure (6).
• A review article points out that pyridostigmine enhances the efficacy of postexposure treatment and permits survival at higher nerve agent challenges (7).
• In a randomized, placebo-controlled study with 90 patients, the dosage cited above was found to achieve blood plasma levels adequate to provide possible benefit in case of nerve agent exposure (8).

Comments:

• Note that pyridostigmine taken after exposure may worsen symptoms.
• Pyridostigmine is contraindicated in persons with mechanical intestinal or urinary obstruction. Caution is advised in persons with asthma and cardiac dysrhythmias.