Pyridostigmine

Aka: Pyridostigmine, Pyridostigmine Bromide, Mestinon

1. Indications
   1. Pretreatment before Nerve Agent Exposure (Soman)
   2. Myasthenia Gravis
      1. Provides symptomatic relief, esp. extremity weakness and bulbar symptoms
      2. Less effective on Ptosis and Diplopia
      3. Unlikely to benefit myasthenia crisis with Respiratory Failure and may interfere with respiratory management
2. Physiology
   1. Pyridostigmine is an Anticholinesterase
   2. Results in increased Cholinergic effects
3. Pharmacokinetics: Nerve Agent Exposure
   1. Significantly enhances post-exposure antidote for Soman
   2. Does not enhance antidote for other Nerve Agents
   3. Raises SomanLD50 by several fold
4. Dosing: Nerve Agent Exposure
   1. Pyridostigmine 30 mg PO every 8 hours before exposure
5. Dosing: Myasthena Gravis
   1. Child: 0.5 to 1 mg/kg every 4-6 hours (maximum 7 mg/kg/day divided every 4 to 6 hours)
   2. Adult
      1. Starting Dose: 30 mg three times daily
      2. Typical Dose: 60 to 90 mg every 4 to 6 hours while awake
      3. Maximum Dose: 120 mg every 4 hours while awake
   3. Pharmacokinetics
      1. Onset: 15-30 minutes
      2. Peaks: 2 hours
      3. Duration: 3-4 hours
6. Adverse Effects
   1. Risk of Cholinergic Toxicity
   2. Risk of worsening myasthenia crisis (due to mucous plugging, bronchorrhea)
7. Precautions: Nerve Agent Exposure
   1. Pyridostigmine does not protect against exposure
   2. Nerve Agent Exposures must be treated with Antidote
8. References
   1. (1998) USAMRICD Chemical Casualties Handbook, p. 58-9