Pharm

Pyridostigmine

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Pyridostigmine, Pyridostigmine Bromide, Mestinon

  • Indications
  1. Pretreatment before Nerve Agent Exposure (Soman)
    1. Pyridostigmine does not protect against exposure
    2. Nerve Agent Exposures must be treated with Antidote (e.g. Pralidoxime chloride, Protopam chloride)
  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
  • Physiology
  1. Pyridostigmine is an Anticholinesterase
  2. Results in increased Cholinergic effects
  1. Pyridostigmine 30 mg PO every 8 hours before exposure
  2. Pharmacokinetics
    1. Significantly enhances post-exposure antidote for Soman
    2. Does not enhance antidote for other Nerve Agents
    3. Raises SomanLD50 by several fold
  • 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
      1. Doses exceeding 120 mg every 3 hours are not more effective
  3. Pharmacokinetics
    1. Onset: 15-30 minutes
    2. Peaks: 2 hours
    3. Duration: 3-4 hours
  4. Precautions
    1. Not often effective as monotherapy in Myasthenia Gravis
  • Adverse Effects
  1. Risk of worsening myasthenia crisis (due to mucous plugging, bronchorrhea)
  2. Risk of Cholinergic Toxicity (esp. at higher dose)
    1. Gastrointestinal side effects
    2. Muscle Fasciculations
    3. Eye tearing
  • References
  1. (1998) USAMRICD Chemical Casualties Handbook, p. 58-9