Muscarinic Antagonists

Parasympatholytics
Competitive Antagonists for Ach at Muscarinic receptors
1. Limited effect at the Neuromuscular junction or in Ganglionic transmission
  1. Nicotinic Receptors
    1. Sympathetic control
2. Similar structure to Ach, but bulkier aromatic group in place of Acetyl group
Synthetic
1. Glycopyrronium Bromide
  1. Does NOT cross placenta and BBB
    1. Less CNS effects; useful in caesarian sections
  2. Less tachycardias
  3. Used in ocular surgery to prevent Vagal Stimulation
2. Ipratopium Bromide
  1. Bronchodilation (horses)
    1. Tx for Chronic Obstructive Pulmonary Disease
  2. Given Inhalation: Poor absorption, poor distribution; minimal side effects, local effect in respiratory tract
3. Tropicamide
  1. Mydriatic
    1. Drug of choice: Intra-ocular exam
  2. Rapid onset, Shorter duration (hrs)
4. Cyclopentolate
  1. Mydriatic
  2. Cycloplegic
    1. Tx of Uveitis
  3. Long duration of action
Natural
1. Atropine
  1. Belladona (dilates pupils, toxic)
  2. Given I/M, I/V, S/C and P.O.
  3. Metabolized in Liver; Excreted by Kidneys
  4. Tertiary Amine; Ionized at physiological pH yet crosses the gut, conjunctival sac (eye), and BBB
  5. Premed - to decrease Salivation
  6. Antispasmodic effect in the gut; Decreases gastric secretion
    1. Not recommended in Horses
      1. Decreases GI motility, can cause central excitation
  7. Tx of organophosphorus toxicity
  8. Mydriasis - examination
  9. Increase HR
  10. Used with AChEI: to prevent side effects from Muscarinic stimulation when AChEI used to reverse neuromuscular blockade
  11. Toxicity
    1. CNS stimulation: Problem in horse
    2. Constipation
    3. Tachycardia
    4. Urinary retention
    5. AChEI can be used Tx Toxicity
      1. Increase Ach to compete w/ Atropine
2. Scopolamine (Hyoscine)
  1. Used for drying secretions
  2. Contained in Antispasmodic Buscopan (+ Dipyrone metamizole - analgesic)
    1. Decreases GI contractions
  3. Antiemetic properties

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Muscarinic Antagonists

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	Creado por melian.yates hace más de 10 años