Pharmacology DOR 101

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Pharmacology DOR 101
Abdelkader Ashour, Ph.D. 3rd Lecture, contd.
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Muscarinic Agonists (Cholinomimetics,
Parasympathomimetics)

• ACh itself is rarely used clinically because of
  its rapid hydrolysis in the blood by
  pseudocholinesterase and at the cholinergic
  neurons by acetylcholinesterase
• There are also several other naturally occurring
  muscarinic agonists such as muscarine and
  pilocarpine which are resistant to hydrolysis
• Pilocarpine is commonly used for various purposes
  in ophthalmology. It is widely used to treat
  glaucoma, topically.
• Side effect of pilocarpine include
• increased sweating,
• asthma worsening,
• nausea,
• hypotension, and
• bradycardia (slow heart rate)

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Antichloinergic drugs

• Nonselective Muscarinic Antagonists
• The classical muscarinic antagonists are derived
  from plants and are nonselective competitive
  antagonists such as atropine
• Clinically, atropine is used for dilating the
  pupils (for eye examination)
• Its most widespread current use is in
  pre-anesthetic preparation of patients
• in this situation, atropine reduces respiratory
  tract secretions and thus facilitates intubation
• Ipratropium is used by inhalation as a
  bronchodilator

• Selective Muscarinic Antagonists
• Pirenzepine shows selectivity for the M1
  muscarinic receptor.
• Because of the importance of this receptor in
  mediating gastric acid release, M1 antagonists
  such as pirenzepine help patients with ulcer
  disease or gastric acid hyper-secretion

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Antichloinergic drugs, Atropine

• Side effects of muscarinic antagonists (such as
  atropine) include
• constipation,
• xerostomia (dry mouth),
• hypohidrosis (decreased sweating),
• mydriasis (dilated pupils),
• urinary retention,
• precipitation of glaucoma,
• decreased lacrimation,
• tachycardia