chap 5

• Cholinergic antagonist


  Also called cholinoceptor antagonist, they have the ability to bind to the receptors of acetylcholine, either muscarinic or nicotinic receptors, and prevent the binding of acetylcholine and other agonists
• Cholinoceptor antagonists


  • They only have the ability to bind to the receptor with high affinity but they don't have intrinsic activity, they are not capable of activating the receptors
• Muscarinic receptor blocking drugs

  Also called anticholinergic agents or parasympathetic antagonists, they specifically antagonise the muscarinic receptors
• Muscarinic receptor antagonists


  • Atropine
  • Hyoscyamine
• Atropine


  The prototype muscarinic receptor antagonist, also called hyoscyamine, derived from plants like Atropa belladonna, Datura stramonium, and Datura metel
• Mechanism of action of atropine

  Binds to and blocks muscarinic receptors, thereby preventing the effects of acetylcholine and other cholinergic agonists
• Effects of atropine


  • Dilates pupils (mydriasis)
  • Causes cycloplegia (loss of accommodation)
  • Reduces lacrimation (dry eyes)
  • Reduces gastrointestinal secretions and motility (dry mouth, prolonged gastric emptying)
  • Increases heart rate (at low doses)
  • Causes bronchodilation
  • Causes urinary retention
• Anticholinergic drugs


  Also called antispasmodic drugs, they can be used to treat conditions involving smooth muscle spasms, e.g. intestinal spasms
• Anticholinergic antispasmodic drugs


  • Atropine
  • Hyoscine and butylbromide (Buscopan)
• Atropine and Buscopan (hyoscine and butylbromide) are used to treat smooth muscle spasms
• Atropine can have adverse effects like intestinal paralysis if overdosed
• Irregular menstruation


  Can be caused by hormonal imbalance, often improved by diet and exercise to normalise hormones
• Calculating fertile days using menstrual cycle

  1. Shortest cycle minus 18 days = start of fertile period

  2. Longest cycle minus 11 days = end of fertile period
• Depo-Provera is a contraceptive injection containing a hormone that can affect menstrual cycles
• Loperamide


  An anticholinergic drug used to treat diarrhea, a combination of loperamide and atropine
• Atropine can have dose-dependent effects on the cardiovascular system, causing bradycardia at low doses and tachycardia at high doses
• Atropine causes bronchodilation, which is useful for asthma and COPD patients
• Atropine can cause urinary retention, which can be beneficial for patients with urinary incontinence
• Atropine can reduce sweating, but should be used cautiously in infants due to risk of fever
• Bradycardia


  Slow heart rate
• Bronchoconstriction


  Narrowing of the airways
• Bronchodilation


  Widening of the airways
• Atropine and other anticholinergics cause bronchodilation, which is a useful effect for patients with asthma and COPD
• Urinary retention


  Inability to urinate
• Urinary incontinence


  Involuntary voiding
• Atropine can cause urinary retention, which is beneficial, but not for patients with hyperhidrosis (excessive sweating)
• Atropine is not effective for treating hyperhidrosis because the apocrine glands, not the eccrine glands, are responsible for excessive sweating
• Atropine at normal doses causes stimulation of the central nervous system, which is why it is a prescription drug
• Atropine at higher doses has a slower, longer-lasting sedative effect on the central nervous system
• Atropine


  • It is a mydriatic drug (dilates the pupils)
  • It is a cycloplegic agent (weakens the muscles of accommodation in the eye, causing loss of near vision)
• Atropine


  • It has antispasmodic effects, relaxing smooth muscles in the gastrointestinal tract
  • It can increase heart rate (tachycardia) at high doses
• Atropine is included in emergency kits in hospitals, but is highly monitored by pharmacists
• Atropine is used for treating cholinergic agonist poisoning, such as from organophosphate insecticides
• Adverse effects of atropine

  • Blurred vision
  • Dry mouth
  • Tachycardia
  • Urinary retention
  • Constipation
  • Restlessness
  • Confusion
  • Memory loss
  • Hallucinations
  • Respiratory and cardiovascular collapse
• Atropine is contraindicated in people with prostatic hyperplasia (enlarged prostate)
• Scopolamine


  Also known as hyoscine, it is another anticholinergic alkaloid
• Scopolamine


  • Has greater effects on the central nervous system compared to atropine
  • Is very effective as an anti-motion sickness drug
  • Can cause sedation and short-term memory impairment
• Ipratropium


  A synthetic anticholinergic drug used for asthma and COPD
• Ipratropium is the only anticholinergic drug used for asthma and COPD
• Tiotropium


  A newer once-daily anticholinergic drug for asthma and COPD