Cholinergic Receptors and Anticholinergic Drugs

Cholinergic Receptors and Drugs

• Types of cholinergic receptors:
  • Muscarinic receptors: stimulate smooth muscles and slow heart rate.
  • Nicotinic receptors: affect skeletal muscles.
• Types of cholinergic drugs:
  • Direct-acting: activate tissue response by acting on receptors.
  • Indirect-acting: inhibit cholinesterase, prolonging acetylcholine's action.
• Major effects of cholinergic drugs:
  • Increased bladder and GI tone.
  • Miosis (pupil constriction), reducing intraocular pressure.
  • Increased neuromuscular transmission.
  • Decreased heart rate and blood pressure.
  • Increased salivary and gastrointestinal secretions.

Anticholinergic Agents

• Action: Inhibit acetylcholine's action in the parasympathetic nervous system.
• Mechanism: Occupy acetylcholine receptors at parasympathetic nerve endings, preventing acetylcholine action.
• Affected organs: Heart, respiratory tract, GI tract, urinary bladder, eyes, and exocrine glands.
• Major responses:
  • Decreased GI motility.
  • Decreased salivation.
  • Mydriasis (pupil dilation) with increased intraocular pressure in glaucoma patients.
  • Increased heart rate.
  • Decreased sweating.

Drugs for Seizure Disorders

• Epilepsy: Abnormal electrical discharges from cerebral neurons, causing loss or disturbance of consciousness and often convulsions.
• Types:
  • Primary (idiopathic): 50% of cases, cause unknown.
  • Secondary: 50% of cases, caused by trauma, anoxia, infection, or stroke.
• International Classification of Seizures:
  • Generalized Seizures: Affect both brain hemispheres, accompanied by loss of consciousness, and may be convulsive or nonconvulsive.
    • Tonic-Clonic (Grand Mal): Most common form. Tonic phase (muscle contraction) lasts 3-5 seconds, followed by clonic phase (rhythmic muscle contractions).

Drugs for Pain Management

• Pain: Unpleasant sensory and emotional experience associated with actual or potential tissue damage.
• Pain Perception (Nociception): Awareness of pain sensation.
• Pain Threshold: Point at which a sensation is perceived as painful.
• Pain Tolerance: Ability to endure pain.
• Analgesics: Drugs that relieve pain without causing loss of consciousness or reflex activity.

Opiate Agonists

• Action: Relieve severe pain by stimulating opiate receptors in the CNS.
• Types:
  • Morphine and Morphine-Like Derivatives: Morphine
  • Meperidine-Like Derivatives: Fentanyl
  • Methadone-Like Derivatives: Methadone
  • Other Opiate Agonists: Tramadol
• Uses: Relieve acute or chronic moderate to severe pain.
• Special Precautions: Prolonged use can lead to tolerance and physical/psychological dependence.

Opiate Antagonists

• Naloxone (Narcan):
  • Action: Reverses CNS depressant effects of opiate agonists.
  • Uses: Treatment of respiratory depression from opiate overdose.
• Naltrexone:
  • Action: Long-acting pure opioid antagonist. Blocks opioid receptors, diminishing craving for opioids and alcohol.
  • Uses: Treatment of opioid addiction, alcohol dependence, and relapse prevention.

Salicylates

• Action: Inhibit prostaglandin formation, reducing pain, inflammation, and fever.
• Uses: Symptomatic relief of pain, inflammation, and fever associated with infections, headaches, muscle aches, and rheumatoid arthritis.
• Special Precautions: Not recommended for children due to the risk of Reye's syndrome.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

• Action: Inhibit prostaglandin synthesis by blocking cyclooxygenase (COX-1 and COX-2).
• Uses: Treat pain, inflammation, and fever similar to salicylates, but with different chemical structures.

Explore the intricacies of cholinergic receptors and drugs in this quiz. Learn about muscarinic and nicotinic receptors, their effects, and the role of anticholinergic agents in inhibiting acetylcholine action. Test your understanding of how these drugs affect various bodily functions.