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Prof Graeme Henderson Department of Pharmacology C32 Medical Sciences Building

Prof Graeme Henderson Department of Pharmacology C32 Medical Sciences Building graeme.henderson@bris.ac.uk Anticholinergics Opioids Benzodiazepines and related agents Issues multiple agents and ‘me too drugs’ receptor selectivity ‘natural’ products and synthetic agents

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Prof Graeme Henderson Department of Pharmacology C32 Medical Sciences Building

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  1. Prof Graeme Henderson • Department of Pharmacology • C32 Medical Sciences Building • graeme.henderson@bris.ac.uk • Anticholinergics • Opioids • Benzodiazepines and related agents • Issues • multiple agents and ‘me too drugs’ • receptor selectivity • ‘natural’ products and synthetic agents • pharmacokinetics

  2. Anticholinergic drugs/cholinergic antagonists Muscarinic antagonists (not nicotinic antagonists) Muscarinic receptor subtypes M1 – CNS M2 – heart M3 – smooth muscle and secretory glands M4 & M5 Most current drugs are not selective e.g. atropine pirenzepine M1/M3 benztropine M1 (less peripheral side effects)

  3. Muscarinic antagonists Tertiary amines (CNS penetrant) atropine, scopolamine, benztropine, procyclidine Quaternary amines (not CNS penetrant) propantheline, ipratropium, dicyclomine (low absorption into blood stream after oral administration – use in GI spasticity disorders)

  4. Use of muscarinic antagonists Smooth muscle relaxation(GI disorders -IBS) bronchodilation (exercise induced asthma, obstructive pulmonary disease) decrease secretions in surgery Parkinson’s disease

  5. Drugs exhibiting anticholinergic side effects tricyclic antidepressants (less with SSRIs) antipsychotics antihistamines (sedating) dopaminergics (e.g. amantidine)

  6. Side effects of anticholinergics Constipation Transient bradycardia followed by tachycardia and increased BP Palpitations and arrythmias Decreased bronchial secretions Dry mouth and thirst Blurred vision, pupilary dilation, loss of accommodation Urinary urgency and retention Photophobia Confusion (elderly) Nausea and vomitting Giddiness

  7. Opioid analgesics Receptors mdk ORL1 (MOR) (DOR) (KOR) (NOR) euphoria dysphoria Partial agonist at m receptor – buprenorphine Mixed agonist and antagonist – k agonist and m antagonist (pentazocine)

  8. Major therapeutic effects Analgesia Sedation Euphoria Antitussive Constipation Unwanted effects Euphoria Constipation Nausea and vomitting Respiratory depression Decreased gastric acid secretion Histamine release (itch) Raised intracranial pressure hypotension Other effects Miosis – pin point pupils(no tolerance)

  9. Contentious issues in pain therapy • Is the patient receiving adequate pain relief? • choice of drug, dose of drug • Does tolerance occur? • Does psychological dependence occur (craving)? • Does physical dependence occur? • Is respiration depressed?

  10. Individual agents (>20 listed in BNF) Powerful agonists Morphine Heroin Fentanyl Tramadol Partial agonist Buprenorphine (bell shaped response curve) Weak agonists Codeine Pethidine Pentazocine Dextropopoxyphene Anti diarrhoeal Diphenoxylate (low CNS penetration) Antitussive Dextromethorphan Treatment of opioid dependence Methadone (orally active, long t1/2) Antagonist Naloxone (short t1/2) Naltrexone

  11. Antianxiety, sedative and hypnotic agents BenzodiazepinesBZ receptor agonists Zopiclone/zolpidemBZ receptor agonists Buspirone5HT1A receptor agonist

  12. Role of pharmacokinetics in choice of drug Hypnotic Short t1/2 - temazepam, nitrazepam, zopiclone Antianxiety Long t1/2 - chlordiazepoxide, lorazepam, diazepam

  13. Benzodiazepines • Clinical Uses • anti anxiety • sedative • hypnotic • anticonvulsant • muscle relaxant • Side effects • drowsiness • confusion • amnesia • impaired motor coordination • lack of depth perception • reduced REM sleep

  14. Benzodiazepines Tolerance greater to anxiolytic and anticonvulsant actions than to hypnotic actions Physical dependence withdrawal induces anxiety dizziness tremor sleep disturbances No Psychological dependence

  15. Buspirone • long t1/2 • Side effects (less than with benzodiazepines) • nausea • dizziness • headache • restlessness • No reports of tolerance and physical dependence

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