1 / 31

Analgesic drugs

Analgesic drugs. MBChB: Y2. This talk. Pain: classification Brief resume of common arthritides Paracetamol NSAIDs Drugs for gout Not covered: Opiates, ‘disease modifying drugs for rheumatoid, drugs for neurogenic pain. Pain. Somatic inflammation of epithelial surfaces, trauma, sepsis

guido
Download Presentation

Analgesic drugs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Analgesic drugs MBChB: Y2

  2. This talk • Pain: classification • Brief resume of common arthritides • Paracetamol • NSAIDs • Drugs for gout • Not covered: • Opiates, ‘disease modifying drugs for rheumatoid, drugs for neurogenic pain.

  3. Pain • Somatic • inflammation of epithelial surfaces, trauma, sepsis • felt at site of pathology • Visceral • e.g. myocardial ischaemia, colic • poor localisation, often ‘referred’ • Neurogenic • e.g. neuralgia • no response to analgesics

  4. Osteoarthritis • Common • A disease of cartilage • Big weight-bearing joints: knees and hips • More likely if there is joint insult (e.g. trauma) • Congenital component: ‘primary familial osteoartritis’

  5. Heberden’s nodes

  6. Rheumatoid arthritis • Common • May commence at any age • Inflammatory condition: joints are the commonest ‘tissues’ involved, but rheumatoid also inflames arteries etc. • Small joints: hands and feet • Hands: the MCPJs and the PIPJs

  7. Gout • Common • A PAROXYSMAL arthritis, with quiet joints between attacks. • Any joint, excepting the axial skeleton. • Most commonly the first MTPJ • Uric acid crystals in joint fluid

  8. Ankylosing spondylitis • Less common • About 20% of people with HLA B27 • Low back pain in the early 20s, leading to variable degrees of spinal deformity. • Arthritis also of hips and knees • Other tissues: iritis

  9. Drugs

  10. Paracetamol • Mechanism of analgesic activity not fully understood: ?  prostaglandin synthesis in the CNS • Mechanism of antipyretic activity:  PG-E2 in the hypothalamus

  11. Paracetamol • Safe effective analgesic used OTC • analgesia • lowering elevated temperature • it has no anti-inflammatory effect

  12. Dangerous in overdose

  13. Dangerous in overdose saturated

  14. Dangerous in overdose The main problem is hepatotoxicity Takes around 24-36 h to become apparent saturated Antidote: n-acetyl cycteine But use in the first 24 h Damage correlates with paracetamol conc. Measure conc. No earlier than 4 h

  15. NSAIDs

  16. Phospholipase A2 Arachidonic acid COX-I COX-II Leukotrienes PGs with gastric protective effects PGs with inflammatory effects Membrane phospholipid

  17. steroids X Membrane phospholipid Phospholipase A2 Arachidonic acid COX-I COX-II Leukotrienes PGs with gastric protective effects PGs with inflammatory effects

  18. steroids X Membrane phospholipid Phospholipase A2 Older NSAIDs Arachidonic acid X X COX-I COX-II Leukotrienes PGs with gastric protective effects PGs with inflammatory effects

  19. steroids X Membrane phospholipid Phospholipase A2 Arachidonic acid COX-II inh X COX-I COX-II Leukotrienes PGs with gastric protective effects PGs with inflammatory effects

  20. Aspirin • Acetylsalicylic acid • Analgesic/antipyretic at low dose • Anti-inflammatory at high dose • (Anti-platelet activity at low dose) • Upper GI irritation and bleeding

  21. Aspirin Overdose • Partly eliminated unchanged in the urine. • Aspirin is a strong acid, and is lipid soluble at acid pH (remember Henderson Hasselbach). • ‘Alkaline diuresis’: iv bicarbonate to yield alkaline urine. • Hence water soluble aspirin and higher aspirin clearance. • Dialysis in the most serious cases.

  22. Other NSAIDs • (Ibuprofen: OTC as an analgesic) • Naproxen • Diclofenac • Useful in inflammatory arthritis • Useful adjunct to opiates in terminal care

  23. COX-II inhibitors • Anti-inflammatory, useful for Rh-D • Much more expensive than older NSAIDs • Reserve for selected patients with PUD or GORD. • Rofecoxib withdrawn for SAEs. This may prove to be a class effect.

  24. NSAID adverse effects • GI • Salt and water retention • Renal impairment • Asthma may be precipitated

  25. Drugs for gout.

  26. Acute gout. • Paroxysmal arthritis. Any joint (other than the axial skeleton) but 1st MTPJ is the commonest. • Commonly precipitated by diuretics (esp thiazides). • May be very severe and resemble septic arthritis. • Joint aspirate: uric acid crystals.

  27. Treating acute gout. • Rest. • NSAID until arthritis settles. • Worst cases merit prednisolone. • If prophylactic drug, such as allopurinol, is to be used then NSAID ‘cover’.

  28. Allopurinol • Purine bases metabolised via xanthines to uric acid. • Xanthines are water soluble. • Uric acid is pretty insoluble. • Allopurinol inhibits xanthine oxidase. • Used to reduce frequency of paroxysms. • May precipitate acute gout when first started: NSAID ‘cover’.

  29. Allopurinol ADRs and interactions • GI upset • Rash • Azathioprine - potentiated. • Warfarin - potentiated.

More Related