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Adjuvant analgesics rugs used to treat gout, centrally acting muscle…

- - - - Polyneuropathy
      - Traumatic nerve lesion
      - Spinal cord injury
      - Damage at the level of the middle brain, thalamus, cortex
    - - Phantom limb pain
      - Traumatic neuropathy
      - Postherpetic neuralgia
      - Trigeminal neuralgia
      - Pain following stroke
    - - Spontaneous pain
      - Mechanical heat or col hyperalgesia
      - Allodynia
- - - - Reduce the pathological tone of skeletal msucle w/o compromising voluntary contraction
      - Different then peripheral muscle relaxants
    - - Most drugs act in the spinal cord
      - Typical route of administration -> oral
      - Side effect
        
        sedation
        
        Muscle relaxants
      - clinical efficacy
        
        effective in spasticity only
        
        Effective in acute muscle spasm only
        
        Effective in both
      - Site of action
        
        presynaptic inhibition (GABA)
        
        Inhibition of excitatory transmitter from presynaptic neuron (baclofen)
  - - - Chronic, often only partially improving condition
      - Evoked by impairement of the descending corticospinal inhibitory pathways regulating stretch reflex
      - Spasm of antigravity muscles
      - enhanceed stretch reflex
      - pain and siability
    - - Reversible
      - Self improving condition
      - Muscle tone increase caused by reflex mechanism initiated by trauma or inflammation
        
        Affecting muscle or by pain
- - - - MOA
        
        Analog of hypoxanthine
        
        Act as substrate for xanthine oxidase
        
        Converted to oxipurinol
        
        Inhibit urate formation
        
        Non-competitive inhibitor of xanthine oxidase
      - T1/2
        
        Allopurinol 1h
        
        Oxipruinol 24h.
        
        Major part of allopruinol effect
        
        Excreted by urine
      - Effects
        
        Less uric acid is produced
        
        accumulate hypoxanthine and xanthine
        
        Have good water solubility
        
        slightly inhibit de novo purine synthesis
      - Side effect
        
        Increas risk of acute attack in the first 2 weeks
        
        Can be prevented by cochicines or NSAID
        
        GI disturbance
        
        Allergic reaction
        
        Renal failure
      - Interaction
        
        Slower metabolism
        
        Azathioprine
        
        Mercaptopurine
        
        Slower metabolism of coumarins/theophylline
        
        Xanthine oxidase inhibitor
    - - Reduce uric acid lvl
      - Recombinant urate osidase
        
        convert urate to allantoin which is awter soluble
  - - - Increase renal excretion of uric acid
        
        by inhibiting urate reabsorption in proximal tubule
      - MOA
        
        Given P.O
        
        Significant plasma protein binding
        
        Reach sight of action at luminal memb of proximal tubule
        
        Induce secretion of urate
      - Effect
        
        At lower dose
        
        Paradoxically evoke urate retention because they competitively inhibit active secretion of urate in proximal tubule
        
        Therapeutic dose
        
        The sum of these opposing effect is a net increase in renal excretion uric acid
      - Side effect
        
        increase risk of acute attack during the first 2 weeks
        
        Can be prevented by colchicines or NSAID
        
        Urate renal stone formation
        
        can be prevented by elevating pH of urine by NA-bicarbonate or NA-citrate
        
        Diarrhea
        
        Urate renal stone
  - - - MOA
        
        Inhibit polymerization of tubulin into microtubules
        
        Reduces chemotaxis and phagocytotic activity fo neutrophils and some function of T cells
      - Good oral absorption % I.v.
        
        used for 3-5 days only
      - Metabolism
        
        Partially by CYP3A4
        
        excreted in urine and bile by enterohepatic circulation
      - Side effect
    - - Drugs of choice because they have less side effect than cohicine
      - COX inhibitors with less GI side effect are used
    - - If the 2 other drugs don't work
- - - - Agonist of presynaptic GABA-b rec (Gi coupled)
      - MOA
        
        Reduces transmitter release from central terminals of type Ia proprioceptive afferent
        
        It is involved in the stretch reflex
        
        Inhibiton of the stretch reflex
        
        reduction of muscle tone
      - Orally or intrathecally
      - Metabolism
        
        unchanged by the kidney
      - Withdrawal
        
        Convulsion
        
        Hallucination
      - Flexor reflex is also inhibited
        
        by reducing transmitter release from central terminals of nociceptive afferents
    - - Under trial
  - - - I.m. or i.v.
      - inhibit polysynaptic spinal reflex
    - - inhibiting polysynaptic spinal reflex
      - may cause dizziness and cholestatic icterus
  - - - diazepam, Tetrazepam
        
        Anxiolytic action can contribute to therapeutic effect
        
        MOA
        
        Positive alloseric modulation of GABA-a rec
        
        Enhance presynaptic inhibitory effect of spinal GABA-ergic interneurons exerted on type Ia muscle afferent
        
        Reduce transmitter release
        
        inhibit stretch reflex
    - - Clonidine derivative
      - MOA
        
        alpha2 receptor agonist
        
        reduce transmitter release from central terminals of type Ia afferents
        
        Side effect
        
        Hypotension
        
        dry mouth
        
        Liver damage
    - - MOA
        
        Na channel block
        
        Inhibit propagation of action potential in muscle afferents
        
        Reduce transmitter release
        
        Inhibiton of the stretch reflex
      - Enhance peripheral blood flow
      - Orally or I.v.
      - Side effect
        
        hypotension
        
        Headache
        
        no sedation