1. Analgesics

2. Introduction
Analgesics are drugs that relieve pain due to multiple causes without affecting its cause.
Relieve pain by selective action in CNS or peripheral pain mechanism without producing unconciousness.
2 types –
NSAID
Opioids

3. NSAID

4. Classification Non selective COX inhibitors
Salicylic acid: Aspirin
Propionic acid derivative: Ibuprofen, Ketoprofen
Anthranilic acid derivative: Mefenemic acid
Aryl acetic acid derivative: Diclofenac
Oxicam derivatives: Piroxicam, Tenoxicam
Pyrrolo-pyrrole derivatives: Ketorolac
Indole derivative: Indomethacin
Pyrrazolone derivative: Phenylbutazone
Preferential COX2 inhibitors:
Nimesulide, Meloxicam

5. IV. Analgesic-antipyretic with poor anti- inflammatory action:
III. Selective COX2 inhibitors:
Celecoxib, Rofecoxib, Valdecoxib
IV. Analgesic-antipyretic with poor anti- inflammatory action:
Paraamino phenol derivative: Paracetamol
Pyrrazolone derivative: Propiphenazone
Benzoxazocine derivative: Mefopam

6. Mechanism of action
These drugs inhibit the synthesis of prostaglandins.
Phospholipids are converted to arachidonic acid by phospholipase A. Arachidonic acid is then converted to prostaglandin by COX enzyme.
NSAID inhibit COX enzyme.

7. Therapeutic actions Analgesia Anti-pyresis Anti-inflammatory
Patency of ductus arteriosus
Primary dysmenorrhoea

8. Side effects
Gastrointestinal side effects: Dyspepsia, nausea, vomiting, diarrhoea or constipation
Disturbance in platelet function
Inhibition of uterine motility leading to prolongation of gestation period
Can cause intrauterine closure of ductus arteriosus in infants
Increased risk of post partum haemorrhage
Analgesic nephropathy

9. Opioids

10. Classification
Pure agonists: high affinity for mu receptors and varying affinity for delta and kappa receptors; lack appreciable activity at sigma receptors
Total opium alkaloids: Omnapon
Purified opium alkaloids: Morphine, Codeine
Synthetic analogues of morphine: Heroin, Levorphenol
Synthetic analogues of codeine: dihydrocodeine, Tramadol
Morphine substitutes:
Meperidine and its analogues: Meperidine, fentanyl, Sufentanyl, Alfentanyl, Ramifentanyl, Diphenoxylate, Loperamide
Methadon and its analogues: Methadon, Levomethadyl acetate, Dextropropoxyphene

11. II. Partial agonist and mixed agonist- antagonist:
Pentazocin, Nalbuphine, Butorphenol, Buprenorphine, Meptazinol, Dezocine
III. Pure antagonist:
Naloxone, Neltrexone

12. Mode of action
Endogenous opioid peptides (encephalins, dynorphins, endorphins) are attached to specifc opioid receptors.
Three opioid receptors are mu, kappa and delta.
Opioids act on these receptors to produce effects

13. Indications
As analgesic in MI,biliary cholic, post operative pain, obstetrical analgesia
Sedation
Diarrhoea
As pre-anaesthetic medication and as balance anaesthesia
Cough
Dyspnoea in acute left ventricular failure

14. Contraindications Head injury Increased intracranial pressure
Hypotension and haemorrhage
Bronchial asthma
Myxoedema, multiple sclerosis & Addison’s disease
Grossly impaired liver and kidney function
In presence of convulsive diseases
Biliary cholic
Benign prostatic hypertrophy

15. Adverse effects
Behavioural: anxiety, confusion, dysphoria, restlessness
Nausea, vomiting
Increased biliary pressure
Urinary retention
Hypersensitive reaction: itching around nose and urticaria by i.v. routes
Postural hypotension, increased intracranial pressure, respiratory depression