Hello awesomites so here is my " Single page notes" on opioid analgesics.
Lets begin.
Let us know the difference between opiates and opioids.
Chemicals derived from opium or related to morphine chemically are called opiates.
And those having morphine like structures, irrespective of chemical action are called as opioids.
Opioid analgesics are classified as follow
1) Natural opium alkaloids
- Morphine, Codeine.
Morphine
A) Acts on Mu(Causes dependency-Euphoria) , kappa(Dysphoria - Psychomimetic) and delta receptors as agonist. Hence used as supraspinal and Spinal analgesic.
B) Treatment of poisoning: Naloxone 0.4-0.8 mg i.v. repeatedly for 2-3 minutes.
C) Can be administered through oral, rectal, i.m, i.v, intrathecal, epidural routes. Used as preanaesthetic medications
D) Useful in MI and acute pulmonary edema(Both by i.v. route)
E) Contraindicated in head injury, hypothyroidism patient, pregnancy.
Codeine.
A) Partial agonist at mu receptor.
B) 1/10th analgesic of morphine and less efficacious.
2)Semi-syntheic opioids :
Diacetyl morphine(Heroine), Pholcodine, Ethylmorphine.
Heroine:Three time more potent than morphine.
Codeine, pholcodeine, dextromethopran and noscapine are cough suppresants.
Dextromethopran is devoid of constipating action.
3) Synthetic opioids:
-Pethidine(Meperidine):
A) To control shivering after anesthesia
B) Used during labour as analgesic
C) Safer in asthma.
D) Pethidine and pentazosin both are anticholinergics. Hence they causes tachycardia. Perhaps, they are contraindicated in MI but useful in biliary colic
-Fentanyl:
A) Causes truncal rigidity due action on mu receptor.
B) Can be given as transdermal patch and as well as buccal transmucosal
-Methadone
A) Agonist action on mu receptor + blocks NMDA reuptake of monoamines and hence useful in neuropathic and cancer pain (Not controlled by morphine)
B) Can be given by oral, rectal, i.v, s.c, routes.
C) Long plasma half-life hence less dependency and tolerance. Therefore used as maintenance therapy in opioid dependency
-Dextropropoxyphene
A) At high doses it causes seizures.
-Tramadol
A) It is a weak mu receptor agonist and decrease reuptake of NA and 5-HT hence used as analgesia. This is abolished by Ondasteron.
By ojas
