Pharmacology Third Year

1. Opioid analgesics

2. Analgesics
• Drugs that relieve pain without loss of consciousness
►Opioid or narcotic analgesics (morphine type)
►Non-opioid or NSAIDs (aspirin type)

3. Opioids
Opium:
– white latex (exudate) obtained by incision of seed pod of Papaver
somniferum
Classification
• Naturally occurring: Morphine, Codeine
• Synthetic: Pethidine, Fentanyl, Methadone, Loperamide,
Opioid antagonists: Naloxone, Naltrexone.
Mixed agonist-antagonist: Pentazocine
Opioid Receptors: μ, Ќ, & δ
• μ: Supraspinal analgesia, Euphoria/Sedation, Respiratory depression,
Pupillary constriction,  GI motility.
• Ќ : Spinal analgesia/sedation
• δ: Spinal analgesia, opioid reinforcement & reward

4. Pharmacological actions of Morphine
Opioids act by stimulating the μ, Ќ, & δ receptors
• Miosis, decrease in pupil size
• Analgesia
• Respiratory depression
• Physical & psychological dependence
• Hypotension,
• Nausea and vomiting
• Cough suppression & constipation
• Sedation

5. Uses of Opioids
MORPHINE
Analgesic (Severe, sharp, visceral pain)
Myocardial Infarction, Burns, Fracture of long bones,
Cancer pain, Acute pulmonary oedema
PETHIDINE
Analgesic similar to Morphine
Epidural analgesia for Obstetric labour
METHADONE
De-addiction of Heroin /Morphine

6. Uses of Opioids
Other opioids:
• Codeine : Cough Suppression (Antitussive )
• Loperamide: Non infective diarrhoea
• Fentanyl + Droperidol: Neuroleptanalgesia
• Fentanyl + Droperidol + N2O: Neuroleptanesthesia
• Transdermal Fentanyl: Chronic neuropathic pain

7. Adverse effects of Morphine
1. Vomiting
2. Respiratory depression
3. Constipation
4. Itching and skin rash (histamine release)
5. Tolerance develops to most of the effects of morphine
except miosis & constipation.
6. Drug dependence ( physical & psychological )
Morphine poisoning:
• Known addict with needle marks, coma, pinpoint pupils,
depressed respiration, & constipation.
• Antidote- Intra venous Naloxone
• General supportive measures
•

8. Contraindications of Morphine
• Head injury
• Pregnancy
• Neonates & Elderly
• Dysentery in children
• Biliary colic
• Chronic obstructive pulmonary disease
• Hepatic & renal diseases.
• Hypothyroidism