Pharmacology 2: Morphine Adverse Effects

Morphine Adverse Effects

• Morphine decreases respiration and induces bronchospasm
• Causes miosis, a pinpoint pupil
• Leads to nausea and vomiting
• Induces hypotension and bradycardia
• Causes constipation and retention of urine
• May cause neonatal asphyxia
• Can cause itching and physical dependence
• Tolerance develops to all effects except constipation and miosis, and shows cross-tolerance with other opioids
• Interferes with proper diagnosis of head injury and acute abdomen

Morphine Contraindications

• Contraindicated in patients with myxoedema or hypothyroidism due to decreased basal metabolic rate
• Contraindicated in patients with epilepsy as it can worsen the condition
• Contraindicated in extreme ages (children and elderly)
• Contraindicated in patients with enlarged prostate due to increased risk of urine retention and antidiuretic hormone (ADH)

Codeine (Natural)

• Weaker than morphine as an analgesic, in causing constipation, and in addiction
• Therapeutic uses include as an anti-tussive in dry cough and dangerous cough (post-operative)
• Contraindicated in children and adolescents due to the risk of respiratory depression and epilepsy

Heroin (Semisynthetic)

• Converted to morphine in the CNS
• 100 times more potent as an anti-tussive and analgesic than morphine
• Has rapid onset and short duration, increasing the risk of abuse
• Not used clinically in most countries due to its high potency and abuse potential

Meperidine (Pethidine) (Synthetic)

• Has morphine-like and atropine-like effects
• Has advantages over morphine, including spasmolytic action, less analgesia, less respiratory depression, less addiction, and less emesis
• Does not cause pinpoint pupils, constipation, or affect the cough center, making it unsuitable as an antitussive
• May cause mydriasis (dilated pupils)
• Antagonized by naloxone, which can cause toxicity