Morphine

Morphine (Actimorph, Sevredol)

Mechanism of action

• Opioid analgesic (strong)
• Analgesic properties are based mostly on its selective agonism to the μ-opioid receptor (MOR) which is crucial for transmission of information about pain throughout the central nervous system. These receptors are located mostly in brainstem and thalamus.
• Agonism to δ-opioid receptor (DOR) in nucleus accumbens mediates activation of the “reward pathway”.

Indications and dose

Pharmacokinetics

Onset of action:

• Oral: 20–40 minutes
• IV: 1–2 minutes

Duration of action:

• Oral: 3–6 hours 
• IV: 3–4 hours

Half-life of elimination: 2–3 hours

Metabolism: Hepatic, partly renal glucuronidation 

Elimination: Kidneys (90 %), liver (10 %)

Directions for administration

Lowest effective dose for shortest time possible is recommended.

Intravenous injections should be given over 2-3 minutes.

The oral drops should be diluted in water before administration.

he dose should be divided by 3 when patients are transferred from an oral morphine form to an intravenous form, and halved when transferred to a subcutaneous form.

Transfer from: 

1. oral dose → intravenous form: divide dose by 3
2. oral dose → subcutaneous form: divide dose by 2
   

Side-effects

Acute:

Drowsiness

Respiratory depression

Nausea, vomiting

Dysphoria

Delirium

Seizures

Bradycardia

Hypotension

Urinary retention

Constipation

Urticaria

Pruritus

Chronic:

Tolerance, addiction

Withdrawal effects

Hyperalgesia

Hypogonadism

Immunosuppression

Reversal

Rapid reversal may be achieved with Naloxone.

See more about it in Naloxone list.

Medicinal forms

Pills:

• Orodispersible – 1 mg, 2.5 mg, 5 mg, 10 mg, 20 mg, 30 mg
• Sustained-release – 10 mg, 30 mg, 60 mg, 100 mg

Solution for injection/infusion (1 mg/ml, 2 mg/ml, 10 mg/ml, 15 mg/ml, 20 mg/ml, 30 mg/ml)

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References

1. Pharm 101: Morphine • LITFL • Top 200 Drugs
2. Morphine: Uses, Interactions, Mechanism of Action | DrugBank Online
3. https://www.medicines.org.uk/emc/search?q=morphine
4. Patient-Controlled Analgesia (PCA) in Acute Pain: Pharmacological and Clinical Aspects | IntechOpen
5. Comparison between intravenous morphine versus fentanyl in acute pain relief in drug abusers with acute limb traumatic injury - PMC (nih.gov)