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Histamine release by morphine and diamorphine in man
D E Withington1, J A Patrick, F Reynolds
1United Medical and Dental School, Guys Hospital, London.
Abstract:
Intravenous morphine and diamorphine are routinely used for postoperative analgesia but the relative histamine releasing abilities of these drugs have not been compared in man. Thirty-eight patients were randomly allocated to receive morphine (0.16 mg.kg-1) or diamorphine (0.08 mg.kg-1) after abdominal surgery. Blood samples for histamine were taken before, and at timed intervals after, opioid administration and analysed by an isotopic radioenzymatic technique. Haemodynamic parameters and pain scores were recorded before and after analgesic administration, and a series of eight basophil histamine release studies was also performed. Significant histamine release (plasma concentration > 2 ng.ml-1 or rise of > 700% baseline) occurred in 23.5% of the morphine group and 21.1% of the diamorphine group. Histamine was released earlier in those receiving diamorphine, but no significant change in haemodynamic parameters occurred, and no histamine release was demonstrated in the basophil histamine release studies. These findings suggest that morphine and diamorphine release histamine from mast cells rather than basophils.
Insights
Morphine and diamorphine, used for postoperative pain relief, both trigger histamine release. This study suggests these opioids release histamine from mast cells, not basophils, with no significant hemodynamic effects observed.
Area of Science:
- Pharmacology
- Anesthesiology
- Immunology
Background:
- Intravenous morphine and diamorphine are common postoperative analgesics.
- Their comparative histamine-releasing potential in humans remains unquantified.
Purpose of the Study:
- To compare the histamine-releasing effects of intravenous morphine and diamorphine in patients undergoing abdominal surgery.
Main Methods:
- Thirty-eight patients received either morphine (0.16 mg.kg-1) or diamorphine (0.08 mg.kg-1).
- Plasma histamine levels were measured using an isotopic radioenzymatic technique at timed intervals post-administration.
- Hemodynamic parameters, pain scores, and basophil histamine release were also assessed.
Main Results:
- Significant histamine release occurred in 23.5% of the morphine group and 21.1% of the diamorphine group.
- Histamine release was observed earlier with diamorphine administration.
- No significant changes in hemodynamic parameters or histamine release from basophils were detected.
Conclusions:
- Both morphine and diamorphine induce histamine release in a subset of patients.
- Findings indicate that histamine release originates from mast cells rather than basophils.
- Clinical implications for postoperative pain management with these opioids warrant further investigation.