Moderate
Established
Description
Cetirizine may add to morphine-induced CNS depression, increasing sedation and potentially enhancing respiratory depression, particularly with higher doses of either agent.
Mécanisme
Morphine produces CNS and respiratory depression via mu-opioid receptor activation; cetirizine's partial CNS H1 antagonism provides additive sedation through complementary mechanisms.
Signification clinique
The FDA black box warning for opioids includes all CNS depressants; pharmacodynamic data confirm that sedation is augmented with antihistamine co-administration.
Prise en charge
Use the lowest effective doses of both agents; monitor respiratory rate and sedation level; avoid concurrent use of other CNS depressants.