Major
Morphine × Pregabalin
Natural opium alkaloids×Gabapentinoids (antiepileptics)
Mechanism
Pregabalin acts via the α2δ subunit of calcium channels and depresses the central nervous system. Morphine suppresses the respiratory centre via μ-opioid receptors. Effects are additive.
Symptoms
Drowsiness, slowed breathing (rate below 12/min), cyanosis of lips. Severe cases include respiratory arrest. Older patients: fall risk.
Management
The combination is possible in neuropathic pain or palliative cancer pain with careful titration. Keep doses minimal, provide naloxone to the patient and family, monitor respiratory rate and saturation.