Table 3.

Interactions of opioids with other drugs.

Stimulants CNS	Increase of ventricular arrhythmias (methadone+atomoxetine)
Antiepileptic drugs	Dextropropoxyphene increases the effect of carbamazepine
Tricyclic antidepressants	Increase of sedative effects of opioids
	Increase of toxic effects (convulsions, e.g., tramadol)
	Inhibition of morphine glucuronidation
Monoamine oxidase inhibitors (MAOIs)	Excitation and depression of CNS (pethidine, tramadol)
Selective serotonin reuptake inhibitors (SSRIs)	Toxic CNS effects (convulsions, tramadol)
Anticoagulants	Increase of anticoagulant effects (dextropropoxyphene, tramadol)
Antiarrhythmics	Merphine can increase the concentration of esmolol in plasma
Drugs affecting gastrointestinal tract	Metoclopramide and domperidone antagonize the gastrointestinal effects of opioid analgesics
	Cimetidine inhibits the metabolism of opioids
	Ranitidine decreases the concentration of morphine and conversion to active metabolites
Antibacterial drugs	Opioids decrease the concentration of ciprofloxacin
	Erythromycin increases opioid concentration
	Rifampicin decreases opioid concentration
Antiviral drugs	Metadone can increase the concentration of zidovudine
	Ritonavir can increase the concentration of opioid analgesics (fentanyl, petidine, dextropropoxyphene)
Antifungal drugs	Vorikonazol increases concentration of methadone and alfentanyl
	Ketoconazole increases the concentration of opioid analgesics