-Blockers and cholinomimetics cause bradycardia, AV blocks and hypotension via their synergistic negative chronotropic effect.
-Blockers and non-dihydropyridine calcium channel blockers (diltiazem, verapamil)
cause bradycardia, asystole, sinus arrest due to their additive effect on the heart.
-Blockers and digoxin cause bradycardia and AV block via their additive effect.
-Blockers and dronedarone cause bradycardia as both drugs slow heart rate and
dronedarone can inhibit CYP2D6 metabolism of some -blockers.
-Blockers and antipsychotic phenothiazines cause hypotension as they have an additive effect.
-Blockers and propafenone cause profound hypotension and cardiac arrest as they have a similar effect on the heart, propafenone can inhibit metabolism of some -blockers through inhibition of CYP2D6.
Some -blockers and some SSRIs (citalopram, escitalopram) cause bradycardia, AV blocks and hypotension can occur with fluoxetine and paroxetine which are potent inhibitors of CYP2D6 and thus slow metabolism of some -blockers.
Increased blood levels/toxicity: Inhibitors of CYP2D6 including amiodarone, cimetidine (but not ranitidine), delavudin, fluoxetine, paroxetine, quinidine and ritonavir; and inhibitors of CYP1A2 including imipramine, cimetidine, ciprofloxacin, fluvoxamine, isoniazid, ritonavir, theophylline, zileuton, zolmitriptan and rizatriptan.
Decreased blood levels/decreased efficacy: Inducers of hepatic drug metabolism
including rifampin, ethanol, phenytoin and phenobarbital.
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