Drug Interactions between benzgalantamine and fluoxetine / olanzapine

Using OLANZapine together with FLUoxetine can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have any questions or concerns. Your doctor may already be aware of the risks, but has determined that this is the best course of treatment for you and has taken appropriate precautions and is monitoring you closely for any potential complications. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with these medications, whether together or alone. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with potent inhibitors of CYP450 2D6 and/or 3A4 may increase the plasma concentrations of galantamine, which is also an active metabolite of benzgalantamine. Up to 75% of galantamine is eliminated via metabolism and in vitro studies have identified CYP450 2D6 and 3A4 as the major isoenzymes involved. The systemic exposure (AUC) of galantamine (4 mg, 8 mg, or 12 mg twice daily) increased by 40%, 45%, and 48%, respectively, when administered to healthy volunteers (n=16) also receiving the strong CYP450 2D6 inhibitor paroxetine. Similarly, the strong CYP450 3A4 inhibitor ketoconazole (200 mg twice daily) increased the AUC of galantamine (4 mg twice daily) by 30% when given concurrently to study subjects (n=16). An increase in the AUC of galantamine can increase the risk of acetylcholinesterase inhibitor-related adverse effects. One potential side effect of galantamine is bradycardia, which may increase the risk of QT prolongation. If the inhibitor being coadministered is also associated with QT prolongation (e.g., adagrasib, ceritinib, fluoxetine, ketoconazole, levoketoconazole, mifepristone), the risk of experiencing this adverse effect may be further increased.

MANAGEMENT: Caution and closer monitoring of the pharmacologic response to galantamine and its prodrug benzgalantamine is advised whenever a potent CYP450 2D6 and/or 3A4 inhibitor is added to or withdrawn from therapy. Some authorities suggest considering a reduction in the galantamine dose for patients on concurrent potent CYP450 2D6 and/or 3A4 inhibitors. Patients should be monitored more closely for acetylcholinesterase inhibitor related adverse effects including vagotonic effects on the heart rate (e.g., bradycardia, which may increase the risk of QT prolongation, and heart block), neurologic side effects (e.g., seizure activity), respiratory distress, bladder outflow obstruction, dizziness or syncope, nausea, vomiting and diarrhea. These effects may be more severe when the coadministered inhibitor shares a similar adverse effect profile with galantamine.

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Due to opposing effects, agents that possess anticholinergic activity (e.g., sedating antihistamines; antispasmodics; neuroleptics; phenothiazines; skeletal muscle relaxants; tricyclic antidepressants; class IA antiarrhythmics especially disopyramide; carbamazepine; cimetidine; ranitidine) may negate the already small pharmacologic benefits of acetylcholinesterase inhibitors in the treatment of dementia. These agents may also adversely affect elderly patients in general. Clinically significant mental status changes associated with anticholinergic agents can range from mild cognitive impairment to delirium, and patients with Alzheimer's disease and other dementia are especially sensitive.

MANAGEMENT: Drugs that possess anticholinergic activity should generally be avoided in patients with Alzheimer's disease or other cognitive impairment, regardless of whether they are receiving an acetylcholinesterase inhibitor. For patients requiring treatment to counteract adverse effects of acetylcholinesterase inhibitor therapy (e.g., gastrointestinal intolerance, urinary problems), an agent without anticholinergic properties should be used whenever possible. Otherwise, a dosage reduction, slower titration, or even discontinuation of the acetylcholinesterase inhibitor should be considered. For patients who are already receiving an acetylcholinesterase inhibitor with anticholinergic agents, every attempt should be made to discontinue the latter or substitute them with less anticholinergic alternatives. Caution is required, however, since anticholinergic withdrawal may occur. Seizures have been reported following abrupt discontinuation of anticholinergics during acetylcholinesterase inhibitor therapy.