Drug Interactions between galantamine and Marax

Both smoking and excessive caffeine consumption can alter the blood levels of theophylline, which may affect the dosing. Tobacco and marijuana smoke (including secondhand exposure) generally reduces, while caffeine increases, blood levels. In addition, caffeine is a stimulant and may add to the side effects of theophylline such as headache, insomnia, and increases in blood pressure and heart rate. It is best to avoid smoking and to limit caffeine consumption during theophylline therapy. Talk to a healthcare professional if you have any questions or concerns. If you start smoking or undergo smoking cessation, your doctor may need to monitor your blood levels more closely to determine if you need a dose adjustment of theophylline. You should stop taking theophylline and seek medical attention if you experience potential signs and symptoms of excessive drug levels such as nausea, vomiting, persistent headache, insomnia, and rapid heartbeat. 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.

When theophylline is given with enteral (tube) feedings, blood levels may be decreased due to interference with its absorption. This may reduce the effectiveness of the medication. To minimize potential for interaction, you may interrupt the feeding for one hour before and one hour after the theophylline dose. You may need more frequent blood tests to monitor theophylline levels.

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Alcohol can increase the nervous system side effects of hydrOXYzine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with hydrOXYzine. Do not use more than the recommended dose of hydrOXYzine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

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Consumer information for this interaction is not currently available.

ADJUST DOSING INTERVAL: The administration of galantamine with food and adequate fluid intake may reduce the impact of nausea, vomiting, diarrhea, anorexia, and weight loss that are commonly associated with acetylcholinesterase inhibitors (AChEIs). According to product labeling, the administration of food with various galantamine formulations (e.g., liquid, immediate-release tablets, modified/extended-release capsules) has no significant effect on the systemic absorption (AUC) of galantamine. While the presence of food has been shown to delay the rate of absorption (Tmax) and reduce peak concentration (Cmax), these changes are unlikely to be clinically significant. For example, when galantamine modified release was given after food, Tmax increased by approximately 30 minutes. Similarly, in 24 healthy elderly subjects, the presence of food with galantamine immediate release tablets (12 mg twice a day) delayed the Tmax by 1.5 hours and decreased the Cmax by about 25% without affecting the AUC.

MONITOR: Grapefruit and grapefruit juice may increase the plasma concentrations of galantamine, which is partially metabolized by the CYP450 3A4 isoenzyme. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but has been reported with both moderate and potent CYP450 3A4 inhibitors. When study subjects (n=16) received the potent CYP450 3A4 inhibitor ketoconazole (200 mg twice daily for 4 days) with galantamine (4 mg twice daily for 8 days), the systemic exposure (AUC) of galantamine increased by 30%. However, when study subjects (n=16) received the moderate CYP450 3A4 inhibitor erythromycin (500 mg 4 times daily for 4 days) with galantamine (4 mg twice daily for 6 days), the AUC of galantamine only increased by 10%. In general, the effects of grapefruit products are concentration-, dose-, and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. While the clinical significance of this interaction is unknown, increased exposure to galantamine may lead to AChEI related adverse effects such as vagotonic effects on the heart rate (e.g., bradycardia and heart block), neurologic side effects (e.g., seizure activity), respiratory distress, bladder outflow obstruction, dizziness or syncope, nausea, vomiting and/or diarrhea.

MANAGEMENT: According to product labeling, galantamine should be administered with food and adequate fluid intake to reduce the impact of cholinergic-related gastrointestinal adverse effects (e.g., nausea, vomiting, diarrhea, anorexia, and weight loss). Caution and closer monitoring for AChEI related adverse effects may advisable if galantamine is used in combination with grapefruit and/or grapefruit juice. Modified and/or extended-release formulations must also be swallowed whole and not crushed, chewed, or divided.

Ask your doctor before using theophylline together with caffeine. Using these medications together may increase some of the side effects of theophylline. This can cause nausea, vomiting, insomnia, tremors, restlessness, uneven heartbeats, and seizure (convulsions). Avoid drinks or foods that contain caffeine, such as coffee, tea, cola, and chocolate. You may need a dose adjustment or special test if you use both medications. 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.

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Both ePHEDrine and caffeine can increase blood pressure and heart rate, and combining them may enhance these effects. Talk to your doctor before using these medications, especially if you have a history of high blood pressure or heart disease. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. 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.

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