Drug Interaction Report

MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

Switch to consumer interaction data

MONITOR: In vitro studies have shown that lamotrigine exhibits class IB antiarrhythmic activity at therapeutically relevant concentrations. Lamotrigine has shown in vitro effects on the human cardiac sodium channels similar to that of other Class 1B antiarrhythmic drugs. In healthy individuals, a thorough QT study did not show slowed ventricular conduction (widen QRS) with lamotrigine; however, the risk of slow ventricular conduction and proarrhythmias, including sudden death may be increased in patients with structural heart disease or myocardial ischemia. Based on this data, there is a concern that concomitant use of other sodium channel blockers may increase the risk of proarrhythmias.

MANAGEMENT: Caution and clinical monitoring are recommended if concomitant use of other sodium channel blockers is needed. Due to the potential for increased risk of proarrhythmias, the manufacturer recommends lamotrigine be avoided in patients who have cardiac conduction disorders (e.g., second- or third-degree heart block), ventricular arrhythmias, or cardiac disease or abnormality (e.g., myocardial ischemia, heart failure, structural heart disease, Brugada syndrome or other sodium channelopathies). A joint task force of the International League Against Epilepsy and the American Epilepsy Society issued an advisory on Feb 25, 2021, for healthcare professionals in response to the FDA safety warning on the cardiac effects of lamotrigine. For patients under 60 years with no cardiac risk factors, they advise that clinicians should prescribe lamotrigine as usual. For patients with cardiac risk (over 60 years and under 60 years with known cardiac disease or significant risk factors), they advise clinicians to consider obtaining an ECG prior to initiating lamotrigine and repeating ECG as the serum lamotrigine level approaches the upper limit of the therapeutic range and/or with concomitant use of other sodium channel blockers or substances known to impair atrioventricular and/or intra-ventricular cardiac conduction. They also advise clinicians to consider obtaining an ECG and/or cardiology consult in patients with sudden onset syncope or pre-syncope with loss of muscular tone without a clear vasovagal or orthostatic cause. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate an irregular heart rhythm such as dizziness, lightheadedness, fainting, palpitation, shortness of breath, or syncope.

Switch to consumer interaction data

MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

Switch to consumer interaction data

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

Switch to consumer interaction data

MONITOR: Oral caffeine may significantly increase the bioavailability of melatonin. The proposed mechanism is inhibition of CYP450 1A2 first-pass metabolism. After administration of melatonin 6 mg and caffeine 200 mg orally (approximately equivalent to 1 large cup of coffee) to 12 healthy subjects, the mean peak plasma concentration (Cmax) of melatonin increased by 137% and the area under the concentration-time curve (AUC) increased by 120%. The metabolic inhibition was greater in nonsmokers (n=6) than in smokers (n=6). The greatest effect was seen in subjects with the *1F/*1F genotype (n=7), whose melatonin Cmax increased by 202%. The half-life did not change significantly. The clinical significance of this interaction is unknown.

According to some authorities, alcohol may reduce the effect of melatonin on sleep. The mechanism of this interaction is not fully understood.

In addition, CYP450 1A2 inducers like cigarette smoking may reduce exogenous melatonin plasma levels. In a small clinical trial (n=8), habitual smokers had their melatonin plasma levels measured two times, each after a single oral dose of 25 mg of melatonin. They had smoked prior to the first measurement but had not smoked for 7 days prior to the second. Cigarette smoking significantly reduced melatonin plasma exposure (AUC) as compared to melatonin levels after 7 days of smoking abstinence (7.34 +/- 1.85 versus 21.07 +/- 7.28 nmol/L*h, respectively).

MANAGEMENT: Caution and monitoring are recommended if melatonin is used with inhibitors of CYP450 1A2 like caffeine or inducers of CYP450 1A2 like cigarette smoking. Consumption of alcohol should be avoided when taking melatonin.

Switch to consumer interaction data

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

Switch to consumer interaction data