Lamotrigine, known commonly as Lamictal, treats seizures from epilepsy and helps manage mood in adults with bipolar I disorder. It interacts with many other drugs due to its metabolism. These interactions can lead to dangerously high lamotrigine levels and severe side effects, or conversely, levels that are too low to be effective.
Medications that dangerously increase lamotrigine levels
A significant interaction exists between lamotrigine and valproate products, requiring careful dosage and monitoring. Combining valproic acid (and divalproex) with lamotrigine can more than double lamotrigine blood concentrations. This increases the risk of severe side effects like dizziness and poor coordination, and serious skin rashes including Stevens-Johnson Syndrome. A lower starting dose and slower titration of lamotrigine are needed when taken with valproate, and any rash must be reported immediately.
Medications that decrease lamotrigine effectiveness
Other medications can increase lamotrigine clearance, reducing blood concentration and potentially leading to loss of therapeutic benefits, like breakthrough seizures or returning bipolar symptoms.
Enzyme-Inducing Antiepileptics (AEDs)
Some older AEDs, such as carbamazepine, phenytoin, phenobarbital, and primidone, accelerate the metabolism of lamotrigine, decreasing levels by up to 40-50%. This interaction can lead to a loss of seizure control or worsening bipolar symptoms. A higher maintenance dose of lamotrigine may be needed when these drugs are co-prescribed.
Hormonal Contraceptives
Estrogen-containing birth control can decrease lamotrigine levels by about 50-60%, potentially reducing efficacy. Lamotrigine levels can also fluctuate during the 'pill-free' week, increasing side effect risk. Lamotrigine dosage may need adjustment, and non-hormonal birth control is often a safer choice.
The Antibiotic Rifampin
Rifampin significantly speeds up lamotrigine metabolism, leading to lower levels and reduced effectiveness. A higher lamotrigine dose is often necessary while taking rifampin.
Certain HIV Medications
Some HIV protease inhibitors can lower lamotrigine blood levels. A higher lamotrigine dose may be needed.
Other noteworthy drug interactions
Other medications can cause different complications when combined with lamotrigine.
- Dofetilide (Tikosyn): Co-administration is strongly discouraged due to a severe interaction.
- Alcohol and CNS Depressants: Lamotrigine can enhance sedative effects, increasing drowsiness and impairing coordination.
- Acetaminophen (Tylenol): High-dose, long-term acetaminophen use may decrease lamotrigine levels.
- Cannabis/CBD: May interact and potentially increase side effect risks.
A summary of key drug interactions with lamotrigine
This table summarizes critical drug interactions with lamotrigine.
| Interacting Drug or Class | Type of Interaction | Impact on Lamotrigine | Risk and Management |
|---|---|---|---|
| Valproic Acid / Divalproex | Metabolic Inhibition | Increases levels (up to 2x) | Requires much lower starting dose and slow titration. |
| Carbamazepine, Phenytoin, Phenobarbital | Metabolic Induction | Decreases levels (40-50%) | Reduces efficacy, risking breakthrough seizures or mood episodes. Requires higher maintenance dose of lamotrigine. |
| Hormonal Contraceptives (Estrogen) | Metabolic Induction | Decreases levels (50-60%) | Reduces efficacy, risking breakthrough seizures or unplanned pregnancy. Dosage adjustment needed when starting/stopping. |
| Rifampin (antibiotic) | Metabolic Induction | Decreases levels significantly | Reduces efficacy. Requires higher dose of lamotrigine during rifampin treatment. |
| Dofetilide (heart drug) | Pharmacodynamic | Potential for severe adverse effects | Avoid concurrent use due to serious interaction risks. |
Managing potential drug interactions
Transparent communication with healthcare providers and pharmacists is crucial. Provide a complete list of all medications and supplements. Your healthcare team can assess risks and determine if dose adjustments, monitoring, or an alternative treatment is needed. For those using hormonal contraceptives, discussing non-estrogen options may be advisable. When stopping an interacting medication, the lamotrigine dose may need adjustment.
Conclusion
Knowing what medication should you not take with lamotrigine is vital. Various medications can alter lamotrigine's therapeutic window. Interactions can lead to reduced effectiveness or life-threatening conditions. Working closely with a healthcare provider is the safest approach.
