Aripiprazole Does Not Increase Lamotrigine Levels
Aripiprazole (Abilify) does not increase lamotrigine (Lamictal) levels and no dosage adjustment of lamotrigine is required when these medications are used in combination. 1, 2
Evidence on Aripiprazole-Lamotrigine Interaction
The FDA-approved drug label for aripiprazole explicitly states that "no dosage adjustment is necessary for lamotrigine when co-administered with aripiprazole" 1. This is based on pharmacokinetic studies that have demonstrated no clinically significant interaction between these medications.
Research specifically investigating this combination confirms this lack of interaction:
- A dedicated pharmacokinetic study in patients with bipolar I disorder found that aripiprazole had no meaningful effect on lamotrigine steady-state pharmacokinetics 2
- When comparing lamotrigine alone versus lamotrigine with aripiprazole:
- Maximum plasma concentration remained similar (26 ng/mL vs 23 ng/mL)
- Area under the concentration-time curve was comparable (434 ng/h/mL vs 394 ng/h/mL)
- No changes to lamotrigine dose-normalized plasma trough concentrations were observed
Clinical Implications
This pharmacokinetic profile makes the combination potentially useful in bipolar disorder treatment:
- The combination has been studied in clinical trials for bipolar I disorder maintenance treatment 3
- The combination was generally safe and well tolerated in clinical studies 2, 3
Known Medication Interactions with Lamotrigine
While aripiprazole doesn't affect lamotrigine levels, it's important to be aware of medications that do interact with lamotrigine:
| Medication | Effect on Lamotrigine Levels |
|---|---|
| Valproic acid | Increases (↑ half-life to 48-59 hours) [4] |
| Enzyme inducers (carbamazepine, phenytoin) | Decreases (↓ half-life to 13.5-15 hours) [4] |
| Oral contraceptives | Decreases [5] |
Monitoring Recommendations
When using lamotrigine with aripiprazole:
- No special monitoring of lamotrigine levels is required based on this combination alone
- Follow standard monitoring practices for each medication individually
- If other medications that do affect lamotrigine levels (like valproic acid) are added or removed, monitoring lamotrigine levels 1-2 weeks after the change may be appropriate 5
Common Pitfalls to Avoid
Confusing with other combinations: Unlike valproic acid which significantly increases lamotrigine levels (requiring dose reduction of lamotrigine), aripiprazole does not have this effect
Overlooking other drug interactions: While aripiprazole doesn't affect lamotrigine levels, be aware that lamotrigine can increase carbamazepine-10,11-epoxide levels 4
Ignoring titration requirements: Remember that lamotrigine still requires slow titration to minimize risk of serious rash, regardless of concomitant aripiprazole use
In conclusion, the combination of aripiprazole and lamotrigine can be used without dosage adjustment of either medication based on their interaction profile, making this a straightforward combination from a pharmacokinetic perspective.