Does combination with Abilify (aripiprazole) increase Tegretol (carbamazepine) levels?

Drug Interaction Between Abilify (Aripiprazole) and Tegretol (Carbamazepine)

No, Abilify (aripiprazole) does not increase Tegretol (carbamazepine) levels. In fact, the opposite occurs - carbamazepine significantly decreases aripiprazole levels through enzyme induction.

Mechanism of Interaction

The interaction between aripiprazole and carbamazepine is primarily based on their metabolic pathways:

• Carbamazepine is a potent inducer of CYP3A4 enzymes in the liver 1
• Aripiprazole is extensively metabolized by CYP3A4 enzymes 2
• When used together, carbamazepine increases the metabolism of aripiprazole, resulting in decreased aripiprazole blood levels 2, 3

Clinical Significance and Management

Effect on Aripiprazole Levels

• Carbamazepine significantly reduces aripiprazole plasma concentrations through enzyme induction 3
• This can lead to reduced clinical efficacy of aripiprazole 3
• The FDA label specifically states: "When carbamazepine is added to aripiprazole, the aripiprazole dose should be doubled. Additional dose increases should be based on clinical evaluation." 1

Effect on Carbamazepine Levels

• There is no evidence that aripiprazole increases carbamazepine levels 2
• The FDA label for aripiprazole specifically states that "no dosage adjustment is necessary for valproate, lithium, lamotrigine, lorazepam, or sertraline when co-administered with aripiprazole" but does not include carbamazepine in this list 2

Recommendations for Clinical Practice

When prescribing these medications together:

1. Double the aripiprazole dose when adding carbamazepine 2, 1
2. Monitor for decreased aripiprazole efficacy even after dose adjustment 3
3. Consider therapeutic drug monitoring of aripiprazole levels if available
4. Watch for signs of treatment failure with aripiprazole due to subtherapeutic levels

Other Important Considerations

• While this combination doesn't increase carbamazepine levels, both medications can potentially affect liver function 3
• The combination should be used with caution and liver function tests should be monitored periodically 3
• Alternative mood stabilizers with fewer drug interactions (such as lamotrigine) may be considered if appropriate for the patient's condition 4

Common Pitfalls to Avoid

• Don't assume bidirectional interaction: While many drug interactions are bidirectional, this one primarily affects aripiprazole levels, not carbamazepine levels
• Don't overlook the need for aripiprazole dose adjustment: Failure to increase the aripiprazole dose may result in treatment failure
• Don't confuse with other antipsychotic-anticonvulsant combinations: Some combinations (like fluvoxamine with aripiprazole) can increase antipsychotic levels, but this is not the case with carbamazepine 3

In summary, when combining Abilify with Tegretol, the primary concern is decreased Abilify effectiveness rather than any change in Tegretol levels.