Carbamazepine × Linezolid

Linezolid is a reversible, non-selective monoamine oxidase inhibitor (MAOI) (linezolid SmPC), and the Spanish carbamazepine SmPC contraindicates carbamazepine with MAOIs; the US label does not recommend the combination and calls the grounds theoretical (US carbamazepine label). Both drugs suppress the bone marrow: linezolid causes anaemia, leukopenia, thrombocytopenia and pancytopenia, with risk rising with treatment length (linezolid SmPC), and carbamazepine lowers white cell and platelet counts and is rarely linked to agranulocytosis and aplastic anaemia (carbamazepine SmPC). As a strong inducer of liver enzymes, carbamazepine may lower linezolid exposure; the clinical significance is unknown (US linezolid label).

Weakness, pallor and breathlessness on exertion (anaemia), frequent infections and fever (leukopenia), bruising and bleeding (thrombocytopenia). Linezolid-related bone marrow suppression is more likely with courses longer than 10–14 days and in older patients (linezolid SmPC).

The combination is contraindicated by the Spanish carbamazepine SmPC, which contraindicates carbamazepine with monoamine oxidase inhibitors (MAOIs) and requires MAOIs to be stopped at least 2 weeks before carbamazepine is started (carbamazepine SmPC). The linezolid SmPC describes linezolid as a reversible, non-selective MAOI (linezolid SmPC), while the linezolid labels do not mention carbamazepine. The FDA wording is softer: carbamazepine with MAOIs is not recommended on theoretical grounds (US carbamazepine label). If linezolid is still given to a patient on carbamazepine, check a full blood count with platelets weekly: the linezolid SmPC requires this for all patients and asks for especially close monitoring when other drugs that lower haemoglobin or platelets are taken (linezolid SmPC). If significant bone marrow suppression develops, stop linezolid unless continuing it is absolutely necessary (linezolid SmPC).