Background: Antibiomania is a rare but recognized side effect with yet unclear definite pathogenesis although multiple hypotheses have been proposed. The novelty of this case is the suspected pharmacodynamic drug-drug interaction between clarithromycin and amoxicillin-clavulanic acid.

Case presentation: We present the occurrence of a brief manic episode concerning a 50-year-old man with no psychiatric history, first started on amoxicillin-clavulanic acid therapy and then switched to clarithromycin for left basal pneumonia. Shortly after the antibiotic prescription, he presented psychiatric symptomatology (logorrhea, elevated mood, irritability, increase in physical activity and delusions). The antibiotic was stopped and the patient received lorazepam (2.5 mg p.o.) to treat psychomotor agitation. Approximately 12 h after clarithromycin cessation, amelioration was already observed, supporting the diagnosis of a clarithromycin-induced manic episode. Amoxicillin-clavulanic acid was then reintroduced because of the pneumonia and psychiatric symptoms reemerged. This second antibiotic was also stopped, and 1 week later, the patient was symptom-free.

Conclusion: The emergence of psychiatric side effects related to antibiotherapy, which is a common treatment, can greatly impact a patient's quality of life. Early recognition and intervention could substantially influence the administered medical care and recovery. Moreover, given the widespread use of antibiotics including in combination, we thought our case report might be clinically useful as a clinical reminder relevant to the use of antibiotic combinations.