A probable drug-to-drug interaction between voriconazole and haloperidol in a slow metabolizer of CYP2C19

We present a case of Aspergillus fumigatus renal abscess treated with voriconazole of a HIV-positive 43-year-old male patient. Following haloperidol treatment we observed an unexpected increase in voriconazole through concentrations and liver function tests. CYP2C19*2 loss of function allele was stated, an interaction probably explained by the introduction of haloperidol, a weak CYP3A4 inhibitor. Therapeutic drug monitoring and CYP2C19 genotyping may be suggested when administering voriconazole to complex patients.