The Influence of CYP2C19 Polymorphisms on the Safety and Efficacy of Voriconazole

Voriconazole is a drug used to treat invasive fungal infections. The amount of voriconazole in a person's blood helps to determine how effectively it treats an infection, and how safe it is. Patients respond differently when receiving the same dose - some clearly benefit, other patients experience side effects, and others see limited improvement in their infection. Voriconazole is broken down in the liver mainly by an enzyme called CYP2C19, before being excreted from the body. The activity of CYP2C19 differs between people because of variation in the DNA that encodes the body's instructions to make CYP2C19. If CYP2C19 activity is very high, voriconazole blood levels may remain below the target range when a patient receives a standard dose of voriconazole, which may be insufficient to treat their infection. By contrast, decreased CYP2C19 activity due to genetic variation may result in excessively high voriconazole blood levels, predisposing to serious side effects. Therefore, knowing a patient's CYP2C19 genetic makeup is very important for predicting their response to voriconazole. Thus, the investigators aim to determine the influence of genetic variation in CYP2C19 on the frequency and severity of side effects related to voriconazole, and on the effectiveness of voriconazole for treating serious fungal infections. The findings from this study will contribute to determining the optimal dose of voriconazole that patients with different genetic variants in CYP2C19 should be started on, and will take us one step closer to both understanding the genetic structure of CYP2C19 in the Turkish population, and to 'personalised medicine'.