Background The new direct acting antiviral (DAA) agents mean a breakthrough in the treatment of hepatitis C virus. However, these DAA agents are not free of drug-drug interactions (DDI), which can significantly reduce their effectiveness or produce adverse events.

Purpose The aim of this study was to describe the type and severity of DDI between DAA and concurrent patient medication, and resolve them through pharmacist interventions.

Material and methods An observational, descriptive, prospective study was carried out in the outpatients pharmacy consults of a university hospital. Every patient starting treatment from April to September 2015 was included.

The patients’ concurrent medications were screened by the pharmacist during the interviews carried out on a monthly basis, as part of an intensive pharmaceutical care programme. Potential interactions between DAA and concurrent medications were checked through the Lexi-comp application and the website http://www.hep-druginteractions.org of the University of Liverpool. Those interactions were classified according to severity, defined by FDA (B, C, D, X).

Recommendations were made by pharmacists to avoid clinically significant DDI.

Results 694 patients were included (63.4% men); mean age 56.7 (SD 12.9) years. 54.5% of patients were treated with ombitasvir/paritaprevir/ritonavir±dasabuvir, 40.6% with sofosbuvir/ledipasvir and 4.9% with others. The mean number of concurrent medication per patient was 4.7(SD 3.3).

471 DDI were recorded: 52.3% with ombitasvir/paritaprevir/ritonavir±dasabuvir, 46.1% with sofosbuvir/ledipasvir and 1.6% with others. At least one DDI was identified in 310 patients (44.7%). According to FDA severity, DDI were classified as follows: type B (2.3%), type C (43.1%), type D (47.6%) and type X (7%).

The most frequent DDI were as follows: cardiovascular agents (35.9%), proton pump inhibitors (11.9%) and antidepressants (7.4%). In most cases the drug interacting with ombitasvir/paritaprevir/ritonavir±dasabuvir was amlodipino, and with sofosbuvir/ledipasvir was omeprazole.

In 141 (29.9%) interactions, pharmaceutical intervention was required: 69 (48.9%) interventions were necessary to correct the technique of administration, 31 (22%) interventions to improve safety or effectiveness monitoring and 25 (17.7%) to withhold any of the treatments for contraindication.

Conclusion Patients treated with DDA are polymedicated and almost half of them suffered at least one moderate/severe drug interaction. The most relevant DDI were cardiovascular agents, proton pump inhibitors and antidepressants. The intensive pharmaceutical care programme has proved to be important to detect DDI and improve safety and effectiveness of clinically significant DDI.

References and/or Acknowledgements

1. Lexi-Comp. Available from: http://online.lexi.com/lco/action/interact

2. Drug interactions charts. Available from: http://www.hep-druginteractions.org/interactions.aspx

References and/or AcknowledgementsNo conflict of interest.