Observational study of drug-drug interactions in oncological inpatients.

OBJECTIVE To determine the prevalence of potential clinically relevant drug- drug interactions in adult oncological inpatients, as well as to describe the most  frequent interactions. A standard database was used. METHOD An observational, transversal, and descriptive study including patients  admitted to the Oncology Service of a reference hospital. All prescriptions were  collected twice a week during a month. They were analysed using Lexicomp®  database, recording all interactions classified with a level of risk: C, D or X. RESULTS A total of 1 850 drug-drug interactions were detected in 218  treatments. The prevalence of treatments with at least one clinically relevant  interaction was 95%, being 94.5% for those at level C and 26.1% for levels D  and X. The drugs most commonly involved in the interactions detected were  opioid analgesics, antipsychotics (butyrophenones), benzodiazepines,  pyrazolones, glucocorticoids and heparins, whereas interactions with  antineoplastics were minimal, highlighting those related to paclitaxel and  between metamizole and various antineoplastics. CONCLUSIONS The prevalence of clinically relevant drug-drug interactions rate  was very high, highlighting the high risk percentage of them related to level of  risk X. Due to the frequency of onset and potential severity, highlighted the  concomitant use of central nervous system depressants drugs with risk of  respiratory depression, the risk of onset of anticholinergic symptoms when  combining morphine or haloperidol with butylscopolamine, ipratropium bromide  or dexchlorpheniramine and the multiple interactions involving metamizole.