The recognition of interacting drugs is critical for any healthcare providers, including pharmacists, to decrease the DDIs and, consequently, reduce the drug-related morbidity and mortality that may occur as a result of these interactions [5, 28]. Although thousands of articles on drug interactions have been published and numerous computerized screening systems have been developed, patients continue to suffer from adverse drug interactions. It was found that about twenty percent of the adverse drug effects in the developed countries, which are responsible for more than 700,000 deaths, are due to drug–drug interactions [14]. Possible methods for reducing the risk of drug interactions include improving healthcare providers' knowledge, improving computerized screening systems, providing information on patient risk factors, increasing pharmacogenetic information, more attention to drug administration risk factors, and improving patient education on drug interactions.

In this survey, we assessed the ability of pharmacists to recognize clinically significant drug combinations. It was found that among DDI information sources, internet or mobile applications and medical textbooks were the most used sources of information. The majority of the participants (47.1%) tended to receive information regarding DDIs from electronic sources, which is consistent with a previous study conducted in Iran [29]. The possible explanation for this finding may be the high percentages of young participants in the present study, and people in this age group are usually interested in technology and use it in many fields. A small percentage of the participants in our survey (1.2%) reported that they use package inserts, which is a risk factor for incorrect use of drugs [30].

Our study showed no significant differences in the proportion of community pharmacists and hospital pharmacists who correctly answered the same number of questions about DDIs. The level of the participants' knowledge of DDIs was 58.25% (average of correct answers about DDIs), and this finding is comparable to another study (53.3%) [31]. However, our results are not consistent with another study [24] that revealed a level of knowledge among pharmacists of about 37.3%, but the later study included 26 drug pairs; however, our study included 19 pairs, and these differences in drug pairs may be the cause of the differences in the level of the participant's knowledge on DDIs.

Among the drug pairs selected to assess DDIs knowledge, sildenafil, and isosorbide mononitrate were the most highly recognized drug pairs (78.8%), which is consistent with another study [32]. The lowest recognized pairs were alprazolam and itraconazole (17.8%), which are contraindicated with each other. In accordance with another study [5], even if one justified that the drug combinations classified as contraindicated could be used with close monitoring and considered both choices to be correct, up to 65% of the participants remained unsure if there was a potential interaction or not. In our study, we tried to investigate the predictors of DDI knowledge of participants, including age, education, setting, years of practice, and the participants’ attitudes toward DDIs. It was found that a significant correlation exists between participants’ age and their knowledge level in DDIs. The older participants answered more DDI questions than younger ones, which is consistent with another study that used identical drug pairs as our study [33]. Another study, in contrast to ours, found no connection between age and DDI knowledge level [34], but this may be explained as the later study involved participants of relatively the same age.

Another predictor of DDI knowledge is the education level, which was found to have a significant correlation with the level of knowledge of DDIs. Unexpectedly, participants with bachelor’s and postgraduate certificate holders recognized a higher number of interactions than did those with Ph.D. and board-certified pharmacists, and this finding was in accordance with a study carried out in Khartoum state and showed that pharmacists with bachelor's recognized higher number of DDIs than those with master [31]. The results of our study were in contrary to a previous study [33] that reported that participants' education level did not affect the knowledge level of DDIs. These findings could be due to several factors, including the fact that Ph.D. holders are not recent graduates and may not have as good recall of DDIs, as well as the fact that the majority of pharmacists have bachelor's or postgraduate diploma degrees rather than PhDs and board certifications.

Interestingly, the number of years of experience of the participants was not a significant predictor of DDI knowledge level, and this is consistent with other studies that used different drug pairs for DDI knowledge assessment [5, 31].

Regarding attitudes toward DDIs and their relation to the level of DDI knowledge, it was found that participants who always consider DDIs while prescribing and checking about DDIs when not sure about them recognized a more significant number of DDIs than those who did not, and these results are consistent with previous study conducted in China [33]. This indicates the strong association between the participants' tendency to check references and their knowledge of PDDIs, as proved by the correct recognition of the drug pair interactions.

Astonishingly, this study revealed no significant association between setting (whether community or hospital pharmacists) and the level of their knowledge of DDIs.

The findings of the present study have several implications for practice. This article highlights an important issue that requires urgent attention in Egypt which is the improvement of drug–drug interaction knowledge among community and hospital pharmacists. It is crucial for improving patient safety and healthcare outcomes in the country to ensure the rational and optimal use of drugs. By raising awareness of this issue and identifying potential solutions, this study makes an important contribution to the field of healthcare in Egypt and beyond. Our study has identified some recommendations to improve the knowledge and practice of hospital and community pharmacists regarding DDIs. Based on the study’s findings, it is recommended that continuing education and training programs should be developed for hospital and community pharmacists in Egypt to improve their knowledge of DDIs. The Egyptian Ministry of Health should develop guidelines and protocols for the management of DDIs in hospitals and community pharmacies to ensure consistency in practice. Additionally, these pharmacies should have access to electronic databases that provide up-to-date information on DDIs to support their practice. This study highlights the need for ongoing education and training programs, updated guidelines, and increased resources to support pharmacists in their efforts to provide safe and effective care to patients. Finally, future studies should be conducted to assess the impact of education and training programs on hospital and pharmacists’ knowledge and practice regarding DDIs.

The limitation of our study is that the 19-drug pairs might not be adequate to reflect the extent of knowledge applicable to the vast number of PDDIs. In addition, the study’s sample size may limit the generalizability of the findings. The sample size is small or not representative of the entire population of hospital and community pharmacists in Egypt, so, the results may not accurately reflect the overall knowledge level of pharmacists in the country. Additionally, the study’s reliance on self-reported data from pharmacists introduces the possibility of response bias. Participants may overestimate their knowledge to present themselves in a more favorable light or may underreport their knowledge about DDIs due to various reasons, such as social desirability bias. Furthermore, the study focuses solely on assessing the pharmacists’ knowledge without considering other factors that may influence their ability to apply that knowledge in practice, such as time constraints, workload, or access to resources.

In addition, future studies of larger sample sizes of pharmacists and more drug pairs are required to face the challenges and limitations of this study taking into consideration other factors such as time constraints, workload, or access to resources that may affect their ability to apply that knowledge in practice,