Deprescribing is the planned and supervised process of dose reduction or tapering, and stopping of medication, which might be causing harm, or is no longer of benefit to the patient, with the goal of managing polypharmacy and improving outcomes. This research aimed to explore the need for, and the barriers and facilitators of deprescribing in primary care in a healthcare system where it has not been researched, implemented, or provided. Four phases of research were carried out. The systematic review performed in the first phase of this research shows community-based pharmacists can successfully lead deprescribing interventions and are valuable partners in deprescribing. Second phase of research unveils the finding that the majority of adults 40 years and older (84%) would be willing to deprescribe one or more medications, with older adults (65 years and older) being more willing to have medications deprescribed than younger adults (χ2 (1) = 4.06; p = 0.044). Furthermore, majority of participating adults (71%) would feel comfortable with pharmacist’s involvement in deprescribing, and 69% believes pharmacists have competencies to suggest deprescribing to physicians. Positive opinion on pharmacists' involvement was assessed as a predictive factor for positive attitude towards deprescribing (aOR = 2.351, 95% CI = 1.176 – 4.699; p = 0.016). Comprehensive Healthcare providers’ OPinions, Preferences, and attitudEs towards Deprescribing (CHOPPED) questionnaire was developed in the third phase of research, to aid in exploration of healthcare providers’ determinants important for implementing and providing deprescribing regardless of their familiarization with deprescribing. Using the CHOPPED questionnaire, it was found that the majority of healthcare providers (87%) would suggest deprescribing to a patient if appropriate. For pharmacists, the most important facilitators were extrinsic factors (collaboration facilitators and healthcare facilitators factors), while for physicians intrinsic (knowledge and awareness) and patient-related factors were more prominent. Moreover, a case vignette study elucidated pharmacists can identify potential deprescribing targets and suggest deprescribing rationales which physicians would accept. Collaborative deprescribing targets should be medicines both healthcare providers share most agreement on, such as nonsteroidal anti-inflammatories (NSAID), opioids (OPI) or diuretics. In a crosssectional stud conducted in community pharmacies across Croatia, which enrolled 388 patients older than 65 years, 55.2% of participants were identified as potential candidates for deprescribing of one or more medications; 31.1% of proton pump inhibitors (PPI) users, 74.8% of NSAID, 75.0% of OPI, and 96.1% of benzodiazepine (BZN) users met at least one deprescribing criterion. Several predictive factors were identified for increased need for deprescribing, including identifying as a woman (aOR = 2.58; 95% CI =1.59 - 4.18; p < 0.001), poor self-reported health (aOR = 5.14; 95% CI = 1.73-15.25; p < 0.001), and polypharmacy (aOR = 1.29; 95% CI = 1.17 - 1.44; p < 0.001). Formative evaluation, as a result of this doctoral research, can lead to an implementation strategy facilitated by CHOPPED questionnaire and interventional protocol (Collaborating for Older aduLts to Deprescribe in primarY care” (COLDY)), proposed in this doctoral thesis, which can help engage healthcare providers in collaborative patient care with the goal of promoting deprescribing to enhance patient safety and optimise pharmacotherapy.