Background: Tertiary hospitals have multiple specialist outpatient clinics attended by patients suffering from various comorbid diseases. This results in individuals attending more than one clinic per month, since dedicated clinic days are seldom on the same day. As patients attend discrete clinics, they have separate encounters with various prescribers, increasing the potential for irrational drug use. In addition, multiple clinic visits have a negative socio-economic impact on health care users from poorer communities where financial resources are limited due to transport expenses and days of work missed. The aim of this study was to determine the prescribing pattern of drugs to chronic disease outpatients, and find possible solutions to provide a system that would reduce overprescribing of chronic medication at Steve Biko Academic Hospital (SBAH) in one measure namely drug duplication. Methods: A retrospective descriptive cross-sectional study with the use of convenience sampling was employed to determine the medication prescribing practises to comorbid chronic disease patients attending multiple specialist clinics at SBAH from February 1, 2018-May 31, 2018. Participants were selected according to their appearance in the hospital records, with sample saturation reached when each participant had visited all the different clinics. Chronic disease outpatients attending the SBAH clinics had reviews every three months. The reviews were controlled by issuing patients with medication for a three-month period, where after a follow up visit was mandatory in order to ensure prescription and medication renewal. Therefore, each patient visited all the clinics rendering a service relating to a specific chronic condition within a four-month period that determined the study period chosen. Hospital records of patients attending the most frequently visited clinics as reported by the SBAH Pharmacy and Therapeutics committee (PTC) were evaluated. These clinics included outpatient departments of diabetes, haematology, internal medicine, neurology, oncology and psychiatry. Each drug prescription observed was evaluated using guidelines of World Health Organization (WHO) titled, “How to investigate drug use in health facilities: selected drug use indicators.” Prescribing indicators relevant to this study were used from the WHO guidelines. Results: One hundred and six patients were multiple clinic-attendees during the study period. Of the 106 patients retained, 103 (97.17%) patients attended two clinics and three (2.83%) patients attended three clinics. Regarding the WHO prescribing indicators, the average number of visits to SBAH by the comorbid chronic disease outpatients observed was 3.03 visits during the four-month study period. Prescription analysis included 80 (75.47%) patients out of 106 patients attending multiple clinics at the same time. The average number of drugs prescribed per encounter was 4.97. The results also showed that 45.45% of the 187 prescriptions observed contained five or more drugs. Most frequently prescribed drugs were tramadol 51 (5.49%), followed by simvastatin 48 (5.17%) and enalapril 45 (4.84%). Drug duplication occurred in 68 individual cases in the 80 patients observed. In total, drug duplication affected 39 patients (48.75%) [95% CI = 37.80%: 59.70%]. The most duplicated drug classes were analgesics 18 (26.47%), followed by anti-depressants 14 (20.59%) cases recorded. Conclusion: The results from this study support findings from similar studies at different institutions. The study confirmed multiple clinic visits are prevalent in the medical disciplines, often prescribing drugs from the same class. Clinical implications from these frequent and separate encounters may result in irrational prescribing, adverse drug events, drug-drug interactions and polypharmacy. The establishment of polypharmacy to comorbid chronic disease patients indicates the high risk of drug-drug interactions and adverse drug events. A prospective study would have provided more data for analysis to determine the level of polypharmacy and drug duplication. Thus, supplementation of this study with further studies could provide conclusions on whether the patients suffered from problematic or had appropriate polypharmacy. Physicians treating multiple clinicattendees should be equipped to monitor rationality of prescribing encounters. Installation of an advanced electronic Hospital Information System (HIS) could aid in improving drug prescribing in tertiary hospitals. Use of electronic prescribing tools as shown in previous studies is a requirement to improve tertiary hospitals in developing countries such as SBAH. The incidence of drug duplication at SBAH builds on existing evidence of unnecessary healthcare costs because of medication errors. / Dissertation (MSc)--University of Pretoria, 2020. / Pharmacology / MSc (Pharmacology) / Unrestricted