Background: Few studies have evaluated drug-related problems in patients undergoing elective total hip or knee arthroplasty. Objective: To quantify, for patients undergoing elective total joint arthroplasty, drug-related problems arising from medication orders written before or immediately after the surgery. The primary outcome was the proportion of patients with at least one drug-related problem. The secondary outcomes were the total number and descriptions of these problems, according to the patient’s age and the category, type, and severity of the drug-related problem. Methods: From among patients who underwent elective total joint arthroplasty in a large Canadian regional health authority in 2005, 150 were randomly selected for this chart audit. Patients were included if they had been taking more than one medication before surgery. The charts were examined for drug-related problems, which were categorized according to whether the problem involved a prescription for a home medication, an order for a postoperative medication, or a potential indication for drug therapy. The problems were further described by type and potential severity. Results: Of the 146 patients whose charts were available, 116 (79.5%) had at least one drug-related problem, with a mean of 1.88 drug-related problems per patient. Of the 146 patients, 88 (60.3%) had at least one drug-related problem involving a home medication, 34 (23.3%) had problems related to postoperative orders, and 37 (25.3%) had problems related to a potential indication. The mean number of drug-related problems per patient was 2.03 for those 65 years of age or older and 1.56 for those younger than 65 years (p = 0.09); however, more of the older patients experienced at least one drug-related problem related to home medications (67% [67/100] versus 46% [21/46], p = 0.02). The most common types of problems were medication omissions, illegible drug orders, inappropriate dose or frequency, and drug–allergy interactions. Of the 275 drug-related problems identified, 147 (53.5%) were deemed potentially harmful, 78 (28.4%) required monitoring, and 50 (18.2%) were considered not harmful. Conclusions: In this study, patients who underwent total joint arthroplasty experienced many drug-related problems. Pharmacists may have opportunities to optimize patient care by identifying, resolving, and preventing drug-related problems in this patient population. RESUME Contexte : Un nombre limite d’etudes ont evalue les problemes relies a la pharmacotherapie chez les patients devant subir une arthroplastie par prothese totale de la hanche ou du genou. Objectif : Quantifier, chez les patients devant subir une arthroplastie par prothese totale non urgente, les problemes relies a la pharmacotherapie decoulant des ordonnances de medicaments redigees avant ou immediatement apres l’intervention. Le principal parametre d’evaluation etait la proportion de patients presentant au moins un probleme relie a la pharmacotherapie. Les parametres d’evaluation secondaires etaient le nombre total de ces problemes et leurs descriptions, en fonction de l’âge du patient ainsi que de la categorie, du type et de la gravite du probleme relie a la pharmacotherapie. Methodes : Parmi les patients qui avaient subi une arthroplastie par prothese totale non urgente au sein d’une importante regie regionale de la sante canadienne en 2005, 150 ont ete choisis au hasard pour cet audit sur dossiers medicaux. Les patients etaient retenus aux fins de l’audit s’ils avaient pris plus d’un medicament avant l’intervention. Les dossiers medicaux ont ete analyses a la recherche de problemes relies a la pharmacotherapie classes selon que le probleme impliquait une ordonnance pour un medicament pris a la maison, une ordonnance pour un medicament postoperatoire, ou une indication potentielle pour une pharmacotherapie. Les problemes ont ete classes plus finement par type et par gravite potentielle. Resultats : Des 146 patients dont les dossiers medicaux etaient disponibles, 116 (79,5 %) presentaient au moins un probleme relie a la pharmacotherapie, pour une moyenne de 1,88 probleme relie a la pharmacotherapie par patient. Des 146 patients, 88 (60,3 %) presentaient au moins un probleme relie a la pharmacotherapie impliquant un medicament pris a la maison, 34 (23,3 %) presentaient des problemes relies aux ordonnances postoperatoires, et 37 (25,3 %) presentaient des problemes relies a une indication potentielle. Le nombre moyen de problemes relies a la pharmacotherapie par patient etait de 2,03 pour les patients de 65 ans ou plus, et de 1,56 pour les patients de moins de 65 ans (p = 0,09); cependant, un plus grand nombre de patients plus âges ont presente au moins un probleme relie a la pharmacotherapie impliquant un medicament pris a la maison (67 % [67/100] contre 46 % [21/46], p = 0,02). Les types de problemes les plus courants etaient les omissions de medicaments, les ordonnances illisibles, les doses ou les frequences d’administration inappropriees et les interactions medicament-allergie. Des 275 problemes relies a la pharmacotherapie recenses, 147 (53,5 %) ont ete juges potentiellement nocifs, 78 (28,4 %) ont necessite une surveillance, et 50 (18,2 %) ont ete juges non nocifs. Conclusions : Les patients qui ont subi une arthroplastie par prothese totale dans le cadre de cette etude presentaient de nombreux problemes relies a la pharmacotherapie. Les pharmaciens pourraient avoir des occasions d’optimiser les soins aux patients s’ils sont en mesure de reperer, de resoudre et de prevenir les problemes relies a la pharmacotherapie dans cette population de patients.