[What are the reasons for patient preference? A comparison between oral and subcutaneous administration]

Background: Today there are different subcutaneous and three oral applicable medications for prevention of venous thromboembolism after knee and hip replacement. It is a general opinion that patients will prefer oral administration. However, until today there has been no study that analysed patient preferences and motives for deciding on the kind of administration. These data would be of interest since the consideration of patient preferences could improve adherence. The present study analysed patient preferences regarding oral or subcutaneous administration of medication after elective hip or knee replacement surgery. The results will have implications for clinical practice and for decision-making concerning the kind of administration.

Material and methods: This prospective, multi-centric, observational study was conducted in six emergency hospitals and six rehabilitation hospitals. 178 current hip and knee replacement patients undergoing thromboprophylaxis and at least one further oral medication were interviewed. Subjective assessment data of patients were collected on study-specific questionnaires (epidemiological data, amount and background of general oral medication, details on subcutaneous thromboprophylaxis, preference of administration, causes for preference).

Results: 71.91 % of the interviewed patients preferred the daily intake of a tablet, whereas only 14.61 % favoured the daily subcutaneous injection. Main causes for the preference of oral administration were easier (86.6 % of nominations) and less complex (73.1 % of nominations) handling. 70.9 % reported that one more oral application would be unproblematic. Painlessness of oral administration was relevant for 65.7 %. Causes for preferring subcutaneous administration were "safety" (55.3 % of nominations) and an assumption of a generally better effectivity of subcutaneous (47.4 % of nominations) administration. Subjective discomfort induced by subcutaneus administration increased with the time interval since surgery. Less than 5 % of patients prefer subcutaneous administration due to the high volume of their existing oral medication.

Conclusion: Patient approval of oral administration is governed by practical and comfort issues. In general, patients on existing oral medications are uncritical concerning a temporary additional oral medication. The clear discomfort measured in association with subcutaneous administration supports the idea that the oral route will have advantages for patient adherence. In particular this is of relevance with increasing time interval since surgery. Patients who have a very high volume of oral medications will probably profit from subcutaneous administration. The main reasons that patients gave for the preference of subcutaneous administration are based on incorrect knowledge. Therefore it is necessary to improve patient education concerning the existing alternatives for thromboprophylaxis.