By conducting the SPPA trial we try to find out, whether personalized Short Message Service (SMS) reminders of blood pressure-lowering medication can effectively increase patients' adherence to blood pressure-lowering medication. Additionally, we also evaluate their effect on patients' systolic blood pressure control.

Hypertension belongs to the main risk factors of cardiovascular diseases, which are the leading cause of morbidity and mortality in the world and in the Slovak Republic. Despite the availability of effective antihypertensive treatment, blood pressure control remains a serious problem. Poor adherence to blood pressure-lowering medication is considered to be the key factor for uncontrolled blood pressure. Studies estimate the overall adherence to medication in patients with chronic diseases at around 50%. Slovak studies report even significantly lower adherence rates (15-19%), which underlines the urgency to address this health problem in the Slovak Republic. The majority of interventions aimed at increasing patients' adherence are associated with substantial costs and health care professionals capacity, both lacking in the current Slovak health care system. Several studies have shown the efficiency of SMS reminders to improve patients' adherence and health outcomes at very low cost. Since mobile phones are frequently used among Slovak inhabitants and SMS messages are a popular mean of communication, this approach could be feasible also in Slovakia. Pharmacists are highly trained drug experts who have the knowledge, skills and time to address patients' nonadherence using a simple SMS reminder system.

Thus, our research question is as follows: Do personalized daily SMS reminders of blood pressure-lowering medication intake provided by pharmacists in addition to standard Pharmaceutical Care reduce the proportion of nonadherence to blood pressure-lowering medication among older ambulatory patients with hypertension in Slovakia? And we hypothesize that personalized daily SMS reminders of blood pressure-lowering medication intake provided by pharmacists in addition to standard Pharmaceutical Care increase the proportion of adherence to blood pressure-lowering medication among older ambulatory patients with hypertension in Slovakia from 30% to 49% in the intervention group compared to the control group.

Inclusion Criteria:

• Age ≥ 55 years (from the day of the 55. birthday inclusive)
• Diagnosis of primary (essential) hypertension (I10 according to International Classification of Diseases (ICD-10))
• Filling of blood pressure-lowering prescription(s) at trial recruitment (Visit 1)
• Duration of antihypertensive drug treatment for at least 1 year without any discontinuation
• Ownership of a mobile phone for personal use with the ability to open and read SMS
• Understanding of Slovak language on native-speaker level
• Informed consent for participation in the clinical trial and personally signed Informed Consent Form

Exclusion Criteria:

Exclusion criteria assessed prior to patient enrolment (by trial pharmacists):

• Planned hospitalisation during the trial period (3 months)
• Biological impairment affecting the ability to read the SMS (e.g. loss of vision, visual field cuts, aphasia)
• Living in the same household with another trial participant
• Participation in another clinical trial

Exclusion criteria assessed after patient enrolment (by trial pharmacists and project leader):

• Hospitalisation during the trial period
• Patient informs he/she won't be able to participate in the trial
• Withdrawal of Informed Consent

All collected data will be anonymized and made available on via Open Science Framework