Introduction
High blood pressure is the most common cause of cerebral stroke and kidney failure in the elderly, which does not require advanced equipment to control it; it can be easily controlled by taking medicine. However, the critical point in this context is the medication non-adherence and its incorrect use or non-use, which can lead to unfortunate consequences, such as more hospitalizations, increased healthcare costs, low quality of life, reduced physical performance, and advanced cognitive disorders. The use of models is a suggestion to help improve medication adherence. Since the lack of care and failure of the elderly are the crucial reasons for the medication non-adherence, these models should be accompanied by targeted action, patterned behavior, and feedback. Therefore this study aims to determine the effect of the Johnson model-based program on medication adherence of the elderly with high blood pressure. 
Methods
 The present study was a randomized controlled clinical trial with a two-group and three-stage design. The statistical population included all elderly people with high blood pressure who were referred to three bases of the Shahid Aval comprehensive health service center of Isfahan City, Iran in 2019. A total of 70 people were selected based on the inclusion criteria, including diagnosis of high blood pressure by a specialist doctor of the confirmed center and undergoing treatment, not suffering from known mental illnesses, not smoking and other tobacco products, non-participation of the elderly in family-oriented programs in the last three months, access to fix phone or cell phone at home, familiarity with Farsi language and they were allocated in two intervention and control groups. Data collection tools were a Riester Nova 1032 mercury sphygmomanometer made in Germany, a stethoscope, an elderly blood pressure registration checklist, a needs assessment questionnaire, and demographic characteristics questionnaire of the research units. For the intervention test group, a program based on Johnson’s model was implemented once a week. For this purpose, the model of medication adherence consisting of three concepts of targeted action, patterned behavior, and feedback was used. The intervention in this study was conducted by focusing on the concepts of the adherence model as a combination of group meetings, group discussions, face-to-face interviews, lectures, giving educational booklets, and home visits. In addition to the elderly, an active family member (informal caregiver) also participated in the meetings. The first 3 sessions focused on the concept of purposeful action (perceived need, perceived effectiveness, perceived safety), and the fourth session focused on the concept of patterned behavior (access, routine, reminder). The meetings were held in groups of 5 to 6 people and in the meeting hall of the center every week for a period of 30 to 60 minutes. The third concept (feedback) was carried out during 2 home visit sessions. Data were analyzed with SPSS22 statistical software using independent t test, chi-square, and repeated analysis of variance (ANOVA).
Results
The results of the study showed that the two groups had no significant statistical differences in terms of demographic characteristics. According to the purpose of the study, the mean systolic and diastolic blood pressure of the two groups at the beginning of the study did not have a statistically significant difference (P<0.05). Immediately after the implementation of the intervention and also after 3 months of follow-up in the intervention group, it decreased significantly (P<0.05). Also, the repeated measurement analysis of variance (ANOVA) showed that in the test group, systolic and diastolic blood pressure had a decreasing trend in three times (P<0.001) but in the control group, the trend of changes in the mean systolic blood pressure increased significantly, and regarding diastolic blood pressure, despite the significant decrease in the post-test time, but three months, no significant difference was observed (P=0.63) (Table 1). 


Discussion
 Family-based medication adherence program based on Johnson’s model is effective in reducing blood pressure in the elderly with hypertension, and this means that this medication plan as a nursing intervention and an easy, low-cost, and accessible method can be vital in the medication program of these elderly people. Many elderly people and their families still have little information on the disease and its complications, despite passing a lot of time from the disease, and they do not follow the prescribed medication. In line with the comprehensive nurse and considering the importance of the role of the family in the treatment of the patient, it is necessary to pay attention to the education of the family in nursing care; hence training by the personnel of the pharmaceutical health service system, especially nurses, will be very helpful.

Ethical Considerations
Compliance with ethical guidelines
Ethical principles are fully observed in this article. Participants were allowed to withdraw from the study whenever they wanted. Also, all participants were aware of the research process. Their information was kept confidential. Also, all ethical principles have been approved by the Ethical Committee of Isfahan University of Medical Sciences (Code: IR.MUI.RESEARCH.REC.1398.410). 

Funding
This study is part of a thesis approved at Isfahan University of Medical Sciences, which was conducted at Shahid Aval comprehensive health services center of Isfahan. 

Authors' contributions
All authors contributed equally to the preparation of this article.

Conflicts of interest
The authors declared no conflict of interest in this article. 

Acknowledgements
We appreciate the graduate studies of the university and the sincere cooperation of the honorable director and management of the center, seniors, and valuable companions that without their cooperation, this research was impossible. 


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