Objectives: The primary objective of the research is to determine frequency and type of therapeutic problems present at chronic and elderly patients and also frequency and types of clinical pharmacist interventions, in order to prevent medication errors and to make pharmacotherapy optimization. Another objective is to determine the level of acceptance of the proposed interventions in the prescribed treatment by a family physician. Specific objectives are to determine the suitability of the application of non-prescription (OTC) drugs and food supplements, considering the indication, dose, dosing interval, application duration and the frequency of potential clinically significant interactions with prescription drugs. Specific objective is also to identify sources of recommendations for the usage of non-prescription drugs (by doctor, pharmacist, advertisements, media, a family member, friend or acquaintance, or on the basis of own knowledge and experience). Patients and methods: This intervention study was conducted at the Family practice office Dr. Nedjeljka Grubišić- Čabo in Split, in duration of one month from 1st to 31 st of August 2013 and 91 patients were involved. In order to collect other patient data, the questionnaire and a structured interview with the patient were used. The pharmacist had the access to the patient record, from which was visible the prescribed therapy, diagnosis and laboratory findings. Inclusion criteria for patients were: older age and patients with chronic therapy, regardless the age. The interview with the patient included questionare regarding height and weight, food supplements or OTC drugs currently used, the possible use of other drugs previously prescribed to one of the family members or friends and questions about adherence. The questionare included questions about the selection of OTC drugs for symptomatic treatment. Data were collected by whose recommendation the patient takes OTC drugs. By analyzing data of the prescribed pharmacotherapy and possible automedication, potential therapeutic problems were determined. For the screening of potential clinically significant drug interactions and also drug- herbal drug or food suplement interactions, verified Lexi comp database was used, which classified moderate and highly significant interactions by the level of clinical significance C, D or X. For accuracy of prescribing regarding indications, contraindications, dosage and dosing interval, and possible adverse drug reactions, summary of medicinal product characteristics were used. Food- drug interactions were determined by using the summary of medicinal product characteristics and drug- disease interactions by using the summary of medicinal product characteristics and other professional literature. The proposal of the pharmaceutical interventions contained reference, based on which specific intervention was proposed. Data were statistically analyzed in program SPSS. Results: A total of 119 therapeutic problems were found, of wich drug interactions (75,8 %) and non-adherence (12,5 %) were most common. Drug interactions were found in therapy of 75,8 % of respondents. Most often were the interactions of degree clinical importance C, while interactions of clinical degree importance X were found in 2,2 % of patients. Food- drug interactions were found in 3,3 % of patients, drug- food supplement interactions and drug- disease interactions in 9,9 % of patients. Duplication of therapy consisted 5,9 % of the therapeutic problems. Contraindications were found within 3,3 % of patients. At 6,6 % of respondents there is a clear indication for medicine prescribing, and the doctor did not prescribe any drug. 12,5 % of therapeutic problems related to non adherence. The reasons for non adherence were fear of adverse drug reactions (60 %) and lack of knowledge about the importance of drug therapy (20 %). Adverse drug reactions were detected in 4,4 % of patients. For 3,3 % patients there was a new disease/ condition identified because of the drug usage. From total 74 pharmacist interventions aimed on doctors 75,7 % of them were accepted. The most common pharmacist intervention aimed on doctors concerned the exclusion of the prescribed drug (29,5 %), the drug substitution (21,6 %), informing doctor about non adherence patients (15,9 %) and recommendations for the additional patients monitoring (14,8 %). Changing the drug dose made 4,5 % and dosing interval changes 2,3 % of total pharmacist interventions. Pharmacist interventions aimed on patient were related to informing the patients about the drug and food supplement interactions (73,5 %). 17,6 % of interventions were related to informing patients about the proper drug usage. For the 8,9 % of respondents daily treatment schedule is made because of polytherapy. Only 6,5 % of respondents ask the pharmacist for advice in OTC use for self- medication. Most respondents (37 %) rely on their own knowledge and experience regarding drug selection for self- medication. Therapeutic problems regarding the usage of OTC drugs for self- medication were detected. Most common were drug- disease interactions (52,9 %), inadequate drug dosage (35,3 %), while OTC drug interactions with prescription drug included 11,8 % of all therapeutic problems. Conclusion: Pharmacists are highly trained health professionals, but their knowledge in practice is poorly used. There is a growing interest in support for expanding the role of pharmacists on the bases of primary health care. Pharmacotherapy optimisation, as the prevention, should have a positive impact on treatment outcomes and patient safety. In this study, a total of 119 therapeutic problems were detected. Drug interactions were found within 75,8 % of respondents and made up 27,7 % of therapeutic problems. Of total 74 pharmacists interventions aimed on doctors 75,7 % of them were accepted, and most often referred to exclusion of prescribed therapy. Most of the pharmacist interventions aimed on patient referred to informing about drug- food supplement interactions (73,5 %). While pharmacists are the most accessible health care professionals, this study has shown that only 6,5 % of respondents ask the pharmacist for OTC advice about self- medication. Most respondents (37 %) rely on their own knowledge and experience regarding drug selection for self- medication. Further research on larger sample, and through longer period in order to trace the effects of clinical pharmacist interventions on improving therapeutic outcomes and pharmacoeconomic effects of such interventions.