The use of antibiotics in the treatment of established infections for inhibiting or abolishing the growth of microorganism is very common. The risks related to their use include side effects, drug resistance and potential drug-drug interactions. A structured questionnaire was applied to patients in order to collect information about their understanding of the treatment and of how to use the antibiotic. As to the profile of the patients, 38.3% are younger than 18 years and most are females. One third does not understand the diagnosis or prescribed dosage and most of the patients had consulted with the general practitioner. Prescriptions of generic drugs continue rare, probably due to the physicians' resistance to prescribe this kind of medication. About 8% of prescriptions involved drug-drug interactions. Many treatments are compromised due to the lack of information provided to the patient or to drug-drug interactions. The efficiency of a treatment depends on all health professionals involved, who need to be adequately trained for providing effective pharmacy care.