The present study aims to know the limits and possibilities on the instructions given by Community Health Agents – ACS on the use of drugs by families assisted by the Family Health Strategy – ESF. This is a qualitative, descriptive, exploratory and field work. We applied half-structured interviews with 15 ACS from eight units of the Family Health Strategy in a city in the southern end of Santa Catarina. Data were analysed and classified in categories. The major problems reported by ACS in the use of medications by families were related to: storage of medication; self-medication; schedule and incorrect amounts; interaction and adverse reaction of medicines; families having difficulties understanding instructions and adhesion to treatment; and the use of plant based drugs with continuous use medicine. It is suggested from the results of the research that ACS be trained for the rational use of medicines by families, and this activity may be developed by pharmacists from Family Health Support Nuclei – NASF. Pharmaceutical care in FHS requires mediation between ACS knowledge and the knowledge of families assisted, which implies attentive listening, a real dialogue, identifying the needs of families and making efforts to create bonds with the community, and the rational use of medicines.