Background The lack of adherence to antiretroviral therapy(ART) is the leading cause of treatment failure. The ART has all the factors to make difficult the adherence. The authors have applied a pharmaceutical care program with the purpose of evaluating patients adherence to ART by means of questioners and interviews, as well as improving it providing information and education about their illness and treatment.

Purpose To evaluate the impact of pharmaceutical care program on adherence to ART and analyse the factors that affect it in a negative way.

Materials and methods Ambispective experimental study, with a prospective phase of 12 months, comparing ART adherence in patients in a pharmaceutical care program(n=28) versus adherence in patients not included(n=24).Adherence was measured in the experimental group, using the SMAQ validated questionnaire(Simplified Medication Adherence Questionnaire) and by means of the dispensary data management system, and it was only measured retrospectively for this last method in the control group. The socio-economic factors together with the disease characteristics were obtained from medical records and through a validated questionnaire made by Gemma's group (Grupo Español para el Estudio Multifactorial de la Adherencia). After that, The authors evaluated their influence on adherence by using a multivariate model estimated on a binary logistic regression.

Results The proportion of adherent patients was higher in the group who received pharmaceutical care (81.8%) than in the control group (68.4%)(p=0.058). It was also higher in the subgroup Q24 h for both groups, experimental (94.4%) and control (75%)(p=0.09).Considering the socio-economic variables dichotomous and binary, adhesion ratio was lower in patients who had children (p=0.045), with low education leve l (p=0.001), injecting-drug (p=0.000), smoking (p=0.000), alcohol (p=0.002) and methadone users (p=0.000),those who live with another HIV positive person (p=0.003) or who had HIV positive friends (p=0.024).

Conclusions Our pharmaceutical care program was able to increase the number of adherent patients. Given the negative influence of the social economic factors on adherence here described, it would be desirable to implement new strategies to improve adherence based on psycho-educational programs for these patients.