[Pharmacological interactions in patients treated with oral anticoagulants in a rural health area]

To estimate the prevalence of drugs that interact with oral anticoagulants and establish relationships between variables and haemorrhagic complications.

Longitudinal, retrospective study of patient anticoagulant.

Colmenar basic health area, Malaga, Spain.

Patients on anticoagulants followed up in primary care.

Indications, time of follow-up, value of last prothrombin time (INR), complications and therapeutic groups of major use.

The 74.2% of the patients had a prothrombin time (INR) in the therapeutic range; 16.14% had minor complications; 60.2% of the patients complied with the criteria of multiple medication and 88.2% complied with the criteria of multiple medication in the last 6 months. The drugs used with a higher capacity to interact are: anti-ulcer (26.9%), locomotor system (10.7%), cardiovascular drugs (2.2%), lipid lowering drugs (8.6%), and antidiabetics (17.2%). The number of drugs used in the last 6 months is associated with the presence of haemorrhagic complications (odds ratio [OR], 1.10). Allopurinol and pantoprazole had a significant relationship with the presence of minor haemorrhages (OR, 19.25 and 7.37, respectively). The variables associated with the presence of a haemorrhage were: allopurinol (OR, 25.84), number of controls with an INR outside the therapeutic range in the last 6 months (OR, 1.31) and time on treatment (OR, 1.07).

The percentage of patients within the therapeutic range in the last determination of INR indicates good quality. The number of minor complications exceeded the consensus standard for the control of patients on anticoagulants. The use of drugs with a higher capacity for interacting with oral anticoagulants was very high in the anti-ulcer and antidiabetic groups. Pharmacological control of patients on anticoagulants is necessary and multiple medications should be avoided.