Background Pharmaceutical interventions are a method of ensuring the efficacy and safety of treatments.

Purpose To classify pharmaceutical interventions made by a pharmacy resident in the pharmacokinetics unit of a tertiary hospital and evaluation of acceptance by the clinician.

Materials and methods For one month, The authors reviewed electronic prescriptions of drugs with a narrow therapeutic range in medical and intensive care wards. Pharmacokinetics studies were performed using the PKS software package and reports were issued to the patient's physician. Pharmaceutical interventions were classified according to the method described by Overhage et al, which measures the gravity of medication errors and the value of clinical interventions made by the pharmacist. Drug-related problems were classified according to the Granada Consensus.

Results Thirty-two patients (84% of those reviewed) were evaluated. The drugs prescribed were digoxin (55%), valproic acid (20%), vancomycin (11%), phenytoin (7%) and amikacin (7%). The authors made 29 pharmaceutical interventions (the remaining patients had drug levels within the therapeutic range), with a degree of acceptance of 93%. Interventions were classified as follows: ‘dosing error (DE) consisting of a very low dose of a drug that is not potentially life-saving’ (10/29); ‘DE consisting of a very low dose of a potentially life-saving drug’ (10/29); ‘DE resulting in potentially toxic concentrations’ (3/29); ‘inappropriate dosing interval’ (3/29); ‘clinically significant interaction requiring follow-up’ (2/29); ‘adverse events related to precautions or contraindications’ (1/29). The classification of interventions according to clinical importance were life-threatening (34%), serious (14%), and significant (52%). Drug-related problems were classified as quantitatively ineffective (20/29), qualitatively ineffective (2/29); quantitatively unsafe (4/29), qualitatively unsafe (3/29).

Conclusions Most of the patients required a pharmaceutical intervention to adjust their treatment. All interventions made had a relevant clinical impact, as they involved high-risk drugs with a narrow therapeutic range. The most common drug-related problem was quantitative inefficacy due to underdosing.