Clinical practice with antidementia drugs in a geriatric clinic

Cholinesterase inhibitors and N-methyl-D-aspartate antagonist have been used increasingly for patients with dementia. However these products are relatively costly and have been linked to many adverse events. Only a few surveys of prescribing patterns of drugs for dementia have been conducted in developing countries, while the proportion of dementia patients is expected to become higher in these regions. We aim to evaluate the utilization patterns, adverse events, and cost of antidementia drugs in a geriatric clinic at Siriraj hospital.

Data was obtained from the medical records of dementia patients who were newly diagnosed between January 2007 and December 2009 in the Geriatric clinic, Siriraj hospital, Bangkok. The diagnosis was based on DSM-IV (Diagnostic and Statistical Manual of Mental Disorders-IV) criteria.

Ninety-six elderly patients were diagnosed with dementia during the studied period. Eighty patients (83.30%) with the average age of 80.6 (SD = 7) years received antidementia drugs. Donepezil was the most frequently prescribed drug (70%), followed by rivastigmine (22.5%). Concomitant use of interacting drugs was noted in 41.3% of patients. The average prescribed daily dose of rivastigmine, galantamine and memantine were lower than their effective defined daily dose. The highest average cost per year was galantamine (60,020.5 baht/year) and the lowest one was memantine (45,857.7 baht/year). Among cholinesterase inhibitors receivers, 43.5% had at least one adverse event. Thirty-seven percent of these were gastrointestinal side effects. Only 12.5% of memantine-receivers developed adverse events. One-year drug discontinuation rates were 26.1% and 12.5% in cholinesterase inhibitor and memantine groups, respectively. From multivariate logistic regression analysis, the only factor associated with adverse drug events was the presence of behavioral and psychological symptoms.

The majority of dementia patients in our study were prescribed antidementia drugs. Half of them developed adverse events, but one-year drug discontinuation was relatively low. The average daily doses were lower than recommended doses. Future prospective studies should be performed to determine the cost-effectiveness and establish evidence-based practice guideline for management of dementia patients.