Polymedication and medication compliance in patients with chronic non-malignant pain

Most reports of polymedication among patients with chronic non-malignant pain have relied only on the patient's statements which have been proven to be unreliable regarding actual drug consumption. This study investigates the incidence of polymedication and medication compliance in these patients by applying objective methods. One-hundred-nine consecutive patients predominantly with facial, neuropathic or back pain were interviewed about present medication at first admission to the pain clinic. Reports were verified by toxicological urine screening, mainly with thin-layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS) coupling. Follow-up investigations of 61 patients were conducted within 1 and 24 months after beginning therapy. Polymedication--here defined as daily intake of 3 or more preparations--was found in 41 patients (38%) in the initial investigation. In only 74 patients (68%) did the results of urine screening correspond with their reports: 23 patients (21%) concealed the consumption of drugs, and 2 patients (2%) did not take their medications. Ten cases were not interpretable. Fifty-four percent of the drugs concealed were psychotropic substances, mostly benzodiazepines, and 42% were analgesic combinations, partly with psychotropic additives. Drug intake was concealed significantly more often with polypharmacy which was occurring more frequently in patients with headache or facial pain, longer duration of pain, young age, psychiatric diagnosis and history of substance abuse. Patients with initial non-compliance were more likely to conceal drug consumption in follow-up investigations as well (P = 0.05). Therefore, screening for medication compliance in patients with chronic non-malignant pain is recommended, especially in those with the abovementioned risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)