Hospitalisation for adverse events related to drug therapy: incidence, avoidability and costs.

OBJECTIVES: To determine the incidence of hospital admissions for adverse events related to drug therapy, and to assess whether these drug-related admissions (DRAs) could have been reasonably prevented. SETTING: A tertiary teaching hospital. DESIGN AND PATIENTS: Prospective assessment of all admissions through the emergency department and resulting in a stay of more than 24 hours during 30 consecutive days in November and December 1994 to determine if the admission was related to drug therapy. Cases of intentional overdose were excluded. MAIN OUTCOME MEASURES: The number, type, causality and avoidability of drug-related admissions. RESULTS: Of 965 admissions, 55 (5.7%) were assessed as being drug-related. Drug-related admissions (DRAs) were designated possibly (38%), probably (46%) or definitely (16%) drug-related; caused by prescribing factors (26%), patient noncompliance (27%) and adverse drug reactions (47%); and classified as definitely (5.5%), possibly (60.0%) and not (34.5%) avoidable. The estimated annual cost to the hospital for all DRAs was $3,496,956 and for unavoidable DRAs was $1,629,494. CONCLUSION: The DRA rate we found lies around the middle of the range of other published rates. Few DRAs were judged definitely avoidable and over one-third were unavoidable. Nevertheless, the largest proportion were judged possibly avoidable. As the drugs identified in this study are clearly needed in the community, efforts to reduce DRAs must concentrate on education, counselling and monitoring of drug therapy.

Prepreparatory interval effects on redundancy deficit reaction time patterns in schizophrenic and normal subjects using the embedded-set procedure.

The relative influence of genuine "redundancy deficit" and the artifactual effects of prepreparatory interval on measures of the redundancy deficit reaction time pattern (faster reaction time on trials with long preparatory intervals when the interval is of predictable vs. unpredictable length) was investigated in a study using the "embedded-set" procedure. Twenty normal and 20 schizophrenic subjects received two series of reaction time trials containing embedded sets (blocks) of four isotemporal 1-, 3-, and 7-second trials. The 7-second blocks (the blocks of interest for the calculation of redundancy deficit) were preceded by long prepreparatory intervals in one condition and by short intervals for the second. Each subject received both conditions, with the orders counterbalanced. The results indicated redundancy deficit for both schizophrenics and normals with short prepreparatory intervals, but in neither group with long prepreparatory intervals. This suggests that redundancy deficit in the embedded-set procedure (which is normally heavily biased with short prepreparatory intervals) may be more related to the enhancing effect of short prepreparatory intervals on the first (unpredictable) trial of the set than to impaired performance on the fourth (predictable) trial. The finding of similar effects in both schizophrenic and normal subjects raises questions about the specificity of redundancy deficit to schizophrenic reaction time performance. The results were discussed with reference to the original "long run" reaction time procedure for studying the same phenomenon, and theoretical issues related to the interpretation of results from the two procedures were considered.

Intensity of imperative signal influences on redundancy deficit and latency in process schizophrenics.

The resilience of the redundancy deficit pattern of schizophrenic reaction time performance was explored by examining the resistance of redundancy deficit to an experimental manipulation of imperative signal intensity. Aversive levels of stimulation have been used to alter motivation and shown to normalize schizophrenic performance in other research. In this study, 20 schizophrenic patients were administered a reaction time task under conditions of usual motivation and, 1 day later, under conditions of aversive motivation induced by high decibel levels of stimulation. The redundancy deficit pattern was observed with usual motivation but not with so-called biological motivation. The results are discussed from the points of view of the utility of redundancy deficit as an index of vulnerability to schizophrenia, implications for attentional and motivational theories of schizophrenia, and finally, in terms of the more general role of aversive stimulation in schizophrenic deficit. The finding that redundancy deficit is ameliorated by aversive motivation is consistent with theories suggesting that schizophrenics respond primarily to negative motivation. Garmezy's suggestion that the common denominator of the multiplicity of schizophrenic deficits may lie in motivational factors, particularly the prepotent avoidance motive, is supported by these results.