Long-term experience with clozapine in Denmark: research and clinical practice.

In Denmark, the use of clozapine has increased markedly (15-25% per year) since 1983, when the drug was relaunched--after its withdrawal in 1975. Several factors have contributed to this development: 1) the interesting pharmacology of clozapine, especially the atypical influence on dopamine transmission, including a relatively high D-1/D-2 receptor affinity ratio, 2) the potent anti-anxiety and anti-psychotic effect in severe and otherwise therapy-resistant psychotic patients, and 3) the lack of extrapyramidal side effects. A special monitoring form (for registration of total and differential leucocyte counts, ECG, body weight, drugs, doses and reason for possible withdrawal of the clozapine) is used in most Danish psychiatric institutions. This form secures the regular control of vital parameters and serves as an instrument for surveys of the use of clozapine in Denmark. Also, more selective studies are being carried out, e.g., on the effect of clozapine monotherapy versus combined therapy, and on the influence of clozapine on cardiovascular functions, including left ventricular output (echocardiography).