[Heart rate behavior and the ischemic ST-segment under carteolol hydrochloride. Dose-response relationship and duration of effect].

1. The dose-response relation and duration of action of the beta-blocking agent 5-(3-tert-butylamino-2-hydroxy-propoxy)-3,4-dihydro-2(1H)-quinolinone hydrochloride (carteolol hydrochloride, Endak, Endak mite) were investigated by means of exercise testing under randomized, double-blind conditions in two groups of healthy probands (n = 9 and n = 9, respectively). 2. The effect of 2 mg carteolol p.o. on changes in heart rate, ischemic ST-segment depression, and blood pressure was studied in 10 patients with coronary heart disease using an exercise test performed 2 h after ingestion of the drug. 3. In terms of exercise heart rate, a clear dose-response relation was demonstrated over the range of dosages (1 and 5 mg) employed. Exercise heart rate was reduced by 10% after a single dose of approximately 0.5 mg. The beta-blocking effect of 0.2 mg carteolol, however, remains unconfirmed. A dosage increase from 5 to 25 mg yields only a slight additional effect. The therapeutically attainable maximal reduction in the rise in exercise heart rate should be about 20%. 4. 24 h after a single dose of carteolol, 60-90% of the initial drug effect was still evident. 5. Resting and standing heart rate were not influenced significantly by 1, 2, 5 or 25 mg carteolol. The groups displayed a somewhat variable response. 6. 2 h after intake of 2 mg carteolol, mean ischemic ST-segment depression was reduced by somewhat more than 50%. Blood pressure at rest remained unchanged, whereas the rise in systolic blood pressure during exercise was lowered significantly. 7. In comparison with other beta-blocking agents, carteolol was effective at low dosage levels and retained considerable potency 24 h after ingestion. In many cases, once--daily administration should be adequate to yield a satisfactory clinical response.