Background. The outcome of electroconvulsive therapy (ECT) is affected by the placement and dose of the stimulus. In general, the ECT dose can be selected either by the dose-titration method (on which the measured seizure threshold level is based), or the method of predetermined dose (e.g. the age-based dosing and the fixed high dose method).

Methods. Seizure thresholds were measured in 50 patients with right unilateral (RUL) and in 30 patients with experimental bifrontal (BF) ECT stimulus. The ECT dose (mC) of the age-based dosing was calculated by multiplying the age (years) by 5·0 (age method) or 2·5 (half-age method). The fixed high dose was set to 378 mC.

Results. The seizure thresholds had only a moderate correlation with the age of the patients. The methods based on the predetermined dose would have led us to give patients with the lowest seizure thresholds in the RUL ECT group very high stimulus doses, up to 12 (age method) or 15 (fixed high dose method) times the individual seizure threshold. In contrast, the RUL ECT patients with the highest seizure thresholds would have received low stimulus doses down to 1·5 times (half-age method) the initial seizure threshold. In the BF ECT group the-age based dose would have been similarly dependent on the initial seizure threshold level.

Conclusion. The use of the dose-titration method is recommended, because it is the only method that allows for the individual selection of ECT stimulus dose relative to the seizure threshold.