The type of blocking action of Ica,L by flecainide was also investigated. A protocol similar to that described by Lee and Tsien and Delgado et al was used to investigate tonic- and use-dependence of the block. Test pulses were applied to +10 mV continuously in normal Tyrode’s solution to obtain control ICa,L amplitude, then pulsing was stopped and flecainide (either 1 mM or 100 |iM) was applied in the absence of stimulation. After 45 s to 1 min, pulsing was resumed. The level of ICa,L with each pulse in the presence of flecainide was expressed as a proportion of the control amplitude. Any decline in current with the first pulse on resuming stimulation represented a tonic block .Figure 5 shows the results of these experiments. At this concentration, therefore, there appeared to be little if any tonic blockade of ICa,L, but the current declined rapidly to a steady level within a few depolarizing pulses. Under the experimental conditions of this study, therefore, the features of inhibition of ICa,L by flecainide appeared to depend on the drug concentration used. Best quality drugs are waiting – order antibiotics online to spend less time and money.