1. The pharmacokinetics and pharmacodynamics of verapamil administered via the oral and sublingual routes were compared in a randomised, two‐ way cross‐over study involving six healthy male volunteers. 2. Administered sublingually, a verapamil 40 mg (Securon) crushed tablet produced a significantly higher peak plasma concentration (P less than 0.05), a greater rate of absorption (P less than 0.05), and greater bioavailability (P less than 0.05) when compared with orally administered verapamil 40 mg (Securon). 3. In comparison with oral dosing, PR intervals were significantly (P less than 0.05) prolonged between 30 and 90 min after sublingual verapamil dosing. 4. Correlations between log plasma verapamil concentration and percentage increase in PR interval were greater after sublingual compared with oral dosing in all volunteers.

The antiarrhythmic properties of sublingual verapamil were investigated in seven patients with acute fast atrial flutter (n = 2) or fibrillation (n = 5). A rapid and significant (P < 0.05) reduction in the ventricular rate was achieved in all seven patients. The ventricular rate at peak plasma verapamil concentration (± s.d.) was significantly slower than on admission (101.6 ± 11.3 and 159 ± 5.3 beats min-I respectively, P < 0.01). The ventricular rate remained controlled for over 4 h. Sublingual verapamil was rapidly absorbed with the maximum peak plasma concentration (153.3 ± 15.5 ng ml-') being achieved after 1.21 ± 0.18 h. Side-effects of sublingual verapamil were limited to one report of a bitter taste. The sublingual administration of verapamil may provide an alternative method for the control of acute fast atrial fibrillation and flutter in selected patients.

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