Antazoline Phosphate

Antazoline phosphate acts as an imidazoline compound that inhibits voltage-gated Ca2+ channels in striatal neuronal cultures. The inhibition is fast in onset, fully reversible upon washout, and shows marked voltage dependence, with greater inhibition observed at more depolarized membrane potentials. Among the different types of voltage-gated calcium channels, antazoline predominantly blocks P/Q-type and N-type channels. The half-maximal inhibitory concentration for antazoline acting at a phencyclidine-like site on these channels was determined.
By inhibiting presynaptic P/Q-type and N-type calcium channels, antazoline reduces calcium influx into nerve terminals, thereby decreasing the release of excitatory neurotransmitters such as glutamate. This mechanism contributes to the neuroprotective effects of antazoline against hypoxic and excitotoxic neuronal injury. The calcium channel blocking activity of antazoline also helps explain its antiarrhythmic properties in converting atrial fibrillation to sinus rhythm, as calcium channel inhibition prolongs the effective refractory period of cardiac myocytes and suppresses abnormal impulse generation in the atria.

Fig. 1 Antazoline sensivity of the different Ca2+ channel subtypes in striatal neurones from 12-day primary cultures. (Milhaud D.; et al. 2002)

A case-match study compared the effectiveness of intravenous antazoline phosphate with amiodarone, flecainide, and propafenone for pharmacological cardioversion of recent-onset atrial fibrillation in the emergency department. Using propensity score matching, 33 patients receiving antazoline were matched with 33 patients receiving other antiarrhythmics. Antazoline achieved successful sinus rhythm restoration in 63.6 percent of patients compared to 61.3 percent for other antiarrhythmics, with no statistically significant difference in efficacy. However, the mean time to restore sinus rhythm was significantly shorter with antazoline compared to other agents, representing a 3.8-fold faster conversion. These findings confirm that antazoline phosphate offers a rapid-acting alternative for acute conversion of atrial fibrillation in emergency settings.

Fig. 2 Demographic and clinical parameters of the patients included in the case-match analysis. (Springer J.; et al. 2024)