Phentolamine

The mechanism by which phentolamine accelerates reversal of soft-tissue anesthesia and the associated functional deficits is not fully understood. Phentolamine mesylate produces an alpha-adrenergic block of relatively short duration resulting in vasodilatation when applied to vascular smooth muscle. In an animal model, phentolamine increased local blood flow in submucosal tissue of the dog when given after an intraoral injection of lidocaine 2% with 1:100,000 epinephrine.

Following administration, phentolamine is 100% available from the submucosal injection site and peak concentrations are achieved 10-20 minutes after injection. Phentolamine systemic exposure increased linearly after 0.8 mg compared to 0.4 mg intraoral submucosal injection. The terminal elimination half-life of phentolamine in the blood was approximately 2-3 hours.

Pediatrics

Following administration, the phentolamine C_max was higher (approximately 3.5-fold) in children who weighed between 15 and 30 kg (33 and 66 lbs) than in children who weighed more than 30 kg. However, phentolamine AUC was similar between the two groups. It is recommended that in children weighing 15-30 kg, the maximum dose of phentolamine should be limited to ½ cartridge (0.2 mg).

The pharmacokinetics of phentolamine in adults and in children who weighed more than 30 kg (66 lbs) are similar after intraoral submucosal injection.

Phentolamine has not been studied in children under 3 years of age or weighing less than 15 kg (33 lbs). The pharmacokinetics of phentolamine after administration of more than 1 cartridge (0.4mg) has not been studied in children.