Local Anesthetics

Prilocaine hydrochloride (Citanest)

Prilocaine is similar in action to Lidocaine and Mepivacaine, but slightly less potent and less toxic than Lidocaine, with slightly longer duration of action (pKa= 7.9). Metabolism is unusual in that de-alkylation is not required as a first step (its already a secondary amine); it’s usually a first step in the degradation of LA’s, but not in this case.

Prilocaine can cause cyanosis due to production of methemoglobin (oxidized form of hemoglobin in which ferrous is converted to ferric iron, and O2 binding affinity is drastically reduced). Should not be used in cases where oxygenation is critical, eg. pregnancy. Should not be used in conjunction with other drugs that may induce formation of methemoglobin (eg. acetaminophen or phenacetin). Its important to know that Prilocaine comes in a 4% solution both without vasoconstrictor and with vasoconstrictor (1:200,000 epinephrine).


Bupivacaine hydrochloride (Marcaine, Sensorcaine)

the structure is similar to Mepivacaine, but the methyl is replaced by C4H9, which makes it more hydrophobic and more potent. Bupivacaine is 4x as potent and toxic as Mepivacaine. The dental preparation is 0.5% solution with 1:200,000 epinephrine. Bupivacaine is the only long-acting LA currently available (others have been pulled from the market for financial reasons).

Etidocaine hydrochloride (Duranest)

The name Duranest indicates that it’s a long duration product. Etidocaine has just been pulled from the market however.

Articaine hydrochloride (Septocaine)

The structure of Articaine is not drawn on the handout, and I can’t draw it here. Just know that it is an amide LA with a thiophene rign instead of a benzene ring, and has a methyl side-group attached to the thiophene ring by an ester bond (although it has an ester bond, it is still considered an amide!!). There is a Sulfur in the thiophene ring, be careful with pts who are allergic to sulfur.
Articaine comes in 1.7 ml carps, just to be different.

Body clearance is about 20 minutes (t ½) , compared to 90-120 minutes for Lidocaine.

Remember: Articaine is a 4% solution, so you should inject less than half of what you would if you were using Lidocaine.

H1-Receptor Antagonists

Diphenhydramine (Benadryl) and Promethazine (a phenothizine) and Pyrilamine (an ethylenediamine) are all effective local anesthetics theoretically,

Category: Pharmacology Notes