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Citanest Plain (Prilocaine Hydrochloride Dental) - Description and Clinical Pharmacology


For Local Anesthesia in Dentistry

Rx only


4% Citanest Plain Dental (prilocaine HCl Injection, USP), is a sterile, non pyrogenic isotonic solution that contains a local anesthetic agent and is administered parenterally by injection. See INDICATIONS AND USAGE for specific uses. The quantitative composition is shown in Table 1.

4% Citanest Plain Dental contains prilocaine HCl, which is chemically designated as propanamide, N-(2-methyl-phenyl) -2- (propylamino)-, monohydrochloride and has the following structural formula:

C<sub>13</sub>H<sub>20</sub>N<sub>2</sub>O ∙ HCl     molecular wt = 256.77

C13H20N2O ∙ HCl     molecular wt = 256.77

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration.

The specific quantitative composition is shown in Table 1.

Product Identification Formula (mg/mL)
Prilocaine HCl pH
4% Citanest Plain Dental 40.0 6.0 to 7.0

Note: Sodium hydroxide or hydrochloric acid may be used to adjust the pH of 4% Citanest Plain Dental Injection.


Mechanism of Action

Prilocaine stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses, thereby effecting local anesthetic action.

Onset and Duration of Action

When used for infiltration injection in dental patients, the time of onset of anesthesia averages less than 2 minutes with an average duration of soft tissue anesthesia of approximately 2 hours.

Based on electrical stimulation studies, 4% Citanest Plain Dental Injection provides a duration of pulpal anesthesia of approximately 10 minutes in maxillary infiltration injections. In clinical studies, this has been found to provide complete anesthesia for procedures lasting an average of 20 minutes.

When used for inferior alveolar nerve block, the time of onset of 4% Citanest Plain Dental Injection averages less than three minutes with an average duration of soft tissue anesthesia of approximately 2½ hours.


Excessive blood levels may cause changes in cardiac output, total peripheral resistance, and mean arterial pressure. These changes may be attributable to a direct depressant effect of the local anesthetic agent on various components of the cardiovascular system.

Pharmacokinetics and Metabolism

Information derived from diverse formulations, concentrations and usages reveals that prilocaine is completely absorbed following parenteral administration, its rate of absorption depending, for example, upon such factors as the site of administration and the presence or absence of a vasoconstrictor agent. Prilocaine is metabolized in both the liver and the kidney and excreted via the kidney. It is not metabolized by plasma esterases. Hydrolysis of prilocaine by amidases yields ortho-toluidine and N-proylalanine. Both of these compounds may undergo ring hydroxylation.

O-toluidine has been found to produce methemoglobin, both in vitro and in vivo (see ADVERSE REACTIONS).

Because prilocaine is metabolized in both the liver and kidneys, hepatic and renal dysfunction may alter prilocaine kinetics.

As with other local anesthetic agents, the plasma binding of prilocaine may be dependent on drug concentration. At 0.5 to 1.0 mg/mL it is 55% protein bound.

Prilocaine crosses the blood-brain and placental barriers, presumably by passive diffusion.

Factors such as acidosis and the use of CNS stimulants and depressants affect the CNS levels of prilocaine required to produce overt systemic effects. In the rhesus monkey, arterial blood levels of 20 mg/mL have been shown to be the threshold for convulsive activity.

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