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Prilocaine and Epinephrine (Prilocaine Hydrochloride / Epinephrine Bitartrate) - Description and Clinical Pharmacology

 
 



For Local Anesthesia in Dentistry

Rx only

DESCRIPTION

Prilocaine Hydrochloride 4% with epinephrine 1:200,000 injection is a sterile, non pyrogenic isotonic solution that contains a local anesthetic agent with epinephrine (as bitartrate) and is administered parenterally by injection. See INDICATIONS AND USAGE for specific uses. The quantitative composition is shown in Table 1.

Prilocaine Hydrochloride 4% with epinephrine 1:200,000 injection contains prilocaine HCl, which is chemically designated as propanamide, N-(2-methyl-phenyl)-2-(propylamino)-,monohydrochloride and has the following structural formula:

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Epinephrine bitartrate is (-)-3,4-Dihydroxy-a-[(methylamino)methyl] benzyl alcohol and has the following formula:

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

The specific quantitative composition is shown in Table 1.

TABLE 1. COMPOSITION
Ingredients
      Prilocaine HCl       
  Epinephrine  
   Citric Acid  
   Sodium Metabisulfite  
       pH
Formula (mg/mL)
       40.0 mg/mL
  0.005 mg/mL
  0.2 mg/mL
        0.5 mg/mL
  3.3 to 5.5 

Note: Sodium hydroxide or hydrochloric acid may be used to adjust the pH of Prilocaine Hydrochloride  4% with epinephrine 1:200,000 injection.

CLINICAL PHARMACOLOGY

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 2.25 hours.

When used for inferior alveolar nerve block, the time of onset averages less than three minutes with an average duration of soft tissue anesthesia of approximatelty 3 hours.

Hemodynamics

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 and/or the beta-adrenergic receptor stimulating of epinephrine.

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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