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Novocain (Procaine Hydrochloride Infiltration) - Description and Clinical Pharmacology

 
 



NOVOCAIN®
PROCAINE HYDROCHLORIDE INJECTION, USP

Local Anesthetic for Local Infiltration and Peripheral Nerve Block

THESE SOLUTIONS ARE NOT INTENDED FOR SPINAL OR EPIDURAL ANESTHESIA OR DENTAL USE

Rx only

DESCRIPTION

Procaine hydrochloride is benzoic acid, 4-amino-, 2-(diethylamino) ethyl ester, monohydrochloride, the ester of diethylaminoethanol and para-aminobenzoic acid, with the following structural formula:

It is a white crystalline, odorless powder that is freely soluble in water, but less soluble in alcohol and has a molecular weight of 272.78.

Composition of Available Solutions

Each mL contains

1% Ampul

1% Vial

2% Vial

[Acetone sodium bisulfite is added as an antioxidant in all products, and chlorobutanol is added as an antimicrobial preservative in the multiple-dose vials.]

Procaine hydrochloride

10 mg

10 mg

20 mg

Acetone sodium bisulfite

≤ 1 mg

≤ 2 mg

≤ 2 mg

Chlorobutanol

≤ 2.5 mg

≤ 2.5 mg

The solutions are made isotonic with sodium chloride and the pH is adjusted between 3 and 5.5 with sodium hydroxide and/or hydrochloric acid.

Procaine hydrochloride is related chemically and pharmacologically to the ester-type local anesthetics. It contains an ester linkage between the aromatic nucleus and the amino group.

NOVOCAIN is available as sterile solutions in concentrations of 1% and 2% for injection via local infiltration and peripheral nerve block.

CLINICAL PHARMACOLOGY

Local anesthetics block the generation and the conduction of nerve impulses, presumably by increasing the threshold for electrical excitation in the nerve, by slowing the propagation of the nerve impulse, and by reducing the rate of rise of the action potential. In general, the progression of anesthesia is related to the diameter, myelination, and conduction velocity of affected nerve fibers. Clinically, the order of loss of nerve function is as follows: pain, temperature, touch, proprioception, and skeletal muscle tone. Procaine lacks topical anesthetic activity.

Systemic absorption of local anesthetics produces effects on the cardiovascular and central nervous systems. At blood concentrations achieved with normal therapeutic doses, changes in cardiac conduction, excitability, refractoriness, contractility, and peripheral vascular resistance are minimal. However, toxic blood concentrations depress cardiac conduction and excitability, which may lead to atrioventricular block and ultimately to cardiac arrest. In addition, myocardial contractility is depressed and peripheral vasodilation occurs, leading to decreased cardiac output and arterial blood pressure.

Following systemic absorption, local anesthetics can produce central nervous system stimulation, depression, or both. Apparent central stimulation is manifested as restlessness, tremors and shivering, progressing to convulsions, followed by depression, and coma progressing ultimately to respiratory arrest. However, the local anesthetics have a primary depressant effect on the medulla and on higher centers. The depressed stage may occur without a prior excited stage.

Pharmacokinetics:

The rate of systemic absorption of local anesthetics is dependent upon the total dose and concentration of drug administered, the route of administration, the vascularity of the administration site, and the presence or absence of epinephrine in the anesthetic solution. A dilute concentration of epinephrine (1:200,000 or 5 μg/mL) usually reduces the rate of absorption and plasma concentration of NOVOCAIN. It also will promote local hemostasis and increase the duration of anesthesia.

Onset of anesthesia with NOVOCAIN is rapid, the time of onset for sensory block ranging from about two to five minutes depending upon such factors as the anesthetic technique, the type of block, the concentration of the solution, and the individual patient. The degree of motor blockade produced is dependent on the concentration of the solution.

The duration of anesthesia also varies depending upon the technique and type of block, the concentration, and the individual. NOVOCAIN will normally provide anesthesia which is adequate for one hour.

Local anesthetics are bound to plasma proteins in varying degrees. Generally, the lower the plasma concentration of drug, the higher the percentage of drug bound to plasma.

Local anesthetics appear to cross the placenta by passive diffusion. The rate and degree of diffusion is governed by the degree of plasma protein binding, the degree of ionization, and the degree at lipid solubility. Fetal/maternal ratios of local anesthetics appear to be inversely related to the degree of plasma protein binding, because only the free, unbound drug is available for placental transfer. The extent of placental transfer is also determined by the degree of ionization and lipid solubility of the drug. Lipid, soluble nonionized drugs readily enter the fetalblood from the maternal circulation.

Depending upon the route of administration, local anesthetics are distributed to some extent to all body tissues, with high concentrations found in highly perfused organs such as the liver, lungs, heart, and brain.

Various pharmacokinetic parameters of the local anesthetics can be significantly altered by the presence of hepatic or renal disease, addition of epinephrine, factors affecting urinary pH, renal blood flow, the route of drug administration, and the age of the patient. The in vitro plasma half-life of NOVOCAIN in adults is 40 ± 9 seconds and in neonates 84 ± 30 seconds.

NOVOCAIN is readily absorbed following parenteral administration and is rapidly hydrolyzed by plasma cholinesterase to para-aminobenzoic acid and diethylaminoethanol.

The para-aminobenzoic acid metabolite inhibits the action of the sulfonamides. (See PRECAUTIONS.)

For NOVOCAIN, approximately 90% of the para-aminobenzoic acid metabolite and its conjugates and 33% of the diethylaminoethanol metabolite are recovered in the urine, while less than 2% of the administered dose is recovered unchanged in the urine.

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