Procaine hydrochloride

1. Chemical Nature & Name

• It is the hydrochloride salt of the organic compound procaine. The salt form makes it water-soluble and suitable for injection.

• Brand Name: The name Novocaine (originally a trademark) became so synonymous with dental anesthesia that it entered common language, much like "Kleenex" for tissues.

2. Historical Significance

• Developed in 1905 by German chemist Alfred Einhorn.

• It revolutionized surgery and dentistry by providing a safer and more effective alternative to general anesthesia for minor procedures and cocaine (which was previously used as a local anesthetic but was highly addictive and toxic).

3. How It Works (Mechanism of Action)

• It works by blocking voltage-gated sodium channels in the membranes of nerve cells.

• This prevents the influx of sodium ions, which is essential for generating and propagating electrical nerve impulses (action potentials).

• As a result, signals for pain, touch, and other sensations cannot travel along the nerve from the numbed area to the brain.

4. Key Characteristics & Uses

• Onset: It has a moderately slow onset of action (takes several minutes to become effective).

• Duration: It has a relatively short duration of effect (typically 30-60 minutes), especially when compared to modern anesthetics.

• Primary Historical Use: It was the standard anesthetic in dentistry for decades.

• Other Uses: It has been used for infiltration anesthesia (injecting directly into tissue), minor surgical procedures, and sometimes in spinal anesthesia. It also has some veterinary applications.

5. Why It Is Less Common Today

Procaine has been largely replaced by newer local anesthetics, primarily because of several disadvantages:

• Shorter Duration: Drugs like lidocaine (discovered in the 1940s), bupivacaine, and articaine last longer.

• Allergenic Potential: Procaine is an ester-type anesthetic. Its metabolism produces para-aminobenzoic acid (PABA), a compound to which some people are allergic. Amide-type anesthetics (like lidocaine) have a much lower allergy risk.

• Weaker Potency: It is less potent than its successors, requiring larger doses for the same effect.

6. Safety and Side Effects

• Common Side Effects: When used correctly, side effects are usually localized (e.g., temporary injection site pain, bruising).

• Systemic Effects/Overdose: If accidentally injected into a blood vessel or if too high a dose is used, it can cause systemic effects. Since procaine is an ester, it is rapidly metabolized in the blood by the enzyme pseudocholinesterase, which generally makes systemic toxicity less severe than with some other drugs. However, potential effects include:

  • Central Nervous System: Dizziness, nervousness, tremors, seizures.

  • Cardiovascular: Low blood pressure, slow heart rate.

• Contraindication: It should not be used in individuals with a known hypersensitivity to ester anesthetics or in those with a rare genetic deficiency of pseudocholinesterase.