Procaine

Procaine, also known as procaine hydrochloride or by the trade name Novocain, is a local anesthetic of the amino ester type. It was developed by German chemist Alfred Einhorn and introduced for medical use in the early 20th century. Procaine is used to induce infiltration and regional anesthesia, most notably in dental procedures, and has historically been employed for spinal anesthesia. It has largely been supplanted by newer amide local anesthetics in many settings, but remains in use in some regions.

Mechanism and pharmacology: Procaine works by blocking voltage-gated sodium channels on nerve membranes, preventing the initiation and propagation of action potentials in sensory and motor fibers. As an ester, it is rapidly hydrolyzed in the bloodstream by plasma cholinesterases (pseudocholinesterase) and liver enzymes to inactive metabolites, including para-aminobenzoic acid (PABA) and diethylaminoethanol. This results in a relatively short duration of action compared with many amide local anesthetics.

Onset and duration: Onset is typically within minutes after appropriate administration. The duration without vasoconstrictor is roughly 30–60 minutes, and use with vasoconstrictors such as epinephrine can prolong anesthesia and reduce systemic absorption, extending effects to about 1–2 hours depending on dose and site.

Adverse effects and safety: adverse effects resemble other ester local anesthetics and can include hypersensitivity reactions to PABA or to the drug itself. Systemic toxicity may present with CNS symptoms (tremor, dizziness, tinnitus, seizures) followed by possible cardiovascular depression if overdosed. Caution is advised in individuals with pseudocholinesterase deficiency, as hydrolysis of procaine may be prolonged. Cross-reactivity with other ester-type anesthetics is possible but not universal.