Pharmacotherapeutic group: Anaesthetic
ATC Vet Code: QN01BA52
Procaine (p-aminobenzoyl-diethyl aminoethanol) is an amino ester. Procaine, a local anaesthetic shares with other chemical families the ability to act as a membrane stabiliser, by interfering with the ability of excitable cells to generate or transmit impulses. Procaine blocks conduction by decreasing or preventing the large transient increase in the permeability of excitable membranes to Na+ that is produced by a slight depolarisation. The action of local anaesthetics is due to their direct interaction with voltage sensitive Na+ channels.
Adrenaline is composed of two major constituents, the aromatic portion of the molecule consists of 1,2-dihydroxybenzene (catechol), the aliphatic portion consists of ethanol-amine.
The duration of the action of local anaesthetics is proportional to the time which they are in actual contact with nervous tissue. Consequently procedures which localise the drug at the nerve greatly prolong the period of anaesthesia. It has been demonstrated that the addition of epinephrine to local anaesthetic solutions greatly prolongs and intensifies their action. Epinephrine performs a dual service. By decreasing the rate of absorption it not only localises the anaesthetic agent at the desired site but also allows the rate at which the anaesthetic is destroyed in the body to keep pace with the rate at which it enters the circulation. This greatly reduces systemic toxicity.
Procaine Hydrochloride is a local anaesthetic. The in-vitro half-life of in plasma is less than 1 minute. It is only slightly bound to plasma protein (5.8%) and has a duration of anaesthetic effect of about 50 minutes in man. Adrenaline is added to local anaesthetics such as Procaine Hydrochloride to slow diffusion and limit absorption as it constricts arterioles and capillaries, so prolonging the duration of the effect and lessening the danger of toxicity.