Last updated: 03/04/2015
What type of Local?
Mechanism of Action
Blocks 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.
Plasma cholinesterases (just like succinylcholine), also elimination will be impaired in hepatic/renal disease.
- Cardiac depression: decrease CO, and HR, contractility, vasodilation
- CNS: seizures, depression of medulla, coma, resp depression, death
How does local anesthetic cross placenta?
- passive diffusion
- the rate and degree of diffusion are determined by:
- the degree of plasma protein binding
- since only the free, unbound drug is available for placental transfer
- protein binding: less protein binding means more transfer
- the degree of ionization: less ionization means more transfer
- lipid solubility: more fat soluble means more transfer
Effects on Fetus
- Fetal bradycardia
- heart rate of less than 120 per minute w/ doses of chloroprocaine of 120 mg to 400 mg of chloroprocaine
- effect may NOT be dose related
- Fetal acidosis
- limited data
- demonstrated by blood gas monitoring around the time of bradycardia or afterwards.
- No intact chloroprocaine and only trace quantities of a hydrolysis product, 2-chloro-4-aminobenzoic acid, have been demonstrated in umbilical cord arterial or venous plasma following properly administered paracervical block with chloroprocaine.
- The role of drug factors and non-drug factors associated with fetal bradycardia following paracervical block are unexplained at this time.
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