Levobupivacaine (CHIROCAINE®) is a (S)-enantiomer of bupivacaine and it is related chemically and pharmacologically to the amino amide class of local anesthetics. Local anesthetics block the generation and the conduction of nerve impulses by increasing the threshold for electrical excitation in the nerve, by slowing 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: 1) pain, 2) temperature, 3) touch, 4) proprioception and 5) skeletal muscle tone. Levobupivacaine (CHIROCAINE®) is a safer alternative for regional anesthesia than bupivacaine. It demonstrated less affinity and strength of depressant effects onto myocardial and central nervous vital centers in pharmacodynamic studies, and a superior pharmacokinetic profile.

Ropivacaine is a member of the amino amide class of local anesthetics and is supplied as the pure S-(-)-enantiomer. It produces effects similar to other local anesthetics via reversible inhibition of sodium ion influx in nerve fibers. Ropivacaine is less lipophilic than bupivacaine and is less likely to penetrate large myelinated motor fibers, resulting in a relatively reduced motor blockade. Thus, ropivacaine has a greater degree of motor-sensory differentiation, which could be useful when the motor blockade is undesirable. The reduced lipophilicity is also associated with decreased potential for central nervous system toxicity and cardiotoxicity. Ropivacaine is indicated for the production of local or regional anesthesia for surgery and for acute pain management.

(R)-Ropivacaine (Dextroropivacaine) is a voltage-dependent potassium channel blocker with local anesthetic activity. (S)-Ropivacaine is a medication used for the production of local or regional anesthesia for surgery and for acute pain management. Ropivacaine shows a difference in channel blockade between two enantiomers, and R-Ropivacaine shows greater cardiotoxicity than (S)-Ropivacaine. (R)-Ropivacaine is the impurity in commercial formulations of Ropivacaine.