Anesthesia Pharmacology: Local Anesthetics

Local Anesthetic Combinations

• Purpose of local anesthetic combination preparations:

  • Prolonged duration (bupivacaine (Marcaine)) and decreased time to onset (chloroprocaine (Nesacaine))

•  Concerns:

  • Chloroprocaine (Nesacaine) in the epidural space may lead to possibly reduced subsequent epidural space bupivacaine (Marcaine) analgesia efficacy during labor

    • Mechanism

      • Chloroprocaine (Nesacaine) reduces pH which decreases the amount of nonionized (active) bupivacaine (Marcaine)

  • Tachyphylaxis to the mixture (possibly secondary to local acidosis caused by low pH of the chloroprocaine (Nesacaine) solution)

    • Suggestion: increased chloroprocaine (Nesacaine) solution pH just before use may enhance chloroprocaine (Nesacaine)-mepivacaine (Carbocaine) combination efficacy

•  Toxicity is additive for local anesthetic combinations. 

Stoelting, R.K., "Local Anesthetics", in Pharmacology and Physiology in Anesthetic Practice, Lippincott-Raven Publishers, 1999, pp 158-181.