Local and Topical Anesthetics

Amino esters include procaine, chloroprocaine, tetracaine, cocaine, and benzocaine.^{[1, 2, 3, 4, 5]}

Amino amides include dibucaine, lidocaine, mepivacaine, prilocaine, bupivacaine, levobupivacaine, ropivacaine, articaine, and etidocaine.

Combinations include lidocaine/prilocaine (EMLA) and lidocaine/tetracaine (Rapydan), lidocaine/epinephrine/tetracaine (LET), and tetracaine/adrenaline/cocaine (TAC).

Topical anesthetics include benzocaine, lidocaine, cocaine, proparacaine, and oxybuprocaine.

Bupivacaine: Useful because of long duration, commonly used in spinals, high-quality sensory block relative to motor block

Chloroprocaine: Most rapid hydrolysis among ester class, useful in obstetrics owing to rapid onset and low risk of systemic toxicity or fetal exposure

Cocaine: Vasoconstrictor properties, central nervous system stimulation (hypertension, tachycardia, coronary ischemia)

Lidocaine: Very versatile anesthetic that is used for topical, regional, neuraxial, and intravenous anesthesia

Ropivacaine: Greatest margin of safety among long-acting local anesthetics

Tetracaine: Useful in spinal anesthesia because of rapid onset, long duration, less sensory blockade than bupivacaine

Topical Formulations

Benzocaine: 20% solution for mucosal anesthesia; risk of methemoglobinemia, especially with repeated doses

Cocaine: 4% solution for topical anesthesia (sinus surgery, awake intubation) or 11.8% TAC for wound repair

EMLA: 2.5% lidocaine and 2.5% prilocaine eutectic mixture for minor procedures (pediatric IV placement); onset, 45-60 minutes; duration, 2 hours; typical adult dose, 2.5-10 g

Table 1. EMLA Maximum Pediatric Dosing (Open Table in a new window)

Age	Weight	Maximum Dose
0-3 months	< 5 kg	1 g
3-12 months	>5 kg	2 g
1-6 years	>10 kg	10 g
7-12 years	>20 kg	20 g

J-Tip: 1% buffered lidocaine for minor procedures (pediatric IV placement), needle-free pressure-injection device

LET: 4% lidocaine plus 0.1% epinephrine and 0.5% tetracaine for minor procedures (laceration repair), as aqueous solution or methylcellulose gel

LMX: 4% liposomal solution for minor procedures (pediatric IV placement); onset, 30 minutes, maximum 100 cm² application area in children < 10 kg

Table 2. Onset, Maximum Dose, and Duration of Local Anesthetics (Open Table in a new window)

Drug	Onset	Maximum Dose (With Epinephrine)	Duration (With Epinephrine)	Max Infiltration Dose
Lidocaine	Rapid	4.5 mg/kg (7 mg/kg)	120 min (240 min)	300 mg
Mepivacaine	Rapid	5 mg/kg (7 mg/kg)	180 min (360 min)	300 mg
Bupivacaine	Slow	2.5 mg/kg (3 mg/kg)	4 hours (8 h)	150 mg
Ropivacaine	Medium	2-3 mg/kg	3 hours (6 h)	200 mg
Levobupivacaine	Medium	2 mg/kg or 400 mg in 24 hours	4-6 hours (8-12 h)	150 mg
Procaine	Slow	8 mg/kg (10 mg/kg)	45 min (90 min)	500 mg
Chloroprocaine	Rapid	10 mg/kg (15 mg/kg)	30 min (90 min)	600 mg
Etidocaine	Rapid	2.5 mg/kg (4 mg/kg)	4 hours (8 h)
Prilocaine	Medium	5 mg/kg (7.5 mg/kg)	90 min (360 min)	400 mg
Tetracaine	Slow	1.5 mg/kg (2.5 mg/kg)	3 hours (10 h)
Calculate the maximum tolerable dose by considering the dose to be used; patient weight; and renal, cardiac, or hepatic disease. Note: Although these are typically quoted maximum doses, many are not evidence-based,^[1] and some situations warrant lower doses, including late-stage pregnancy.

Table 3. Pharmacokinetics of Common Local Anesthetics^[5] (Open Table in a new window)

Local	pKa	Nonionized	Potency	Topical	Local	Intravenous	Peripheral	Epidural	Spinal
Procaine	8.9	3% at pH 7.4	1	No	Yes	No	Yes	No	Yes*
Chloroprocaine	8.7	5% at pH 7.4	2	No	Yes	Yes	Yes	Yes	Yes*
Tetracaine	8.5	7% at pH 7.4	8	No	No	No	Yes	No	Yes
Lidocaine	7.9	24% at pH 7.4	2	Yes	Yes	Yes	Yes	Yes	Yes*
Mepivacaine	7.6	39% at pH 7.4	2	No	Yes	No	Yes	Yes	Yes*
Prilocaine	7.9	24% at pH 7.4	2	Yes	Yes	Yes	Yes	Yes	Yes*
Bupivacaine	8.1	17% at pH 7.4	8	No	Yes	No	Yes	Yes	Yes
Levobupivacaine	8.1	17% at pH 7.4	8	No	Yes	No	Yes	Yes	Yes
Ropivacaine	8.1	17% at pH 7.4	6	No	Yes	No	Yes	Yes	Yes
*There is controversy regarding the use of these agents in spinal anesthesia, and some are known to increase the risk of transient neurologic symptoms (TNS). Lidocaine spinal dosage should not exceed 60 mg, epinephrine should not be used, and the concentration should be 2% or less.^[6]

Spinal Dosing

Bupivacaine is the agent of choice for most spinal anesthetics, with standard hyperbaric formulation 0.75% bupivacaine in 8.25% dextrose. For perineum or lower limb surgery, a dose of 4-10 mg is used. For lower abdominal surgery (eg, cesarean section), 12-14 mg is used, and, for upper abdominal surgery, 12-18 mg.

If saddle anesthesia is the goal, the patient should remain in the sitting position for 3-5 minutes after subarachnoid injection. Otherwise, the patient should be moved to the supine position immediately after subarachnoid injection.

Bupivacaine plain 0.5% "heavy" is an isobaric formulation with the potential for a longer duration of action. Onset is typically 5-8 minutes with an approximate duration of effect lasting 2-3 hours. The duration for abdominal surgery, which includes cesarean section, is approximately 45-60 minutes.

Table 4. Spinal Heavy 0.5% Bupivacaine Dosing^[7] (Open Table in a new window)

Indication	Dose	Dose	Duration
Urological surgery	1.5-3 mL	7.5-15 mg	2-3 hours
Lower limb, hip surgery	2-4 mL	10-20 mg	2-3 hours
Abdominal surgery	2-4 mL	10-20 mg	45-60 min

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Table 1. EMLA Maximum Pediatric Dosing

Age	Weight	Maximum Dose
0-3 months	< 5 kg	1 g
3-12 months	>5 kg	2 g
1-6 years	>10 kg	10 g
7-12 years	>20 kg	20 g

Table 2. Onset, Maximum Dose, and Duration of Local Anesthetics

Drug	Onset	Maximum Dose (With Epinephrine)	Duration (With Epinephrine)	Max Infiltration Dose
Lidocaine	Rapid	4.5 mg/kg (7 mg/kg)	120 min (240 min)	300 mg
Mepivacaine	Rapid	5 mg/kg (7 mg/kg)	180 min (360 min)	300 mg
Bupivacaine	Slow	2.5 mg/kg (3 mg/kg)	4 hours (8 h)	150 mg
Ropivacaine	Medium	2-3 mg/kg	3 hours (6 h)	200 mg
Levobupivacaine	Medium	2 mg/kg or 400 mg in 24 hours	4-6 hours (8-12 h)	150 mg
Procaine	Slow	8 mg/kg (10 mg/kg)	45 min (90 min)	500 mg
Chloroprocaine	Rapid	10 mg/kg (15 mg/kg)	30 min (90 min)	600 mg
Etidocaine	Rapid	2.5 mg/kg (4 mg/kg)	4 hours (8 h)
Prilocaine	Medium	5 mg/kg (7.5 mg/kg)	90 min (360 min)	400 mg
Tetracaine	Slow	1.5 mg/kg (2.5 mg/kg)	3 hours (10 h)
Calculate the maximum tolerable dose by considering the dose to be used; patient weight; and renal, cardiac, or hepatic disease. Note: Although these are typically quoted maximum doses, many are not evidence-based,^[1] and some situations warrant lower doses, including late-stage pregnancy.

Table 3. Pharmacokinetics of Common Local Anesthetics ^[5]

Local	pKa	Nonionized	Potency	Topical	Local	Intravenous	Peripheral	Epidural	Spinal
Procaine	8.9	3% at pH 7.4	1	No	Yes	No	Yes	No	Yes*
Chloroprocaine	8.7	5% at pH 7.4	2	No	Yes	Yes	Yes	Yes	Yes*
Tetracaine	8.5	7% at pH 7.4	8	No	No	No	Yes	No	Yes
Lidocaine	7.9	24% at pH 7.4	2	Yes	Yes	Yes	Yes	Yes	Yes*
Mepivacaine	7.6	39% at pH 7.4	2	No	Yes	No	Yes	Yes	Yes*
Prilocaine	7.9	24% at pH 7.4	2	Yes	Yes	Yes	Yes	Yes	Yes*
Bupivacaine	8.1	17% at pH 7.4	8	No	Yes	No	Yes	Yes	Yes
Levobupivacaine	8.1	17% at pH 7.4	8	No	Yes	No	Yes	Yes	Yes
Ropivacaine	8.1	17% at pH 7.4	6	No	Yes	No	Yes	Yes	Yes
*There is controversy regarding the use of these agents in spinal anesthesia, and some are known to increase the risk of transient neurologic symptoms (TNS). Lidocaine spinal dosage should not exceed 60 mg, epinephrine should not be used, and the concentration should be 2% or less.^[6]

Table 4. Spinal Heavy 0.5% Bupivacaine Dosing ^[7]

Indication	Dose	Dose	Duration
Urological surgery	1.5-3 mL	7.5-15 mg	2-3 hours
Lower limb, hip surgery	2-4 mL	10-20 mg	2-3 hours
Abdominal surgery	2-4 mL	10-20 mg	45-60 min