What's New in Local Anesthesia
STANLEY F. MALAMED, DDS, PROVIDES A BRIEF
UPDATE ON IMPORTANT CONSIDERATIONS WHEN
USING LOCAL ANESTHESIA.
Stanley F. Malamed, DDS, is dentistry's
best-known expert on local anesthesia
and his book, Handbook of Local
Anesthesia, has been the go-to guide
for safe anesthesia practice in dentistry since the
first edition was published in 1978. In 2012, the
sixth edition of the handbook was released, revealing
some changes on maximum recommended
dosages (MRDs). In this interview with
Dimensions of Dental Hygiene, Malamed discusses
these differences, in addition to changes in anesthetic
labeling and considerations for specific patient
The sixth edition of your book includes only the United States Food
and Drug Administration (FDA) MRDs, as opposed to previous
editions that also featured your own MRDs. Why did this change?
The MRDs for currently available local anesthetics listed in the 5th
edition of the Handbook of Local Anesthesia had two columns: FDA recommended
MRDs and then my own MRDs.1 In some cases, the values
in both columns were the same, but in others there were differences.
Usually, mine reflected slightly lower values. They were obtained from
other authoritative sources and I felt they were quite reasonable, thus
their inclusion. However, readers (especially teachers of local anesthesia
in dental and dental hygiene programs) mentioned that having two sets
of MRDs was confusing to both them and their students. Because the
FDA sets the MRD standards, I decided that future editions (sixth and
onward) would only present the FDA values.2 The only goal here was to
try to avoid confusion. Interestingly, the American Academy of Pediatric
Dentistry still lists the lower values in its monograph.3
Manufacturers' drug data sheets now list the volume per cartridge
as 1.7 mL. Should drug dose calculations reflect this
volume or the traditional 1.8 mL volume that has been the basis for
calculations for many years?
There has not been any change in the dental local anesthetic cartridge.
The adjustment has been only in labeling. This initially occurred
with the introduction of articaine in 2000. During discussions
between the drug's manufacturer and the FDA, the question of "truth
in advertising" arose. The FDA asked the manufacturer if it could guarantee
that every local anesthesia cartridge contained at least 1.8 mL of
solution. Because cartridges are filled by machine, the answer was no.
The manufacturer could, however, guarantee that every local anesthesia
cartridge contained at least 1.7 mL. Robertson et al published a paper in
2007 that assayed 50 lidocaine hydrochloride and 50 articaine hydrochloride
cartridges, and found an average volume of 1.76 +/- 0.023 mL in
each.4 My recommendation is to continue to use 1.8 mL as the cartridge
volume when determining MRDs for patients.
Some sources suggest that prilocaine is contraindicated in pregnant
patients due to its association with methemoglobinemia, and concerns
regarding oxygenation and the fetus. What is your opinion?
Prilocaine's MRD is based on the drug's ability to increase the levels
of methemoglobin (a type of hemoglobin) as it undergoes metabolism
in the body. This is only a concern among patients with a history
of congenital methemoglobinemia (a condition where methemoglobin
levels are higher than normal). Administering large prilocaine doses to
such individuals can push them into the danger zone, which would result
in respiratory distress and cyanosis of mucous membranes. Interestingly,
the administration of oxygen to this patient would not prove very successful
because his or her hemoglobin is not able to carry oxygen. As for
pregnancy, prilocaine is not contraindicated, but its dosage should be
kept minimal (as dosages should be with all local anesthetics in all clinical
situations, not only during pregnancy).
Should topical anesthetics that contain prilocaine or benzocaine
be avoided during pregnancy?
Prilocaine and benzocaine (a more commonly used topical anesthetic)
can elevate methemoglobin levels in the blood. Large
doses of either drug should be avoided during pregnancy. The use of
other local anesthetics that do not produce elevations in methemoglobin
levels is preferred.
What should dental hygienists consider when selecting between
4% articaine with 1:200,000 epinephrine or 4% articaine with
Both of these formulations provide pulpal anesthesia of approximately
1-hour duration and soft tissue anesthesia up to about
5 hours, and these values are for patients exhibiting normal response
(ie, in the middle of the bell curve). Selection is entirely up to the clinician
administering the drug. Both formulations are effective and safe.
The use of vasoconstrictors should be restricted in patients who
have taken methamphetamines or cocaine within 24 hours.
Does the use of marijuana or any local anesthetic agents impact the
selection, and, if so, for how long?
The reason for withholding vasoconstrictors from patients having
taken methamphetamines or cocaine within 24 hours is fairly obvious—
excessive stimulation of the cardiovascular system increases the risk
of cardiac dysrhythmias, potentially leading to cardiac arrest. I do not
believe this is a problem with marijuana use because it's not a stimulant;
rather it is a central nervous system depressant. To my knowledge, there
are no cardiovascular stimulatory actions associated with cannabis.
Malamed S. Handbook of Local Anesthesia. 5th ed. St Louis: Mosby; 2004.
Malamed S. Handbook of Local Anesthesia. 6th ed. St Louis: Mosby; 2013.
American Academy of Pediatric Dentistry. Guideline on Use of Local
Anesthesia for Pediatric Dental Patients. Available at: www.aapd.org/
media/Policies_Guidelines/G_LocalAnesthesia.pdf. Accessed May 6, 2013.
Robertson D, Nusstein J, Reader A, Beck M, McCartney M. The
anesthetic efficacy of articaine in buccal infiltration of mandibular
posterior teeth. J Am Dent Assoc. 2007;138:1104–1112.
From Dimensions of Dental Hygiene. July 2013; 11(7): 21–22.