Novocaine Allergy Part I – The Esters

This will be the first of a three part series covering the various types of allergies associated with dental local anesthetics. Why write this? Well, some of the most frequently used search terms that cause people to arrive at this site are some combination of “allergy” and “novocaine.”

Needle used for novocaine injection at the dentist

People love to Google what they hate. And people hate the “novocaine” shot!

Over the years, I’ve observed that many of my own patients as well as readers and commenters on this blog think they may be allergic to the local anesthetic used at the dentist. This is not surprising given that over 1 million local anesthetic injections are administered each year in dental offices in the United States. With this level of frequency, adverse events are bound to happen, some of which may be interpreted as allergies.

The three parts are:

  1. The Esters
  2. Methylparaben and Sulfites
  3. True amide allergies

The titles of the three parts may appear cryptic, weird, or just plain boring. But this is how it needs to be organized. We’ll start with a brief history of local anesthetics.

Cocaine and Procaine

Coca leaves to make cocaine - a local anesthetic

If you crush these up you get dentistry’s first local anesthetic!

As I wrote about previously in the post Cocaine and Dentistry, cocaine was the first local anesthetic used in dentistry. Cocaine was first used in a dental procedure as an injectable local anesthetic in 1884. While it was a very effective anesthetic, there were unwanted side effects (euphoria, cardiovascular stimulation, addiction, etc.).

In 1905, another anesthetic was synthesized called procaine. It had all the anesthetic properties of cocaine but none of the undesirable side effects. Because of this, it was very quickly adopted, and a brand name version of procaine – novocaine – was launched.

What the Heck is an Ester?

Ester functional group seen in cocaine and novocaine

Chemical symbol of an ester (courtesy wikipedia)

An ester is a term from organic chemistry that describes a specific part of a molecule. I will not describe that portion in detail because it is so boring it will make 99.9% of you hit the back button on your browser!

The diagram here is not that important. What is important is that cocaine, procaine (brand name novocaine), and many other dental local anesthetics are considered “ester type anesthetics.” They are given this name for two reasons. First, there’s the obvious reason: they all contain an ester group. The second reason is to differentiate them from another family of local anesthetics called “amide type anesthetics.”

Allergies to Ester Based Anesthetics

Now we actually get to what everyone wants to know. And that is to begin talking about allergic reactions to dental local anesthetics. We begin with ester based local anesthetics because at one point these were the only local anesthetics available. I’ve organized the points in bullet format for easy reading:

  • When ester based local anesthetics are injected into the body, they are metabolized into a chemical called para-aminobenzoic acid (also called PABA).
  • PABA is known to cause allergic reactions in some people. So, back when novocaine was actually being commonly used (from 1905 to the mid 1950s), patients frequently experienced true novocaine allergies.
  • Because of the documented allergic reactions to PABA (caused by injections of ester based local anesthetics), ester based injectable dental local anesthetics are no longer used in the United States.
  • What is used instead? You guessed it – amide type anesthetics.
  • Ester based local anesthetics are only used in dentistry in the U.S. as topical anesthetics (also known as numbing jelly). The most common one is benzocaine.
topical benzocaine - an ester local anesthetic still used

Topical Benzocaine is still used in the U.S. routinely.

Other ester based local anesthetics besides procaine and benzocaine include tetracaine, chloroprocaine, propoxycaine, and cocaine. But note these are no longer used in dentistry in the United States.

So, to summarize, true novocaine allergies exist, but they do not occur anymore because novocaine is no longer used.

But what about allergies from other sources? What does a true allergy look like clinically? When my heart races at the dentist does that mean I’m having an allergic reaction?

These and other subjects will be covered in Parts 2 and 3…

Cocaine and Dentistry

Most people are unaware that cocaine was used in dentistry as a local anesthetic. During the height of its use, cocaine was considered remarkably effective for both dental procedures and curing toothaches.  Cocaine was a critical part of the history of local anesthetics in dentistry!

Cocaine and Dentistry in the 1800s

Print ad for Cocaine tooth drops used for teething pain

Print ad for Cocaine Tooth Drops for teething pain in children, circa 1885.

In 1860, a young German chemist named Albert Niemann isolated cocaine from the leaves of the South American coca bush.  He called the new compound “Cocain.” After his discovery, chemists in Europe and the U.S. began to experiment with it.  Sigmund Freud was an early proponent of its medicinal uses and encouraged a physician colleague Dr. Karl Koller to experiment with its analgesic properties.

Koller experimented with cocaine and then demonstrated the local anesthetics effects at an Ophthalmic meeting in 1884.  News spread quickly to the United States and only a couple of weeks of Koller’s demonstration, it was used in dentistry. William Haldsted MD injected cocaine into the lower jaw of a patient and then extracted a tooth with no pain or sensation felt by the patient. Thus marked the beginning of the use of local anesthetics in dentistry.

Drawbacks of Dental Use of Cocaine

News of this spread quickly and soon cocaine was widely adopted as an anesthetic by dentists and physicians starting in the late 1880s. It is important to remember that prior to the introduction of cocaine, dental procedures were done without any numbing at all!

Key properties of cocaine included:

  • Quick onset and short duration of action.
  • Localized effects.
  • Feelings of euphoria in the individual receiving the cocaine.
  • Certain cardiovascular effects such as increased heart rate.
Coca leaves used to make cocaine which was the first local anesthetic used in dentistry

Coca leaves used to make cocaine

The feelings of euphoria were not lost on those dentists and physicians administering the cocaine.  Soon, many dentists and physicians developed a dependency upon it, including Halsted himself. In fact, three of his colleagues actually died without recovery from the addiction of cocaine. Once this was observed on a large scale, chemists quickly sought to develop an alternative to cocaine for use as local anesthetic.

Next Step: Novocaine

In 1905, a new local anesthetic, Procaine, was introduced. Procaine had all the desired effects of cocaine as a local anesthetic, but did not posses the addictive potential nor the other negative side effects. Procaine then quickly replaced cocaine as the local anesthetic of choice in dentistry.  One company then made the fateful decision to market procaine under a new brand name: Novocain. From that point on, the name Novocaine has become synonymous with “the shot you get at the dentist”, a phenomenon I documented in this Dental MythBuster post.

Carpule of lidocaine and epinephrine the most popular dental local anesthetic used in dentistry for numbing

Lidocaine with epinephrine

Novocaine had its own drawbacks so a new generation of local anesthetics were then developed many years later. Today, lidocaine (pictured on the left) is the most popular local anesthetic used in dentistry in the United States. I routinely use lidocaine and another local anesthetic, articaine (brand name septocaine), on a daily basis in my practice in Orange, CT. Both are extremely effective and it is rare that I observe any complications.

Interestingly, redheads have a well documented resistance to dental local anesthetics, research I documented in one blog post about redheads and then another recent article.  I always explain to red haired patients the research on this subject and they are fascinated to learn about it.  It is likely that red haired individuals would have a resistance to the anesthetic properties of cocaine as well.

But all patients – regardless of hair color – are glad that they do not have to be injected with cocaine in order to have dental procedures done!