Why Does Local Anesthesia Not Work On Me?

Local anesthesia is commonly used in dental procedures and minor surgeries to numb small areas, like the gums, and prevent pain. These drugs, such as lidocaine, temporarily block pain signals by binding to sodium channels in nerves.

Local anesthesia is usually effective for most people. However, there are cases where it does not work as expected.

Reasons Local Anesthesia May Not Work.

Problems with administration are a common and usually temporary reason local anesthesia does not work. The anesthetic might not be injected in the right spot or the dose may be too low. Differences in patient anatomy, such as the position of nerves, often contribute to administration challenges.

While administration issues may affect anyone, some patients also have genetic or health conditions that make them specifically resistant to local anesthetics. This means a standard dose does not provide enough pain relief.

Patient Factors.

Chronic factors like genetics often cause more resistance to local anesthetics than temporary conditions, but responses vary widely between patients.

Genetic Traits and Conditions.

Genetic differences can affect how the body processes local anesthetics in various ways. These factors include:

• Sodium Channel Mutations: Genetic changes in these nerve structures can make them less responsive to anesthetics.
• Increased Enzyme Activity: Some people’s bodies break down anesthetics too quickly, so it doesn’t last long enough to work.
• Red Hair and MC1R Gene Mutation: Patients with red hair may need more anesthesia. This is linked to a change in the MC1R gene, which may make them less sensitive to anesthesia.
• Ehlers-Danlos Syndrome (EDS): This connective tissue disorder can affect how local anesthetics are absorbed and spread through the body. Differences in nerve structure can also reduce these drugs’ effectiveness.

Other Medical Conditions.

Medical conditions can alter nerve function or interfere with how local anesthetics interact with nerves.

• Chronic Pain Conditions: Disorders like fibromyalgia and complex regional pain syndrome (CRPS) can change how the nervous system processes pain. These conditions may cause heightened pain sensitivity (called central sensitization), making local anesthesia less effective.

• Inflammation or Infection: Inflamed or infected tissues are more acidic. This makes it harder for local anesthetics to block nerve signals.

Variations in Anatomy.

Everyone’s bodies are slightly different. Extra nerves and unusual nerve paths can make it harder to administer anesthetics to the right spot. Some patients may have more blood flow in the targeted area, which can remove the anesthetic faster and reduce its duration.

Chronic Drug Use.

Long-term use of substances such as opioids and alcohol may lead to tolerance or altered nerve sensitivity.

Anxiety or Stress.

Stress and anxiety can increase pain sensitivity. Stress hormones, like cortisol, can make nerves more active, reducing how well anesthesia works.

What Can Providers Do?

In many cases effective pain relief can be achieved by adjusting the dose or injection site. A provider may also:

• Switch to a different anesthetic.
• Use nerve blocks or ultrasound guidance.
• Add buffers or adjunct drugs to improve efficacy.
• Treat infection and inflammation beforehand
• Explore alternative anesthesia options, such as sedation or general anesthesia.

What Should Patients Tell Their Provider?

If local anesthesia hasn’t worked before, patients should tell their healthcare provider before the procedure. Important details include any previous issues, the drugs used, and whether they feel nervous during treatments. This helps the provider adjust the plan to the patient’s needs and provide better pain relief.

By talking openly with their provider and exploring alternative strategies, most patients can achieve effective and comfortable pain relief with local anesthesia.