Possible Side Effects of Local Anesthesia

Dental News

Small procedures on the body, like a skin biopsy, are great candidates for local anesthesia. An injection or topical cream may be used. If you’ve ever had an injection by a dentist, you’ve had a local anesthetic. Fast-acting, virtually pain-free and convenient, local anesthetics enable much of medicine to occur. Patients can remain awake and leave following their procedure. After anesthesia side effects are also exceedingly rare. But since no procedure is without risk, let’s understand each. 

What is Local Anesthesia?

Local is a route of administration of a drug. It means that a drug, in this case anesthesia, is given near the site of action for the lowest risk of side effects. The entire body does not need to be shut down (general anesthesia) in order for one area to be worked on without pain, in many cases. Recovery time for ‘going under’ is longer than local anesthesia and risks not only a wider range of side effects, but side effects of a very serious nature, such as cardiac arrest. 

Types of Local Anesthetic

There are a lot of drugs that block signals to the brain sent by nerve pathways, but lidocaine is the most well-known. Cocaine was the original anesthetic and it developed the foundation for the ‘caine’ family of anesthetics. Different anesthetics are used for different reasons by anesthetists. For example, longer procedures require longer effectiveness times, and for that bupivacaine is often a good choice. 


Numbing medications are commonly applied topically. Drugs like lidocaine don’t necessarily need to be injected during simple procedures like skin biopsies. Examples you might recognize include proxymetacaine, tetracaine, oxybuprocaine, butamben, dibucaine and of course lidocaine. These topicals can also simply relieve pain without needing to prepare for a procedure, such as in the case of insect bites, minor burns, cuts, scratches, and exposure to sources of irritants like poison sumac, poison oak and poison ivy. 

  • Duration: Topical painkillers only last about 30 minutes on average. 


Your doctor may start with a topical like a lidocaine cream to numb the area, then use an injectable to provide more numbness for your procedure. Local anesthetics vasodilate and are absorbed by the blood stream; because of this, vasoconstrictors like norepinephrine, levonordefrin and epinephrine are added to balance out blood pressure. Anesthetics want to leave an area of the body because of their vasodilative nature, but the vasoconstrictors keep them in the area where they are needed for longer action. 

  • Onset time: How quickly a local anesthetic takes effect depends on how acidic it is; more acidity, longer onset time. 

Regional & General Anesthetics

Local, regional and general anesthetics are terms anyone could mix up. While we know that local means pain relief via topical or injected anesthetic at the site of action, what do regional and general mean? 

  • Local: This means that you only numb a small area of tissue in the location of the procedure. For some patients local anesthetics pose less side-effects or other health risks, highlighting the fact that anesthetics can be used strategically based on the particulars of each patient. 
  • Regional: Regional numbs a larger area than local, but it is still confined to the area of the procedure and does not make the patient unconscious. Included in this type of anesthetic are epidurals and spinal blocks. In some cases patients need to be sedated or calmed through the administration of other drugs. 
  • General: Administered via intravenous injection or inhalation, general anesthetics do make a patient unconscious. The unique details of each patient determine the use of this procedure. For example, children can be given general anesthesia simply because they won’t sit still for a procedure, not because they need to necessarily be unconscious. Most of the major side effects mentioned in any literature or online article will refer to general anesthesia. The more sedative, the more risk, but it’s less risky than not treating the condition in question. 
  • Conscious sedation: This is essentially a gray area of sedation between regional and general anesthetics. It’s total lack of sensation without losing consciousness, in an effort to curb anxiety and stronger side effects and risks of general anesthesia. However, as with any sedation, you also risk lingering effects of sedation, including feeling sleepy, nausea and headaches. 

Possible Side Effects

Usually, the only oral surgery anesthesia side effects are a tingling that wears off soon after your procedure. However, some side effects, like local anesthetic toxicity, are possible through being administered high doses of anesthetics. Aesthetics can’t, by their nature, produce irreversible neurological damage because they block nerve conduction temporarily.

There are many types and varieties of side effects including wisdom teeth anesthesia side effects and impacts on certain age groups like anesthesia side effects in elderly patients. In fact, this older group has some unique risk factors, being more prone to aspiration, pressure ulcers, and adverse drug reactions.

Here are some of the side effects experienced in most average adults:

  • Dry mouth: This is common after receiving anesthetics. You may also be nauseated, so make sure to sip water slowly, instead of drinking quickly. 
  • Allergic reactions: Urticaria and anaphylaxis in rare cases, also referred to as ‘immediately hypersensitive’ due a fast, strong reaction to the local anesthetic. Contact dermatitis is an unlikely but possible side-effect, peaking usually within three days.
  • Welts: Large hive-like skin irritations on the body or in the throat. 
  • Fatigue: Lack of energy without any motivation—this is fatigue, as opposed to drowsiness or sleepiness or tiredness. Most fatigue fades with a good diet and adequate rest. 
  • Infection: Needles come with risks, such as contamination and transmission of disease like hepatitis. However, per the CDC, infection is preventable using proper safe injection practices. Most of the time an infection related to aesthetics is at the injection site. 
  • Broken needle: Although rare, needles can break off while still inside the skin of a patient. If not addressed quickly, this is a clear infection risk. Weakness at the hub of the needle is the common culprit. 
  • Hypothermia: When your body temperature drops below 95°F, hypothermia occurs. Symptoms include confusion, stumbling, slowed speech, clumsiness, slowed breathing and excessive shivering. There are a few reasons why anesthesia causes hypothermia: heat moves from the core to the extremities during vasodilation, metabolism drops by almost a third, operating rooms are cold, room-temp fluids are administered and operating wounds cause evaporation. With local anesthetics hypothermia is an extremely rare side effect, but shivering and trembling can occur when large doses of anesthetics are administered. 
  • Cardiac arrest: Anesthesia-related cardiac arrest do happen, both directly and as a contribution of the effects of this class of drugs. An independent study commissioned to give numbers of cardiac arrest from anesthesia found 37 of 160 studied cardiac arrests were related to post anesthesia side effects. 
  • Nerve injury: This is a common occurrence that anesthesiologists often fight against, and a major contributor to malpractice claims. The spinal cord, nerve root, lumbosacral nerve root, brachial plexus and ulnar nerve are common sites of injury. Regional anesthetics are more likely to cause issues with the spine and lumbosacral nerve root. Nerve root injury usually causes a lot of pain, most often resulting from subtly shifting vertebrae, which can only occur in the cervical and lumbar spinal regions. 
  • Headaches: Headaches happen commonly after anesthesia, but usually only when you’re made unconscious. 
  • Back pain: You may have pain at the injection site, or some tenderness, but it will fade within 1-3 days. 
  • Difficulty breathing: During sedation heart rate can slow, and breathing can become difficult, though this is rare and easily treated with oxygen by your nurse. 
  • Nausea or vomiting: Nausea is a common symptom of general and regional sedation, but not of local anesthetics. 
  • Hypotension: Otherwise known as low blood pressure, this commonly occurs during anesthesia when blood pressure drops below 80-90/40. Administering a vasoconstrictor or positive inotrope, which helps strengthen heart contractions, can alleviate these blood pressure issues. 
  • Itching: With local anesthetics, itching at the site of injection can happen. 

How Health & Age Effect Anesthesia

It’s impossible to talk about the side effects of too much anesthesia without addressing how specific they are to a patient’s age, health and comorbidity issues. Local anesthetics pose few risks, but other forms of anesthetics 

  • Heart, lung, kidney or liver problems: These health problems often slow the time it takes for a drug to leave the body, meaning dosage may need to be adjusted accordingly. Also, in pregnant women, medical conditions that pose risk to the baby result in an increased risk of side effects from local anesthetics, despite being at standard dosages. 
  • Certain neurological conditions: General anesthesia risks increase if a person has mental illness, thyroid disease, Parkinson’s disease, Alzheimer’s disease or a history of stroke. 
  • Pregnancy: Many women forgo treatments that require anesthetics while pregnant. For example, dentists rarely treat pregnant women, and they are the biggest users of local anesthetics. Why? Because drugs transfer to the fetus, at least theoretically when administered materially. However, lidocaine has been proven to have almost zero negative effect on the mother or fetus. 
  • Timing: When an anesthetic is administered can also have a big impact on efficacy, such as during pregnancy. The first trimester poses the highest risk to the fetus, so patients are advised to not receive treatment such as dental procedures during this time. 
  • Special needs: These children and adults may have additional complications caused by medical conditions. 
  • Age: Older patients can experience memory problems, confusion or delirium following surgery. It’s important to monitor them closely and adjust their dosages accordingly. 


Methemoglobinemia has been linked to local anesthetics. In this condition too little oxygen is delivered to the cells of the body, leading to standard respiratory complications: blue-colored skin, poor muscle coordination, nausea, shortness of breath, dizziness and headache. When the 600mg maximal safe dose is exceeded, the anesthetic prilocaine can become toxic in adults and newborns 3 months and younger, even with EMLA cream, which contains lidocaine and prilocaine. It’s important to note that doctors will test you for this disorder and others before any procedure. 

Potential Risks

  • Abuse Potential: Local anaesthetics have a risk for abuse potential that is not widely known. However, to anyone who’s had a sinus headache, ocular pain is well known. Eye pain is usually very intense, caused by neuropathic pain resulting from nerve irritation. Because of this, patients seek out topical anesthetics, becoming dependent on them and try to get prescriptions to kill the pain of fabricated conditions. The problem with using topicals this way—and why they of course aren’t prescribed for ocular use—is that damage to corneal tissues is often irreversible and severe with repeated application. What these patients don’t realize is that their doctors could treat their pain likely in its entirety with the use of anticonvulsants. It should be noted that synthetic anesthetics were developed to curb abuse. Cocaine is still heavily abused today, and it was the original anesthetic.
  • Improper Training: A lot of discomfort around injections is caused by a medical professional who can not find the proper injection site. Patients are prodded several times, causing pain, until the injection site is found. Medical professionals may also simply inject anesthetics into the wrong area of the body, such as a vein instead of tissue. Unfortunately, avoidable mistakes are a reality of any medical procedure, including anesthetic formulations that are simply incorrect for a particular patient. Furthermore, if a local anesthetic is injected into a site of infection, the drug will not work or will be reduced in efficacy. Improper training leads to increased risk of every type when a medical procedure is performed. 
  • Local Anesthetic System Toxicity (LAST): Local anesthetics are becoming more popular, increasing the incidence of toxicity. Though extremely rare, certain health issues and age make some patients more likely to have this sort of complication. Symptoms of over-absorption of medicine include weakness, paleness, trouble breathing, shivering, buzzing in the ears, hot/cold/numb feelings, confusion, blurred or double vision, and dizziness. Too much anesthetic can even cause seizures. 

Anesthesia is a Custom Procedure

There is no way to judge anesthesia before getting a procedure, due to so many variables. Each patient, each attending physician, has different needs and makes different decisions. When a team of doctors carefully creates an anesthetic tailored to the patient and the procedure, side effects are limited and rare. Your doctor will always explain to you any and all side effects that could occur. 

Safer Administration of Anesthesia

STA Single Tooth Anesthesia is revolutionizing the administration of local anesthesia to patients. This computer assisted technology allows for greater precision and less discomfort, helping dentists grow their businesses faster.