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Analgesia vs. Anesthesia: Overview, Differences & Types

Caitlin Daley, Artem Cheprasov
  • Author
    Caitlin Daley

    Caitlin Daley is a 7th grade science teacher from Powdersville, SC. She earned her bachelors of arts degree from Georgia Southern University in Statesboro, Georgia. Mrs. Daley is certified in elementary education, middle level science, and middle level social studies. Besides having her initial teaching certificate, she has also added GT endorsement, and is considered a PLTW teacher. Mrs. Daley has been teaching for 20 years, with over 15 years in middle school science.

  • Instructor
    Artem Cheprasov

    Artem has a doctor of veterinary medicine degree.

Learn about analgesia and anesthesia. Understand the difference between analgesia and anesthesia, learn their mechanisms of action, and see common examples. Updated: 05/31/2022

Analgesia vs. Anesthesia

Analgesia Overview

Analgesia refers to when a person's pain is relieved or reduced due to analgesics. Commonly known as painkillers or pain relievers, analgesics do not alter a person's consciousness or fully block the nerves; instead, they impact the messages sent to the brain about the pain. Analgesia relieves different types of pain that can include headaches, muscle pain, and pain from basic injuries. Many analgesics can be purchased over the counter, but some stronger ones require a prescription.

Examples and Uses of Analgesics

There are many different types of analgesics that can help relieve pain. These medications can be classified into two categories. The first category includes over-the-counter or OTC medications. The second category includes opioids or narcotics.

OTC are medications that can be purchased in most grocery stores and pharmacies. They do not require a doctor's prescription. There are two groups of OTC medications. The first group is acetaminophen, and the second group is non-steroidal anti-inflammatory drugs or NSAIDs. Common examples include:

  • Acetaminophen (Tylenol)
  • Aspirin
  • Naproxen (Aleve)
  • Ibuprofen (Advil, Motrin)

Analgesics are important because they help mitigate pain and can be easily obtained. OTC medications are often taken orally and used to treat pain for common conditions such as:

  • Sore muscles
  • Menstrual cramps
  • Headache
  • Arthritis
  • Toothache
  • Basic injuries

If the pain is not controlled by OTC medication, then opioids or narcotics can be prescribed. These are very powerful drugs that relieve pain but can come with risks that include addiction. If opioids or narcotics are prescribed, then the patient will also be under a doctor's supervision. Some common opioids/narcotics, which have various routes of administration, include:

  • Morphine (MS Contin, Avinza, Kadian)
  • Oxycodone (Oxycontin)
  • Methadone (Dolophine)
  • Hydromorphone (Dilaudid)
  • Codeine (Panadeine, Nurofen Plus, Mersyndol)
  • Meperidine (Demerol)
  • Fentanyl (Duragesic)

Anesthesia Overview

Anesthesia refers to when a person is either numbed or put in a sleep-like, unconscious state before medical procedures or surgery. With anesthesia, a person does not feel pain or any physical sensations at all. Anesthesia involves anesthetic medications that are commonly in the form of intravenous (IV) drugs or inhaled gases. These medications block the nerve receptors, which in turn cause the brain to not respond to pain signals or reflexes. Anesthesia is normally recommended for procedures or surgeries that:

  • Take a long time
  • Result in significant blood loss
  • Expose the patient to a cold environment
  • Affect breathing, especially in the chest or upper abdominal region

Examples and Uses of Anesthetics

There are two types of anesthesia: local and general. With local anesthesia, medications known as numbing agents block the impulses in nerves that relay sensation signals. Local anesthesia only numbs a small area of the body, and the patient remains fully conscious. This is mainly used for minor procedures, and medication is typically given by injection (however, topical forms also exist for mild cases). Some examples of local anesthetics include:

  • Benzocaine
  • Lidocaine
  • Mepivacaine
  • Bupivacaine
  • Ropivacaine
  • Epidural anesthetics
  • Spinal anesthetics

With general anesthesia, the patient is totally unconscious and unaware of the procedure taking place. General anesthesia is typically used for more serious operations, and the medication is given by IV injection or inhaled gas. Some examples of general anesthesia medications include:

Gases:

  • Sevoflurane
  • Desflurane
  • Isoflurane

IV Medication:

  • Propofol (Diprivan)
  • Thiopental
  • Ketamine
  • Etomidate

With the exception of very mild local anesthetic forms that are approved for home use (e.g., topical ointments), anesthesia must be administered by trained doctors or anesthesiologists. Anesthesia is important for patients undergoing surgery so that they are kept safe, relaxed, and pain-free. General anesthesia can cause retrograde and/or anterograde amnesia, which is when the patient temporarily doesn't remember events before or after receiving the anesthesia. It is the responsibility of an anesthesiologist or trained doctor to know the patient and to understand which form(s) of anesthesia is best.

Anxiolytics are often given during anesthesia to help alleviate anxiety in the patient and relax the body. These medications induce sleep and may cause anterograde amnesia as well. A common anxiolytic given by an anesthesiologist is midazolam (Versed). Paralytics may also be given during general anesthesia, once the patient is unconscious. These medications help with intubation, which allows the throat muscles to relax so a tube can be placed down the throat to facilitate breathing. At the end of the surgery, additional drugs are given to reverse the effects of the paralytics. Even though analgesics (painkillers) are not a form of anesthesia, they are often given postoperatively to help manage pain after the effects of anesthesia wear off.

Mechanisms of Action

Analgesic Mechanism

When a person is in pain, they may take an analgesic, or painkiller medication. The human body is composed of thousands of nerve cells that work with the nervous system to send messages or impulses to and from the brain. When cells in the human body are damaged or hurt, they release natural chemicals called prostaglandins. The nerve cells are very sensitive to prostaglandins, so when they sense the production of those compounds, they alert the brain about the pain and where it is located. The brain then tells the body how to respond to that pain. Analgesics work by preventing injured or damaged cells from producing and releasing prostaglandins. Once the cells stop producing this chemical, the brain stops receiving messages of pain. Because of this, the person's pain gradually lessens or even goes away.

If the pain requires a stronger form of relief, like an opioid or narcotic, the mechanism of action is different. Drugs such as morphine or oxycodone work by getting between the nerve cells. When taken or administered, opioids attach themselves to opioid receptors and pain receptors that are located on the outside of nerve cells in the brain, spinal cord, and other parts of the body. Once they are between the nerve cells, the opioids block messages of pain from traveling to the brain. The pain is muffled by the narcotics and a sense of pleasure floods the body, making the person relax.

Analgesics interfere with pain messages and impulses sent to the brain. If the brain does not know that the body is in pain, the person will not feel pain. However, these medications are not a cure for the pain and only provide temporary relief.


Opioid analgesics attach to opioid receptors on the exteriors of nerve cells and block the transmission of pain messages.

Image representing opioids attaching to an opioid receptor


Alike but Different

Have you ever had a joint that hurt, such as your knee? Do you recall what you took to relieve the pain? It may have been an over-the-counter drug, such as ibuprofen. But if you had to have surgery on that knee, ibuprofen would not have been enough to get you through the surgery; for that, you'd need something much stronger.

Now, do you recall what happened the last time you had a surgical procedure performed? You were likely given an injection of something that made you fall asleep pretty quickly. Then, a tube was inserted into your windpipe while a gas was turned on to keep you unconscious during surgery.

These are very different procedures with quite different purposes. One is called analgesia, and the other is called anesthesia. Let's define and delineate them now.

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What Is Analgesia?

Analgesia means the inability to sense pain. That's the really easy definition of it, but let's be a little more specific. In medicine, analgesia is a neurologic state or a pharmacologically induced state whereupon a painful stimulus is mitigated in part or in full. Meaning, the pain relief is at least partial, or it may be complete.

What I must emphasize for you is that analgesia refers to pain relief or the inability to sense pain without a loss of consciousness. You will find out that this is very different from anesthesia, although the two terms are, in part, related and often confused.

With analgesia alone, you are fully awake when you are given a pure analgesic that has no sedative properties. However, many pain relievers do have sedative properties that may make you drowsy, sleepy, or even unconscious.

The word analgesia comes from the prefix of 'an-,' which means without, and the suffix of '-algesia,' which means sensitivity to pain or a condition of sensitivity to pain. Thus, by just its roots alone, the word only implies without sensitivity to pain.

Some analgesics - drugs that cause analgesia - that have few to no sedative properties when used as intended and those that you may have heard of include:

  • Acetaminophen, found in Tylenol
  • Naproxen, the main component of Aleve
  • Ibuprofen, found in Advil
  • Lidocaine, the stuff your dentist injects before pulling your tooth

What Is Anesthesia?

Remember how I just said that analgesia provides pain relief without loss of consciousness? I hope so. Please remember that.

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Video Transcript

Alike but Different

Have you ever had a joint that hurt, such as your knee? Do you recall what you took to relieve the pain? It may have been an over-the-counter drug, such as ibuprofen. But if you had to have surgery on that knee, ibuprofen would not have been enough to get you through the surgery; for that, you'd need something much stronger.

Now, do you recall what happened the last time you had a surgical procedure performed? You were likely given an injection of something that made you fall asleep pretty quickly. Then, a tube was inserted into your windpipe while a gas was turned on to keep you unconscious during surgery.

These are very different procedures with quite different purposes. One is called analgesia, and the other is called anesthesia. Let's define and delineate them now.

What Is Analgesia?

Analgesia means the inability to sense pain. That's the really easy definition of it, but let's be a little more specific. In medicine, analgesia is a neurologic state or a pharmacologically induced state whereupon a painful stimulus is mitigated in part or in full. Meaning, the pain relief is at least partial, or it may be complete.

What I must emphasize for you is that analgesia refers to pain relief or the inability to sense pain without a loss of consciousness. You will find out that this is very different from anesthesia, although the two terms are, in part, related and often confused.

With analgesia alone, you are fully awake when you are given a pure analgesic that has no sedative properties. However, many pain relievers do have sedative properties that may make you drowsy, sleepy, or even unconscious.

The word analgesia comes from the prefix of 'an-,' which means without, and the suffix of '-algesia,' which means sensitivity to pain or a condition of sensitivity to pain. Thus, by just its roots alone, the word only implies without sensitivity to pain.

Some analgesics - drugs that cause analgesia - that have few to no sedative properties when used as intended and those that you may have heard of include:

  • Acetaminophen, found in Tylenol
  • Naproxen, the main component of Aleve
  • Ibuprofen, found in Advil
  • Lidocaine, the stuff your dentist injects before pulling your tooth

What Is Anesthesia?

Remember how I just said that analgesia provides pain relief without loss of consciousness? I hope so. Please remember that.

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