Analgesics are medications that prevent the body from feeling pain. They work by either stopping pain signals from reaching the brain or altering the brain’s interpretation of those signals. Although analgesics block pain, they do not treat the underlying condition that is responsible for the pain.
They are used to treat pain related to many conditions, including:
- Arthritis and other types of joint pain
- Back pain, including herniated discs, degenerative disc disease and spinal stenosis
- Whiplash, burns and other types of trauma pain
- Chest pain, abdominal pain and pelvic pain
- Labor and surgical pain
- Orofacial pain and dental pain
- Chronic pain disorders such as fibromyalgia, chronic fatigue syndrome and lupus
- Sickle cell anemia crises
- Cancer pain
Narrowly defined, analgesics include opioids such as codeine and non-narcotic painkillers such as acetaminophen. However, many other classes of drugs are also used to relieve pain. Among these are anti-inflammatories, which include corticosteroids such as hydrocortisone, and nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, naproxen and COX-2 inhibitors.
Some medications that primarily treat other conditions are also used to reduce pain. For example, antidepressants treat many pain conditions, lithium can be prescribed as a preventive headache medication, anticonvulsants (seizure medications) relieve conditions ranging from cranial neuralgias to restless leg syndrome to diabetic neuropathy, antihistamines can treat conditions including headaches and chest pain, anti-malarial and chemotherapy drugs sometimes ease lupus, and antihypertensives (blood pressure drugs) can be prescribed for headaches, chest pain or benign prostatic hyperplasia.
Other classes of drugs that can be used to relieve pain conditions include muscle relaxants, immunosuppressives such as DMARDs and biologic response modifiers, psychostimulants, marijuana-like cannabinoids, nerve blocks and other anesthetics used in injection therapy, antibiotics and other antimicrobials for conditions ranging from Lyme disease to Reiter’s syndrome, and digestive-tract medications such as antispasmodics and proton pump inhibitors for abdominal and chest pain.
Substances being studied for use in pain relief include the wrinkle treatment botulinum toxin A (Botox), which studies have shown to be promising against conditions including migraines, orofacial pain and tennis elbow; supplements such as glucosamine and chondroitin; and sugar, which has been found to reduce pain in children.
Analgesics can be administered in several ways, including:
- Oral. Delivered in liquid or pill form.
- Creams, gels or ointments. Topical analgesics applied over painful areas.
- Skin patch. A bandage-like patch that gradually and continuously releases medicine through the skin over two or three days.
- Suppository. Medicine that dissolves in the rectum and is absorbed into the body.
- Intravenous. Injection into a vein.
- Subcutaneous. Needle placed just under the skin.
- Continuous infusion. The slow introduction of a fluid into a blood vessel, usually over a prolonged period of time.
- Pump. Known as patient-controlled analgesia (PCA), a pump allows a patient to push a button that delivers a preset dose of medication.
- Intrathecal. Needle placed into fluid around the spinal cord.
- Epidural. Needle placed into space around the spinal cord.
Patients who have chronic pain will usually receive long-acting analgesics regularly according to a schedule. This is often done even if it requires waking the patient. Patients should not experience any pain before the next dosage is administered and should consult their physician if treatment is not controlling their pain
Types and differences of analgesics
Analgesics are available in one of two primary forms: non-narcotic and narcotic.
Non-narcotic analgesics are milder forms of the painkillers that include acetaminophen. It works by preventing the production of prostaglandin, a substance that sensitizes pain receptors as a means of stimulating pain and inflammation.
By interfering with the role of prostaglandins, a patient’s perception of pain is reduced. Acetaminophen is found in hundreds of over-the-counter medications. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) are not technically analgesics according to some definitions. However, because they share many of the same properties, they are treated as such for the purpose of therapy. Examples of non-narcotic analgesics include:
- Aspirin and other salicylates
- COX-2 inhibitors
Many other non-narcotic drugs have analgesic effects. For example, the only drugs approved by the U.S. Food and Drug Administration to relieve painful diabetic neuropathy are an antidepressant and an anticonvulsant (seizure medication).
Narcotic analgesics (opioids) are strong analgesics that can be used when pain signals are too severe for non-narcotic analgesics to control. These drugs work on the central nervous system to relieve pain. In some cases, they are also given just before or during an operation to help increase the effectiveness of an anesthetic. The dosage level of a narcotic is closely controlled by a physician so that it is just enough to relieve the pain. Dosage levels can be adjusted as necessary.
Narcotic analgesics include:
There is also an analgesic called tramadol that may be considered an atypical opioid.
In some cases, a narcotic analgesic may be used in combination with a non-narcotic analgesic to increase the pain-killing effect. Such combinations may also have the benefit of requiring a lower amount of each drug to be effective, thus minimizing the side effects of each medicine.
Most medical societies have made recommendations to use a stepwise approach for pain medications depending upon the severity of the pain.
Conditions of concern
Certain medical conditions may affect the use of individual analgesics and analgesic combinations. Patients should inform their physician of any of the following:
- Asthma, allergies or history of nasal polyps
- Brain disease or head injury
- Emotional problems or mental illness
- Emphysema or other chronic lung disease
- Enlarged prostate or problems with urination (dysuria)
- Gallbladder disease or gallstones
- Heart disease
- Hemophilia or other bleeding problems
- History of alcohol or other drug abuse
- History of convulsions (seizures)
- Kidney disease
- Liver disease
- Overactive or underactive thyroid gland (hyperthyroidism or hypothyroidism)
- Stomach ulcer or other stomach problems
- Vitamin K deficiency
- Side effects
Potential side effects
When analgesics are used in moderation and according to a physician’s orders, they can provide relief from pain. However, these drugs can have some side effects, especially when taken in large doses. These include:
- Dizziness or lightheadedness
- Nausea and vomiting
- Dry mouth
Over time, a patient can build up a tolerance to narcotic(opioid) analgesics. This means that the patient will need to take more of the drug to obtain the same pain-relieving effect. In addition, opioid analgesics can become habit-forming and cause physical dependence, which means the patient would have withdrawal symptoms if the drug is stopped abruptly. Opioids can also cause addiction, which is usually considered psychological dependence.
Patients who stop taking opioids may find that their body goes through a period of adjustment as it withdraws from the drug. For this reason, patients should not quit taking analgesics unless instructed by their physician. Side effects associated with withdrawal from analgesics include.
Patients who stop taking narcotic analgesics may find that their body goes through a period of adjustment as it withdraws from the drug. For this reason, patients should not quit taking analgesics unless instructed by their physician. Side effects associated with withdrawal from analgesics include:
- Body aches
- Goose pimples
- Increased sweating
- Increased yawning
- Loss of appetite
- Nervousness, restlessness or irritability
- Runny nose or sneezing
- Shivering or trembling
- Stomach cramps
- Trouble sleeping
- Weakness or fatigue
In recent years, there has been controversy over the potential for addiction in patients who use narcotic analgesics. Many physicians are reluctant to prescribe these painkillers, and many patients are reluctant to take them, because they fear addiction. Opioid medications rarely cause addiction when used correctly under a physician’s close supervision for acute pain and cancer pain. However, there is a risk of addiction when they are used to treat chronic pain even in patients with no history of drug abuse.
Although non-narcotic analgesics do not typically cause addiction or dependence, they may trigger other side effects in some patients, especially if taken in large doses. For example, large doses of NSAIDs can cause internal bleeding.
In addition, patients are advised to consult a physician before using any non-narcotic analgesic. The fact that many of these drugs are available in over-the-counter form does not mean that they are not potentially dangerous. For example, topical analgesics can cause serious burns when combined with heat treatments (thermotherapy), and misuse of acetaminophen is a leading cause of liver failure.
Drug or other interactions
Before using analgesics, patients should inform their physician if they have ever had an allergic reaction to any opioid, acetaminophen, or aspirin or other salicylates. Patients should also tell their physician if they have ever had a reaction to any of the following drugs:
- Flurbiprofen, oral
- Mefenamic acid
- Tiaprofenic acid
Use of prescription and nonprescription analgesics that contain an opioid, or aspirin or another salicylate, may cause an overdose when combined with analgesics used to treat cancer pain. Other medications that can affect treatment with analgesics include:
- Central nervous system (CNS) depressants
- Diarrhea medicine
- Oral diabetes drugs (antidiabetic agents)
- Urinary alkalizers
Patients taking analgesics should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Patients should also report any allergies to other substances such as foods, preservatives or dyes. Alcohol and other CNS depressants should not be used with analgesics. Examples of CNS depressants include:
- Antihistamines or other allergy medications
- Antiseizure medications (anticonvulsants)
- Cold medications
- Muscle relaxants
- Any prescription pain medication
- Sedatives, tranquilizers or sleeping pills, including benzodiazepines
Other medications that may adversely interact with analgesics include:
- Rifampin (Rifadin, Rimactane), an antibiotic used primarily to treat tuberculosis
- Sulfinpyrazone (Anturane), a gout medication
- Vitamin supplements
- How to use
Pregnancy use issues
Women who are pregnant should approach using analgesics with caution. For example, though studies in humans have not conclusively shown that aspirin can cause birth defects, they have been found to cause birth defects in animal studies.
In humans there have been reports of low birth weight and possibly death in newborns whose mothers took large amounts of aspirin late in pregnancy. Women should not take aspirin during the last three months of pregnancy without a physician’s approval. Too much aspirin late in pregnancy has also been associated with:
- Bleeding problems in the fetus before or during delivery
- Increase in length of pregnancy
- Prolonged labor
- Severe bleeding in the mother before, during or after delivery
Opioids prolong labor. They have been shown to produce birth defects in animals, but this has not been confirmed in people. However, mothers who use too much of a narcotic during pregnancy risk creating a drug dependency in the fetus. The newborn baby may suffer withdrawal symptoms after the birth. Opioids can also cause breathing problems in the newborn if the mother takes the medication just prior to or during delivery.
Some opioids, such as certain codeines, have been shown to pass into breast milk.
Child use issues
Children and teens with fever or other viral infection (especially flu or chickenpox) should not take aspirin, as it may cause a rare but serious illness known as Reye’s syndrome. In addition, children may be more vulnerable to the side effects of aspirin than adults.
Children who use opioids may experience breathing problems, or unusual excitability or restlessness.
However, these potential complications do not prohibit physicians from prescribing analgesics to children. The American Academy of Pediatrics (AAP) has stated that too often, analgesics are not prescribed when they could be of great benefit in relieving the pain of pediatric patients.
The organization is also concerned that the U.S. Food and Drug Administration (FDA) has not considered or approved many potent analgesics for use in children. The AAP has stated that analgesics can be of great benefit to children when prescribed at dosage levels appropriate for the child’s body weight and physiologic development, and the medical situation.
According to the FDA, common pediatric uses of opioids include acute trauma or illness, burns, surgery and procedures, mechanical ventilation, cancer pain and sickle cell anemia crises.
Elderly use issues
Elderly patients may be more susceptible to side effects associated with analgesics, particularly breathing problems, drowsiness, constipation and liver dysfunction.
Symptoms of medication overdose
An overdose of either opioid or non-narcotic analgesics is potentially life-threatening. Patients exhibiting any of these symptoms should contact their physician immediately:
Questions for your doctorPatients may wish to ask their doctor the following questions about analgesics:
- What are analgesics, and how can they help manage my pain?
- Which nonprescription analgesics are the safest and most effective for me to use at home?
- When over-the-counter analgesics do not stop my pain, which prescription analgesics would you recommend?
- How should the analgesic you are prescribing for me be administered?
- Can this medication be addictive for me? Would a family or personal history of addiction influence your decision to prescribe me this medication?
- For how long can I safely take this analgesic?
- What side effects might I experience?
- At what point should I notify you of side effects?
- Do I need to take special precautions when using analgesics?
- Can other treatments such as exercise, massage or heat therapy reduce my need for analgesics?