Analgesics

Overview

Analgesics are medications used to reduce pain. There are many types of pain medications each with a different mechanism of action. Some of them have other properties, such as the ability to reduce fever or inflammation, and others are used to treat conditions unrelated to pain such as seizures or depression.

Acetaminophen (Tylenol®)

This medication is in its own class. It is an analgesic as well as an antipyretic, meaning it reduces fever in addition to treating pain. It can be extremely effective at treating mild to moderate pain.

Nonsteroidal anti-inflammatory drugs (NSAIDs)

These are analgesics that have pain-killing as well as anti-inflammatory properties. They are available in both over-the-counter as well as more potent, prescription-only formulations. They function by inhibiting the enzyme cyclooxygenase (COX), which participates in the genesis of inflammation and sensitizes nerve endings, making them more likely to produce pain. They are excellent relievers of mild to moderate pain, and are generally most effective at relieving pain with an inflammatory component, such as that from tissue injury, arthritis, infection, etc. Ibuprofen, piroxicam, celebrex®, and meloxicam are all examples of NSAIDs.

Opiates

Opiates, also called narcotics, are the oldest pain medications known. Derived from poppy extracts, they directly inhibit the transmission of pain within the central nervous system. Unfortunately, they have a variety of side effects, such as substance abuse potential, constipation, respiratory depression, and lethargy. When used appropriately, these medications can be powerful tools in the management of chronic pain. Morphine, hydrocodone, Fentanyl®, and oxycodone are all examples of opiate medications.

Tricyclic Antidepressants (TCAs)

These are medications originally designed to treat depression. They work by increasing the body’s levels of the neurotransmitters epinephrine, norepinephrine, and serotonin. Not only are these neurotransmitters important for the regulation of mood, they also control neuronal pathways that inhibit pain. They appropriate for patients with depression alone, pain alone, or depression and pain in combination. Generally, patients take TCAs at bedtime, as they can cause somnolence for several hours. Dry mouth and blurry vision are other side effects sometimes experienced by patients after taking them. They should not be taken concurrently with serotonin reuptake inhibitor antidepressants (SSRIs), nor should they be taken by patients with cardiac arrhythmias or thyroid problems. Patients who take TCAs need to have periodic electrocardiograms to check for conduction abnormalities in the heart. Amitryptiline, nortryptiline, and imiprimine are all examples of tricyclic antidepressants.

Anticonvulsants

These are medications originally used to treat seizures. In general they slow down the activity of irritable nerve cells. In the brain, such irritability can result in a seizure; in the peripheral nervous system, such irritability can result in pain. Thus, these medications, by inhibiting this abnormal nerve cell activity, treat either seizures or pain. Neurontin®, Lyrica®, Trileptal®, and Keppra® are all examples of anticonvulsant medications used to treat pain.

References

Przewlocki R, Przewlocka B. Opioids in neuropathic pain. Curr Pharm Des 2005;11:3013-25.

Saarto T, Wiffen PJ. Antidepressants for neuropathic pain. Cochrane Database Syst Rev 2005;3:CD005454.
Wiffen P, Collins S, McQuay H, Carroll D, Jadad A, Moore A. Anticonvulsant drugs for acute and chronic pain. Cochrane Database Syst Rev 2005;3: CD001133.