Analgesics

Analgesics are medicines that are used to relieve pain. They are also known as painkillers or pain relievers. Technically, the term analgesic refers to a medication that provides relief from pain without putting you to sleep or making you lose consciousness.

Many different types of medicines have pain-relieving properties, and experts tend to group together those medicines that work in a similar way. Two of the most common groups of pain killers are nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids (narcotics), but there are many more.

What are analgesics used for?

Analgesics may be taken to relieve pain that arises from a wide range of conditions, such as:

• appendicitis
• cancer
• congenital conditions such as curvature of the spine
• fibromyalgia
• gallbladder disease
• gastrointestinal disorders
• headaches
• improper lifting techniques
• infection
• menstruation
• migraines
• multiple sclerosis
• nerve damage
• osteoarthritis
• pain syndromes
• poor posture
• rheumatoid arthritis
• sprains
• strains
• surgery
• trauma
• toothache
• wound cleansing and debridement.

It is important to note that not all analgesics are appropriate for all these conditions.

What are the differences between analgesics?

Analgesics differ in the way they work and, in their potency, (how strong they are). There are also differences in the way they are absorbed, distributed, metabolized and excreted within the body.

Within the same class of analgesic (for example NSAIDs), there are differences in their likelihood for side effects, potency, and the way they need to be taken (for example, by mouth, applied topically, by injection).

Below, we have listed seven different classes of analgesics:

1. Analgesic combinations (includes narcotic analgesic combinations)
2. Antimigraine agents
3. Cox-2 inhibitors
4. Acetaminophen and miscellaneous analgesics
5. Narcotic analgesics
6. Nonsteroidal anti-inflammatory drugs (NSAIDs)
7. Salicylates.

1. Analgesic combinations, including narcotic analgesic combinations

Description: Contain analgesics in combination with other analgesics, or with other substances that enhance the analgesic effect (such as caffeine) or induce sleep or other desired effects. Includes narcotic analgesic combinations.

Table: Common analgesic combinations (including narcotic analgesic combinations) available in the U.S.

2. Antimigraine agents

Description: These medicines are used to relieve the pain that arises from migraine headaches. There are several different classes of drugs that can relieve a migraine such as ergots, triptans, and NSAIDs. Some are available in combination with caffeine (caffeine can enhance the effectiveness of other ingredients and has analgesic properties).

Table: Common antimigraine analgesics available in the U.S.

3. Cox-2 inhibitors

Description: Cox-2 inhibitors are a type of nonsteroidal anti-inflammatory drug (NSAID) that specifically blocks COX-2 enzymes. COX-2 enzymes are responsible for releasing prostaglandins after infection or injury. NSAIDs that favor COX-2 enzymes have a higher risk of cardiovascular effects but less gastrointestinal effects.

Table: List of Cox-2 inhibitors available in the U.S.

4. Acetaminophen and miscellaneous analgesics

Description: Miscellaneous analgesics are ones that are unique in the way that they work. An example is acetaminophen, which is still thought to work on cyclo-oxygenase (COX) enzymes, but in a different way to NSAIDs.

Table: List of miscellaneous analgesics available in the U.S.

5. Narcotic analgesics

Description: Narcotic analgesics work by binding to opioid receptors, which form part of the opioid system that controls pain, pleasurable and addictive behaviors. The main opioid receptor that narcotic analgesics bind to is the mu receptor.

Table: List of common narcotic analgesics available in the U.S.

6. Nonsteroidal anti-inflammatory drugs (NSAIDs)

Description: NSAIDs block cyclo-oxygenase enzymes which are responsible for the production of prostaglandins.  NSAIDs that favor COX-1 enzymes are more likely to cause gastrointestinal side effects; those that favor COX-2 enzymes have a higher risk of cardiovascular effects but less gastrointestinal effects.

Table: List of common nonsteroidal anti-inflammatory drugs (NSAIDs)

7. Salicylates

Description: These are substances that are found naturally in some plants (such as white willow bark and wintergreen leaves) or derived from salicylic acid. Not all have pain relieving effects, some are used as food preservatives and antiseptics. Those that do relieve pain work in a similar way to NSAIDs.

Table: List of common salicylates with analgesic effects

Are analgesics safe?

Most analgesics are considered safe when taken for short periods of time and exactly as directed on the packaging or by a doctor. Some analgesics, such as ibuprofen and acetaminophen, are considered safer than others.

Narcotic analgesics and narcotic analgesic combinations have been associated with some serious risks such as respiratory depression (unusually slow and shallow breathing), opioid-use disorder, and potentially fatal overdose. They are potentially addictive and should only be used for certain conditions and under strict monitoring.

NSAIDs have also associated with some serious side effects, such as an increase in the risk of fatal heart attack and stroke. Some NSAIDs, such as diclofenac and celecoxib, are more likely to increase this risk than others and NSAIDs should never be used just before or after heart bypass surgery (coronary artery bypass graft, or CABG). Other NSAIDs, such as ketorolac, aspirin and indomethacin, are associated with a higher risk of gastrointestinal side effects. Most NSAIDs are not suitable for children or adolescents under the age of 18 years. Ibuprofen is the only NSAID approved for children aged three months and older.

What are the side effects of analgesics?

All medicines have side effects but how vulnerable a person is to them depends on several different factors such as age, genetics, kidney function and gender (see managing common drug side effects)

Narcotic analgesics have many side effects, although people with cancer or terminal illness taking narcotics for long periods of time may become tolerant to some of these side effects.

Drowsiness, sleepiness, or dizziness is common with most narcotic analgesics. This can affect driving or a person's ability to operate machinery and perform other hazardous tasks. Alcohol may potentiate these effects. See narcotic analgesics for other commonly reported side effects.

NSAIDs may also cause side effects, especially when used at higher than recommended dosages for long periods of time. Gastrointestinal side effects that may occur include bloating, diarrhea, constipation, irritation of the lining of the stomach, nausea or vomiting. NSAIDs may also affect kidney function and reduce how quickly blood flows through the kidneys. They may cause retention of sodium and water which can lead to edema and high potassium levels. Occasionally, they may cause more serious damage to the kidneys. See NSAIDs for other commonly reported side effects.