Miscellaneous analgesics

Miscellaneous analgesics are those analgesics that don’t fit into a particular class of analgesic because they work in a different way to relieve pain. That means they do not work like an opioid, nor do they work like an NSAID.

There are only really two miscellaneous analgesics currently available in the United States. They are acetaminophen and ziconotide.

Experts are not sure exactly how acetaminophen works but suggest it blocks a specific type of cyclooxygenase enzyme, located mainly in the brain.

Experts believe ziconotide works by blocking voltage-sensitive calcium channels located in the pain-sensing nerves of the spinal cord. This prevents over-firing of the nerve and decreases a person’s sensitivity to pain.

What are miscellaneous analgesics used for?

Acetaminophen is used to relieve pain caused by a wide variety of conditions, for example:

• headaches
• migraines
• osteoarthritis
• rheumatoid arthritis
• sprains and strains
• a toothache.

It may also be used to relieve pain caused by menstruation; however, it is not as effective as NSAIDs.

Ziconotide is reserved for people with severe chronic pain that has not responded to other pain-relieving medications.

What are the differences between miscellaneous analgesics?

There are a lot of differences between the two miscellaneous analgesics listed here, acetaminophen and ziconotide, with regards to the way they work, their uses, and their side effect profile. Acetaminophen is considered safe in children; however, the safety and efficacy of ziconotide has not been proven in children.

Are miscellaneous analgesics safe?

Acetaminophen has been associated with severe liver damage. The risk is increased if acetaminophen is taken at higher than recommended dosages, with other medications (such as cold and flu remedies) that also contain acetaminophen, or by people who drink more than three alcoholic drinks a day.

Ziconotide has been associated with severe psychiatric symptoms (such as hallucinations and paranoia) and cognitive impairment (such as disorientation and decreased mental acuity) and should not be used in people with a history of psychosis. Ziconotide should be stopped immediately if serious psychiatric symptoms occur. Ziconotide should also not be used in people with kidney or liver disease and caution should be observed when using in elderly people. Ziconotide is not recommended for use in children.

What are the side effects of miscellaneous analgesics?

Generally, acetaminophen is well tolerated, and few people experience side effects. One of the more common side effects is fever (that was not present before treatment and not caused by the condition being treated).

Other side effects that have been reported rarely with acetaminophen include:

• a rash
• a sore throat
• sores or ulcers on the lips or mouth
• unusual tiredness or weakness
• urine or stool changes.

Some of the more common side effects that have been associated with ziconotide include:

• ataxia (difficulty coordinating muscle movements)
• blurred vision
• confusion
• dizziness
• drowsiness
• gastrointestinal disturbances (such as diarrhea, nausea or vomiting)
• hallucinations (may be auditory or visual)
• a headache
• increased creatine phosphokinase levels (an indicator of muscle tissue damage)
• memory impairment
• walking abnormalities
• weakness.

For a complete list of side effects, please refer to the individual drug monographs.