Analgesics

By | October 26, 2017
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What do they do?
Analgesics are drugs designed specifically to relieve pain. There are several types of analgesics: acetaminophen (Tylenol), which is available without a prescription, and a variety of opioid analgesics, which are available only with a prescription. Some products combine acetaminophen with an opioid analgesic for added relief.

How do they work?
Opioid (also called narcotic) analgesics work by binding to receptors on cells mainly in the brain, spinal cord and gastrointestinal system. Opioids are often very effective against pain, but they also carry a greater risk of side effects than acetaminophen.

Who are they for?

Analgesics are for anyone with pain, and that includes almost everyone with arthritis or a related condition.  Doctors once reserved opioids (also called narcotics) for treating severe acute pain, such as that from surgery or a broken bone but in more recent years, opioids have been increasingly prescribed for chronic pain, such as pain from arthritis. Unlike NSAIDS, opioids don’t cause gastrointestinal bleeding; they may be a better alternative for people who cannot take NSAIDs due to allergies or kidney or liver issues.

But opioid use for chronic (non-cancer) pain is controversial because they’re associated with a high risk of abuse, addiction and accidental overdose.  Certain factors predict the suitability of long-term opioid use for individuals with chronic pain. A tool called DIRE (Diagnosis, Intractability, Risk and Efficacy) helps doctors to assess those factors – including the patient’s cause of pain, psychological health, chemical health and social support. A high composite score suggests the person is likely to gain the greatest benefits from opioid analgesics with the least risk of adverse effects. Opioid analgesics are not appropriate for people at risk of addiction.

What’s important to know about the drug class?
While some analgesics are taken as needed, others must be taken at regular intervals to keep down pain. If your doctor prescribes an opioid analgesic, be sure you know how to take it – and when. And never stop taking it abruptly because doing so can cause withdrawal symptoms such as anxiety, sweating, nausea and insomnia.

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Although some people may benefit from taking acetaminophen in addition to an NSAID for added pain relief, you should always speak with your doctor before combining any medications, even those without a prescription.  Also, it is important to speak with your doctor before combining an opioid analgesic and acetaminophen. Because many analgesic products already combine an opioid with acetaminophen, taking over-the-counter acetaminophen along with your medication could cause you to get a dangerously high dose.

When first starting an opioid analgesic avoid driving a car or other tasks that require concentration until you know how you react to the drug. Some people experience drowsiness or dizziness with analgesics.

If you don’t like taking pills, speak to your doctor about a patch that delivers a continuous does of an opioid medication through the skin.

Types of analgesia

  • Paracetamol

Good for mild to moderate pain. Use iv route in severe acute pain.

Contraindicated in severe hepatic impairment, dose reduce in mild impairment (e.g. 500mg QDS).

Generally safe (except in overdose) and can be used in pregnancy

Prescribe: Paracetamol 1g four times a day orally

Regular is better than PRN as paracetamol acts in conjunction with other analgesia (e.g. opiates) to increase efficacy

  • NSAIDS

Very good in inflammatory or musculoskeletal pain. Consider alternative routes e.g. topical/PR.

Contraindicated in peptic ulcer disease, previous hypersensitivity to NSAIDs or aspirin, severe heart failure and pregnancy. If using long term monitor renal and liver function regularly.

Prescribe: Ibuprofen 200-400mg orally up to four times a day PRN

If using regularly cover with a proton pump inhibitor (PPI) such as omeprazole (20mg orally once a day).

  • Weak Opioids 

Codeine

  • Strong Opioids

g. Morphine, oxycodone, fentanyl

Remember tramadol now classed as strong opioid

  • Neuropathic Agents

Usually antidepressant or antiepileptic drugs and often work well as an adjunct to the analgesia above.

First line: amitriptyline (e.g. 10mg ON), duloxetine, gabapentin or pregabalin (see national/local prescribing guidelines).

Tramadol has some neuropathic properties and can be used for acute rescue therapy

  • Others

Benzodiazepines, steroids, lidocaine, bisphosphonate, baclofen, hyoscine butylbromide, ketamine

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Advice from local pain or specialist palliative care services should be sought when considering these options

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