Drugs for pain!!!Miss Katy Davidson, BSc (Hons)

Jason

WHO Pain ladder

Paracetamol

The exact mechanism of action for Paracetamol is unknown, although it is thought to selectively inhibit COX-2.

Used in mild pain relief and has a mild antipyretic effect.

What happens in a paracetamol overdose?

Overdose

NSAIDs

COX-1 and COX-2 Inhibitors. Inhibits the synthesis of prostaglandins and thromboxanes.

There are several different classes of NSAIDs, but they may not be worth learning…

Examples include: Ibuprofen, aspirin, diclofenac, naproxen

Complications

Action on COX-2 gives your anti-inflammatory, antipyretic and analgesic effects

Action on COX-1 gives you problems…

Inhibition of COX-1 reduces synthesis of PGE2 in the stomach which in turn increases the amount of acid secretion and decreases the amount of bicarbonate secretion.

How can this be countered?

Omeprazole and taking NSAIDs with food, care to be taken when prescribing to patients with heartburn/previous gastroduodenal ulcers

COX-2 selective

Supposed to have fewer side effects as they do not target COX-1

Examples include:

Celecoxib

Etoricoxib

This is all you really need to know

Mild opioids

Codeine

Dihydrocodeine

C0-codamol

Used for moderate pain upward

Broadly work on the mu, kappa and delta opioid type receptors

Common side effects?

Likely to cause constipation, especially in the elderly, at high doses or with long term use

How is this countered?

Avoid long term use if possible and co-prescribe laxatives in high risk patients.

Strong opioids

Morphine

Diamorphine

Tramadol

Used in severe pain

Can be highly addictive

Often cause problems with overdose

Opioid overdose

Symptoms?

Pin-point pupils (possibly), respiratory depression, tachycardia, hypotension, nausea/vomiting

How do you treat it?

Give IV naloxone, an opioid receptor antagonist

Occasionally Naltrexone may be given (longer acting)

Partial/mixed opioids

Opioid addiction

Buprenorphine – Also used in opioid addiction alongside methadone

Pentazocine

Need to be aware of them

Neuropathic pain

First line is normally TCAs i.e. amitriptyline/nortryptyline or duloxetine (SNRI)

Second line is both of these combined

Third line is gabapentin/pregablin

Carbamazepine is often used in the treatment of trigeminal neuralgia

The end Get out