Pharmacological

Pain Management (from //Pharmacology for Health Professionals pg 283 - ??//)

P: palliative of provocative factors - what makes the pain better/worse Q: quality - What is the pain like? burning, nagging... R: radiation - where does it hurt? Does the pain go anywhere else? S: severity - how severe is it? How much does it hurt? T: timing - does the pain come and go? What brings it on? How long does it last?
 * Measurement of pain:**

Different scales (insert picture) can also indicate severity of pain. For children, pictoral scales can be used with faces to 'show how much it hurts'..

Physical assessment focusing on tender areas and the patients response to movement and stretch can aslo assist in an acurate diagnosis.

Be watchful of non-verbal indicators suchs as wincing, flinching...

Important principles of pain management include:
 * General Principles**
 * Treat the __cause__ of pain where possible, not just the symptom
 * Make accurate diagnosis and assessment of pain extent and type to ensure appropriate analgesic prescription (i.e. traditional analgesics for nociceptive pain, anticonvulsants and antidepressents with opiods for neuropathic pain, and a 'whole patient' multimodal approach for cancer pain of psychogenic pain)
 * Keep the patients pain free. Patients recover faster is pain is relieved. Patients should not have to suffer pain before the next dose of analgesic; pain should be anticipated and prevented rather than //reacted to//. Analgesic effect should be optimised, starting with a low dose and increasing the dose depending on the patient's response and adverse effects. In prescription notation, the dose should be 'QS' (sufficient quantity), not PRN.
 * Dose at regular specified intervals: particularly for chronic pain. Analgesics should be given on a regular fixed time basis to avoid pain, to optimise drug blood levels and to reduce the conditioning reaction in which periods of pain lead to drug-seeking behaviour.
 * Avoid the chronic pain stress cycle and 'sick role'. Minimise pain-related disability with review of __all__ related factors, and provide reassurance and explanations. For example, an antidepressant may help stabilise sleep patterns and enhance analgesia, whereas sedatives and tranquillisers may impair participation in pain management programs.
 * __Stepwise management__- doses should be stepped up the 'analgesic ladder' as required for increasing painor development of tolerance (insert figure 15.5)
 * Step 1 - for mild pain, start with non-opioids (aspirin, paracetamol) with or without adjuvant drugs (antidepressants...)
 * Step 2 - for mild - moderate pain, substitute or add a low dose opioid (morphine as slow release tablets, tramadol capsules...)
 * Step 3 - for moderate to severe pain, increase the dose of opioid, with adjuvant drugs
 * Prevent adverse effects of opioids - rather than allowing adverse effects to occur and then treating them. For example
 * Develop a patient management plan - intefrate analgesia into a comprehensive patient management plan with a multidiciplinary approach, combination therapy, and involvement of a pain-control team if appropriate.

Some of the reasons for under-treatment of pain include:
 * Avoiding under-treatment of pain**
 * Fear of inducing addiction to opioids - this leads to many patients being inadequately treated for pain, and instead developing a pattern of drug-seeking behaviours to achieve adequate pain control. The risk of addiction in hospitalised patients with severe pain recieving opioids at regular intervals is minimal.
 * Fear of tolerance to opioids - tolerance is not generally seen in 'opioid-naive' patients with severe or acute chronic pain, generally an increase in pain is related to disease progression or complications.
 * Fear of inducing respiratory depression - with careful monitoring and assessment, the potential for this is low.
 * Under-assessment of pain - and personal biases on the administration of pain medications. There may be a discrepancy between the health-care provider's and the patient's estimate of pain severity. Women under 50, people over 70 and minority groups are often under treated for pain.
 * Fear of legal regulation of opioids - due to their potential for abuse and illegal diversion, laws strictly monitor and regulate opioid avalability, prescription and use.
 * The wish to reserve stronger analgesics for later use - in case pain becomes more severe.


 * Routes of administration**
 * Oral - this is the simplest and most acceptable route, and has the advantage of minimising the risk of IV complications. Opioid drugs may undergo significant hepatic metabolism (first pass effect) and so higher doses are required than parenteral administration. Sustained-release preparations help prolong the half-life of morphine from 3-4 hours to 12-24 hours and are useful for stable chronic pain.
 * Continuous infusion of opioids - via SC or IV routes - this is common where there is vomiting, where severe pain cannot be relieved orally, or post-operatively. Opioids may be infused by a microdrip infusion set and pump (what the..?) or by patient -controlled analgesia (PCA). PCAs are commonly used post-surgery, in a hospice setting, or for chronic cancer sufferers.
 * IV route is the fastest route for rapid pain control as it avoids the absorption phase.
 * The rectal route is useful in patients who cannot swallow or who are vomiting, and for slower absorption.
 * Transdermal administration is effective for chronic administration or lipid-soluable drugs
 * Fentanyl patches are available for patients who cannot tolerate morphine
 * Nitrous oxide and other gases can be administered by inhalation

The most commonly used opioid is morphine. Adverse drug reactions: the most serious being respiratory depression, excessive sedation, dysphoria, constipation, nausea, vomiting, tolerance and dependence. Drug **tolerance** is defined as the gradual decreas in the effectiveness of a drug given repeatedly over a period of time. If tolerance develops, higher doses are required to achieve the same effect. Tolerance develops to the an algesic effects, as well as to sedation, nausea and vomiting that opioids cause. However, tolerance does not develop to constipation, nightmares, confusion and hallucinations, so these adverse reactions may become more of a problemas doses are increased. Other common opioids include:
 * Pharmacological pain management**
 * Analgesic drugs**
 * Opioids**
 * Codeine - abosorrbed well after oral or parental administration
 * Fentanyl - very potent with a short duration of action. IM, slow IV, lozenge (lollipop) or patch dosage
 * Methadone - analgesic properties similar to morphine, but has extended half life and better oral bioavailability
 * Pholcodine - virtually no analgesic effects, but good for treatment of nausea, cough supression...
 * Tramadol - synthetic analgesic, not related to opioids. It is used in the treatment of moderate - severe pain, but is less effective and more expensive than morphine. However there is lesser potential for respiratory depression and drug dependency. Common adverse reactions include dizziness, nausea, hypertension and seizures.
 * Pethidine - effective for short term use but is not suitable orally due to low bioavailibility. It is less apt at releasing histamines or raising biliary tract pressure, and so it is often prescribed to patients with acute asthma or pancreatitis. There are dangerous effects for long-term use, and so it should only be prescribed for short-term analgesia.
 * Hydromorphone - semi-synthetic opioid with a faster onset but a shorter duration of action than morphine.
 * Oxycodone - potent synthetic opioid up to 10 times more potent than codeine. It is effective as a nighttime suppository dosage in patients unable to swallow.
 * Dextropropoxyphene - synthetic analgesic suitable for treatment of mild to moderate pain. There are significant side effects associated with this drug including accumulation and cardiotoxicity, and there are no marked advantages over safer analgesics such as codeine, aspirin and paracetamol, and so its use is not recommended.
 * Heroin - the case is often put forward for the legislation of heroin for treatment of intractable pain because of its analgesic and euphoric effects. Some argue it is more potent, faster acting and produces a more prolonged analgesic and euphoric effect than other analgesics. Due to its greater lipid-soluability, heroin crosses the blood-brain barrier faster than morphine does, inducing a greter 'rush', this is why it is preferred by opioid-dependent people, however it has a shorter duration of action. Heroin is classified as a schedule 9 drug, and is a popular drug of abuse. There is additional fear associated with legislating it, such as an increased risk of drug diversion, pharmacy burglaries and crime. As heroin offers few (if any) advantages over the already marketed options, it is Australian policy that heroin is not acceptable for use in treatment of pain.

Typified by aspirin. These drugs have significant anti-imflammatory and antipyretic (antifever) actions but do not possess the steroidal chemical structure of anti-inflammatory cortico-steroids, and are known as __non-steroidal anti-inflammatory drugs__ (NSAIDs). These drugs also have anti-platelet actions which decreases the risk of thrombosis. Themain drugs in this classification include aspirin and paracetamol, ibuprofen, indomethacin, diclofenac and newer soecific cyclo-oxygenase-2 inhibitors. Asparin and paracetamol are effective for mild to moderate pain and are often combined with opioid analgesics to enhance pain control in patients with moderate to severe pain.
 * Non-opioid analgesics - the NSAIDs**

Adverse reactions include gastrointestinal tract disorders (dyspepsia, nausea and vomiting, diarrhoea/constipation), renal damage, asthma attacks, skin reactions, sodium retention and consequent heart failure and hypertension. Large overdoses of paracetamol can cause fatal acute liver damage if not promptly treated.

Aspirin vs Paracetamol Aspirin is readily available OTC. It can be used in stroke prevention due to its anti-platelet qualities. In normal doses, paracetamol is a safer OTC analgesic than aspirin for the following reasons:
 * adverse effects and allergic reactions are rare with therapeutic doses
 * there is low risk of gastic upset, renal impairment or peptic ulceration compaired with aspirin
 * plasma protein binding is negligible (no risk of displacement causing drug interactions)
 * few serious adverse drug interactions
 * may be used by children
 * safe to use duing pregnancy and lactation

Compound analgesics Simple analgesics such as paracetamol, are sometimes formulated with other drugs (such as antihistamines, opioids, caffeine, anatacids) to combine the pharmacological actions of two or more drugs. Examples include: GABA analogues - useful for treatment of neuropathic pain Capsaicin - found in chilli peppers and is formulated into a cream for arthritic pain and HIV infection Local anasthetics (e.g. lignocaine) General anasthetics (e.g. halothane, nitrous oxide) Ethanol or phenol - injected near sensory nerve fibres (rarely carried out any more) Cannabinoids - enhances analgesic property of morphine (being exploited to develop analgesic regimens that allow lower doses of opioids) Specific anti-migraine drugs Herbal remedies (e.g. cloves, feverfew, kava kava, St John's wort, ginger, ginseng)
 * Panadeine Forte (500mg paracetamol, 30mg codeine)
 * Disprin Forte (500mg aspirn, 9.5mg codeine)
 * Other drugs useful for analgesic effects**

Adjuvant analgesics are medications whose main clinical indications are in other conditions such as anticonvulsants, antidepressants, antihistamines and corticosteroids...