What are the current “pharmaceutical” products/systems for pain management?

Pain management (also called pain medicine) is the discipline concerned with the relief of pain.

Acute pain, such as occurs with trauma, often has a reversible cause and may require only transient measures and correction of the underlying problem. In contrast, Chronic pain often results from conditions that are difficult to diagnose and treat, and that may take a long time to reverse. Some examples include cancer, neuropathy and referred pain. Often, pain pathways are set up that continue to transmit the sensation of pain even though the underlying condition or injury that originally caused pain has been healed. In such situations, the pain itself is frequently managed separately from the underlying condition of which it is a symptom, or the goal of treatment is to manage the pain with no treatment of any underlying condition (e.g. if the underlying condition has resolved or if no identifiable source of the pain can be found).

Pain management generally benefits from a multidisciplinary approach that includes pharmacologic measures (analgesics such as narcotics or NSAIDs and pain modifiers such as tricyclic antidepressants or anticonvulsants), non-pharmacologic measures (such as interventional procedures, physical therapy and physical exercise, application of ice and/or heat), and psychological measures (such as biofeedback and cognitive therapy).

Pain management practitioners come from all fields of medicine. Most often, pain fellowship trained physicians are anesthesiologists, neurologists, physiatrists or psychiatrists. Some practitioners focus more on the pharmacologic management of the patient, while others are very proficient at the interventional management of pain. Interventional procedures - typically used for chronic back pain - include: epidural steroid injections, facet joint injections, neurolytic blocks, Spinal Chord Stimulators and intrathecal drug delivery system implants, etc. Over the last several years the number of interventional procedures done for pain has grown to a very large number.

As well as medical practitioners, the area of pain management may often benefit from the input of Physiotherapists, Chiropractors, Clinical Psychologists and Occupational Therapists, amongst others. Together the multidisciplinary team can help create a package of care suitable to the patient. One of the pain management modalities are trigger point injections and nerve blocks utilizing long acting anesthetics and small doses of steroids.

Analgesia
An analgesic (colloquially known as a painkiller) is any member of the diverse group of drugs used to alleviate pain (achieve analgesia). The word analgesic derives from Greek an- ("without") and -algia ("pain"). 
Analgesic drugs act in various ways on the peripheral and central nervous systems. 

The major classes 

They include:

  1. paracetamol (acetaminophen),
  2. the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates,
  3. narcotic drugs such as morphine, 
  4. synthetic drugs with narcotic properties such as tramadol, 
  5. and various others. 

Paracetamol
Paracetamol is a p-aminophenol derivative that exhibits analgesic and antipyretic activity. It does not possess anti-inflammatory activity.

Paracetamol is thought to produce analgesia through a central inhibition of prostaglandin synthesis. aracetamol is metabolised extensively in the liver and excreted in the urine mainly as inactive glucuronide and sulfate conjugates. Less than 5% is excreted unchanged. The metabolites of paracetamol include a minor hydroxylated intermediate which has hepatotoxic activity. This intermediate metabolite is detoxified by conjugation with glutathione, however, it can accumulate following paracetamol overdosage (more than 150mg/kg or 10g total paracetamol ingested) and if left untreated can cause irreversible liver damage, often heightened with use of alcohol. The number of accidental self-poisonings and suicides has grown in recent years.

Aspirin
Aspirin (acetylsalicylic acid) is an anti-inflammatory pain killer (NSAID), which is extensively used, worldwide, for pain relief, to reduce inflammation and temperatures, and to reduce the risk of heart attacks and strokes. Aspirin works to reduce inflammation and pain, by inhibiting cyclooxygenase, leading to a decrease in prostaglandin production; this reduces pain and also inflammation (in contrast to paracetamol and the opioids).

The most common unwanted affect is indigestion, and so it should not be used (except on medical advice) in someone who has a peptic ulcer or has had one in the past.  Also as a result of this side effect, it should be used with caution, if at all, in somebody prone to heartburn or indigestion. It is best to take aspirin after food. Skin rashes occur in some people, and sometimes with dramatic swelling of the face and mouth and difficulty breathing (anaphyllactic reaction). 
A very rare, but serious condition in children (Reye's Syndrome) is believed to be more likely to happen in children who have taken aspirin for mild viral symptoms. As a result, aspirin is no longer used routinely in children below the age of 16 years or for breast feeding mothers.

NSAIDs
NSAIDs (like Aspirin) inhibit cyclooxygenase, leading to a decrease in prostaglandin production; this reduces pain and also inflammation (in contrast to paracetamol and the opioids).  NSAIDs may predispose to peptic ulcers, renal failure, allergic reactions and hearing loss. They may also increase the risk of hemorrhage by affecting platelet function. The use of certain NSAIDs in children under 16 suffering from viral illness may contribute to Reye’s Syndrome.

Opiates and morphinomimetics
Morphine,the archetypal opioid, and various other substances (e.g. Codeine, Pethidine, etc.) all exert a similar influence on the cerebral opioid receptor system. Dosing of all opioids may be limited by opioid toxicity (confusion, respiratory depression, myoclonic jerks and pinpoint pupils), but there is no dose ceiling in patients who tolerate this. pioids, while very effective analgesics, may have some unpleasant side-effects. Up to 1 in 3 patients starting morphine may experience nausea and vomiting (generally relieved by a short course of antiemetics). Pruritus (itching) may require switching to a different opioid. Constipation occurs in almost all patients on opioids, and laxatives are typically co-prescribed.  Whn used appropriately, opioids and similar narcotic analgesics are otherwise safe and effective, carrying relatively little risk of addiction. Occasionally, gradual tapering of the dose is required to avoid withdrawal symptoms.

Psychotropic agents
Tetrahydrocannabinol THC) and some other cannabinoids, either from the Cannabis sativa plant or synthetic, have analgesic properties, although the use of cannabis derivatives is illegal in many countries. Other psychotropic analgesic agents include ketamine (an NMDA receptor antagonist), clonidine and other α2-adrenoreceptor agonists, and mexiletine and other local anaesthetic analogues.

Adjuvant analgesics
The use of adjuvant analgesics is an important and growing part of the pain-control field and new discoveries are made practically every year. Many of these drugs combat the side effects of opioid analgesics, an added bonus. For example, antihistimines including orphenadrine combat the release of histamine caused by many opioids, methylphenidate, caffeine, ephedrine, dextroamphetamine and cocaine work against heavy sedation and may elevate mood in distressed patients as do the antidepressants. A well-accepted benefit of THC to chronic pain patients on opioids is its superior anti-nauseant action. However, it would make more sense to use the Marinol capsule, or oral, rectal, or vapour administration of hash oil, rather than smoking cannabis, for the same reasons most doctors advise against smoking tobacco, even though it is more easily obtained.

Combinations
Analgesics are frequently used in combination, such as the paracetamol and codeine preparations found in many non-prescription pain relievers. They can also be found in combination with vasoconstrictor drugs such as pseudoephedrine for sinus-related preparations, or with antihistimine drugs for allergy sufferers.

The use of paracetamol, as well as aspirin, ibuprofen, naproxen, and other NSAIDs concurrently with weak to mid-range opiates (up to about the hydrocodone level) has been shown to have beneficial synergistic effects by combating pain at multiple sites of action—NSAIDs reduce inflammation which, in some cases, is the cause of the pain itself while opiates dull the perception of pain—thus, in cases of mild to moderate pain caused in part by inflammation, it is generally recommended that the two be prescribed together.

Topical or systemic
Topical analgesia is generally recommended to avoid systemic side-effects. 
Painful joints, for example, may be treated with an ibuprofen- or diclofenac-containing gel; capsaicin also is used topically. Lignocaine, Tetracaine, Prilocaine and Benzocaine, (topical anesthetics), and steroids may be injected into painful joints for longer-term pain relief. Topical anesthetics are also used for painful mouth sores and to numb areas for dental work and minor medical procedures.

Addiction
In recent years, there has been a wave of new addictions to prescription narcotics such as oxycodone (or with acetaminophen) and hydrocodone (commonly prescribed with acetaminophen) when available in pure formulations as opposed to combined with other medications (as in products which contains both oxycodone and acetaminophen/paracetamol). Hydrocodone is only available in pure form in some European countries as the original hydrocodone pharmaceutical, Dicodid tablets. Far from reducing addiction liability, the paracetamol content of many codeine, dihydrocodeine, hydrocodone, and oxycodone pharmaceuticals in the United States only saddles users with the high risk of severe liver damage, and extraction of the opioids with cold water or solvents reduces this problem for the sophisticated abuser, self-medicator, and legitimate prescription holder alike.

In all of the above information, obtained from sites such as medical journals and even the TGA website, two things stand out;

1. All of the analgesics recommended (and sold OTC) do not work on the cause of the pain itself – only the sensation of pain. You may still be suffering from an acute or chronic problem but not feel any effects due to high analgesic dosages. 
This may be counterproductive and why is there a standard regulatory instruction “If the pain persists seek medical advice”?

2. There is no mention of Aromatherapy, which has been used in areas such as pain management for the last few thousand years.

Why?

Excerpt from Pain Management using Essential Oils and Aromatherapy Validated by Digital Infrared Thermal Imaging Technology - Presented to The 42nd Conference of the Australian Society of Cosmetic Chemists.

Cheryl Gilbert 
Owner/CEO, Balanced Essentials Pty Ltd., 
Glenorie, NSW

Pauline Rose RN, 
Thermographer. Complementary & Ecological Medicine, 
Crows Nest, Sydney

Ric Williams (B.Sc.; Dip.Env.St.)
Research & Development Manager
Cosmepeutics International