An analgesic (colloquially known as a painkiller) is any member of the diverse group of drugs used to relieve pain (achieve analgesia). Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease Pain, in the sense of physical pain, is a typical sensory experience that may be described as the unpleasant awareness of a noxious stimulus or bodily harm The word analgesic derives from Greek an- ("without") and -algia ("pain"). Analgesic drugs act in various ways on the peripheral and central nervous systems; they include paracetamol (acetaminophen), the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, narcotic drugs such as morphine, synthetic drugs with narcotic properties such as tramadol, and various others. The peripheral nervous system ( PNS) resides or extends outside the Central nervous system (CNS which consists of the Brain and Spinal cord. In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. Paracetamol ( INN) (ˌpærəˈsiːtəmɒl -ˈsɛtə- or acetaminophen ( USAN) is a widely-used Analgesic and Antipyretic Medication Non-steroidal anti-inflammatory drugs, usually abbreviated to NSAID s or NAID s, are drugs with Analgesic, Antipyretic and in higher Salicylic acid (from the Latin word for the willow tree Salix, from whose bark it can be obtained is a Beta hydroxy acid (BHA with the formula The term narcotic (ναρκωτικός is believed to have been coined by the Greek physician Galen to refer to agents that benumb or deaden causing loss Medical uses Morphine can be used as an analgesic in hospital settings to relieve pain in Myocardial infarction pain in Tramadol ( INN) (ˈtræmədɒl is an atypical Opioid which is a centrally acting Analgesic, used for treating moderate to severe Pain.

In choosing analgesia, the severity and response to other medication determines the choice of agent; the WHO "pain ladder", originally developed in cancer-related pain, is widely applied to find suitable drugs in a stepwise manner. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled ^[1] The choice of analgesia is also determined by the type of pain: for neuropathic pain, traditional analgesia is less effective, and there is often benefit from classes of drugs that are not normally considered analgesics, such as tricyclic antidepressants and anticonvulsants. Neuropathy is a medical term usually short for Peripheral neuropathy. Tricyclic antidepressants (abbreviation TCAs) are a class of Antidepressant drugs first used in the 1950s The anticonvulsants, also called antiepileptic drugs (abbreviated "AEDs" are a diverse group of pharmaceuticals used in the treatment of epileptic ^[2]

Contents 1 The major classes 1.1 Paracetamol and NSAIDs 1.2 COX-2 inhibitors 1.3 Opiates and morphinomimetics 1.4 Specific agents 2 Specific forms and uses 2.1 Combinations 2.2 Topical or systemic 2.3 Psychotropic agents 2.4 Atypical and/or adjuvant analgesics 3 Addiction 4 See also 5 References 6 External links

The major classes

Paracetamol and NSAIDs

Main article: Non-steroidal anti-inflammatory drug

The exact mechanism of action of paracetamol/acetaminophen is uncertain, but it appears to be acting centrally. Non-steroidal anti-inflammatory drugs, usually abbreviated to NSAID s or NAID s, are drugs with Analgesic, Antipyretic and in higher Aspirin and the other NSAIDs inhibit cyclooxygenase, leading to a decrease in prostaglandin production; this reduces pain and also inflammation (in contrast to paracetamol and the opioids). Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Non-steroidal anti-inflammatory drugs, usually abbreviated to NSAID s or NAID s, are drugs with Analgesic, Antipyretic and in higher A prostaglandin is any member of a group of Lipid compounds that are derived enzymatically from Fatty acids and have important functions in the Animal body Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens

Paracetamol has few side effects and is regarded as very safe, although excessive doses lead to Analgesic Abuse Nephropathy (AAN) caused by cumulative lifetime use of large amounts (≥ 2 kg) (ref. Nephrotoxicity (from Greek nephros "kidney" is a Poisonous effect of some substances both Toxic chemicals and Medication, on the Kidney Merck Manual) and hepatotoxicity (liver damage). Drug metabolism in liver The human body identifies almost all drugs as foreign substances (i The liver is a vital organ in the human body and is present in Vertebrates and some other animals NSAIDs predispose to peptic ulcers, renal failure, allergic reactions, and occasionally hearing loss, and they can increase the risk of hemorrhage by affecting platelet function. A peptic ulcer, also known as PUD or peptic ulcer disease, is an Ulcer (defined as mucosal erosions equal to or greater than 0 Renal failure or kidney Allergy is a disorder of the Immune system often also referred to as Atopy. Bleeding, technically known as hemorrhaging / haemorrhaging (see American and British spelling differences) is the loss of Blood from Platelets, or Thrombocytes, are small cytoplasmic bodies derived from cells They circulate in the Blood of Mammals and are involved The use of certain NSAIDs in children under 16 suffering from viral illness may contribute to Reye's syndrome. Reye's syndrome is a potentially fatal Disease that causes numerous detrimental effects to many organs especially the Brain and Liver.

COX-2 inhibitors

Main article: COX-2 inhibitor

These drugs have been derived from NSAIDs. COX-2 selective inhibitor is a form of Non-steroidal anti-inflammatory drug (NSAID that directly targets COX-2, an Enzyme responsible for Inflammation The cyclooxygenase enzyme inhibited by NSAIDs was discovered to have at least 2 different versions: COX1 and COX2. Research suggested that most of the adverse effects of NSAIDs were mediated by blocking the COX1 (constitutive) enzyme, with the analgesic effects being mediated by the COX2 (inducible) enzyme. The COX2 inhibitors were thus developed to inhibit only the COX2 enzyme (traditional NSAIDs block both versions in general). These drugs (such as rofecoxib and celecoxib) are equally effective analgesics when compared with NSAIDs, but cause less gastrointestinal hemorrhage in particular. Rofecoxib (Rofecoxib is a nonsteroidal anti-inflammatory drug ( NSAID) marketed by Merck & Co Celecoxib ( INN) (sɛlɨˈkɒksɪb is a Non-steroidal anti-inflammatory drug (NSAID used in the treatment of Osteoarthritis, Rheumatoid arthritis However, post-launch data indicated increased risk of cardiac and cerebrovascular events with these drugs due to an increased likelihood of clotting in the blood due to a decrease in the production of protoglandin around the platelets causing less clotting factor to be released, and rofecoxib was subsequently withdrawn from the market. The role for this class of drug is currently hotly debated. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar.

Opiates and morphinomimetics

Main articles: Opioid and Opiate

Morphine, the archetypal opioid, and various other substances (e. An opioid is a chemical Substance that has a Morphine -like action in the body For other uses see Opiate (disambiguation, or for the class of drugs see Opioid. Medical uses Morphine can be used as an analgesic in hospital settings to relieve pain in Myocardial infarction pain in An opioid is a chemical Substance that has a Morphine -like action in the body g. codeine, oxycodone, hydrocodone, diamorphine, pethidine) all exert a similar influence on the cerebral opioid receptor system. Codeine ( INN) or methylmorphine is an Opiate used for its Analgesic, antitussive and antidiarrheal properties Oxycodone is an Opioid Analgesic Medication synthesized from Thebaine. Hydrocodone or dihydrocodeinone is a semi-synthetic Opioid derived from two of the naturally occurring Opiates Codeine and Thebaine Heroin ( INN: diacetylmorphine, BAN: diamorphine) is a semi-synthetic opioid synthesized from Morphine, a derivative Pethidine ( INN) or meperidine ( USAN) (commonly referred to as Demerol but also referred to as isonipecaine lidol pethanol piridosal Algil Alodan Opioid receptors are a group of G-protein coupled receptors with Opioids as Ligands The Endogenous Opioids are Dynorphins Tramadol and buprenorphine are thought to be partial agonists of the opioid receptors. Tramadol ( INN) (ˈtræmədɒl is an atypical Opioid which is a centrally acting Analgesic, used for treating moderate to severe Pain. Buprenorphine (or colloquially "Bupe" is a semi-synthetic Opiate with partial agonist and antagonist actions An agonist is a term used to describe a type of ligand or drug that binds and alters the activity of a receptor. 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. Myoclonus (maɪˈɒklənəs is brief involuntary twitching of a Muscle or a group of muscles

Opioids, 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). Nausea ( Latin: Nausea, Greek:, " Sea-sickness " also called wamble) is the sensation of unease and discomfort Vomiting (also called throwing up, emesis) is the forceful expulsion of the contents of one's Stomach through the Mouth and sometimes the An anti-emetic is a drug that is effective against Vomiting and Nausea. Pruritus (itching) may require switching to a different opioid. Itch ( Latin: pruritus) is an unpleasant Sensation that evokes the desire or Reflex to scratch Constipation occurs in almost all patients on opioids, and laxatives (lactulose, macrogol-containing or co-danthramer) are typically co-prescribed. Constipation, costiveness, or irregularity, is a condition of the Digestive system in which a person (or animal experiences hard Feces that Laxatives (or purgatives) are foods compounds or drugs taken to induce bowel movements or to loosen the stool most often taken to treat Constipation. Lactulose is a synthetic Sugar used in the treatment of Constipation and Hepatic encephalopathy, a complication of Liver disease. Macrogol is a Laxative. It has been used to treat Constipation.

When used appropriately, opioids and similar narcotic analgesics are otherwise safe and effective, however risks such as addiction and the body becoming used to the drug can occur. The term narcotic (ναρκωτικός is believed to have been coined by the Greek physician Galen to refer to agents that benumb or deaden causing loss Due to the body getting used to the drug often the dose must be increased if it is for a chronic disease this is where the no ceiling limit of the drug comes into play. However what must be remembered is although there is no upper limit there is a still a toxic dose even if the body has become used to lower doses.

Specific agents

In patients with chronic or neuropathic pain, various other substances may have analgesic properties. Tricyclic antidepressants, especially amitriptyline, have been shown to improve pain in what appears to be a central manner. Tricyclic antidepressants (abbreviation TCAs) are a class of Antidepressant drugs first used in the 1950s Amitriptyline (or Amitryptyline) hydrochloride (sold as Elavil Tryptanol Endep Elatrol Tryptizol Trepiline Laroxyl Saroten is a Tricyclic antidepressant The exact mechanism of carbamazepine, gabapentin and pregabalin is similarly unclear, but these anticonvulsants are used to treat neuropathic pain with modest success. Carbamazepine ("CBZ" is an Anticonvulsant and mood stabilizing drug used primarily in the treatment of Epilepsy and Bipolar disorder Gabapentin (brand name Neurontin) is a medication originally developed for the treatment of Epilepsy. Pregabalin ( INN) (prɨˈgæbəlɨn is an Anticonvulsant drug used for Neuropathic pain and as an adjunct therapy for Partial seizures with or The anticonvulsants, also called antiepileptic drugs (abbreviated "AEDs" are a diverse group of pharmaceuticals used in the treatment of epileptic

Specific forms and uses

Combinations

Analgesics are frequently used in combination, such as the paracetamol and codeine preparations found in many non-prescription pain relievers. Codeine ( INN) or methylmorphine is an Opiate used for its Analgesic, antitussive and antidiarrheal properties They can also be found in combination with vasoconstrictor drugs such as pseudoephedrine for sinus-related preparations, or with antihistamine drugs for allergy sufferers. Pseudoephedrine (commonly abbreviated as PSE is a sympathomimetic Amine commonly used as a Decongestant. Paranasal sinuses are air-filled spaces communicating with the nasal cavity within the bones of the Skull and face A histamine antagonist is an agent which serves to inhibit the release or action of Histamine.

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 combatting 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. Ibuprofen ( INN) (ˌaɪbjuːˈpɹəʊfɛn (from the now outdated nomenclature i so- bu tyl- pro panoic- phen olic acid is a Non-steroidal Naproxen ( INN) (nəˈprɒksən is a Non-steroidal anti-inflammatory drug (NSAID commonly used for the reduction of moderate to severe Pain, Fever Non-steroidal anti-inflammatory drugs, usually abbreviated to NSAID s or NAID s, are drugs with Analgesic, Antipyretic and in higher ^[3]

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. Ibuprofen ( INN) (ˌaɪbjuːˈpɹəʊfɛn (from the now outdated nomenclature i so- bu tyl- pro panoic- phen olic acid is a Non-steroidal Diclofenac (marketed as Flector patch, Voltaren, Voltarol, Diclon, Dicloflex Difen, Difene, Cataflam Capsaicin /ˌkæpˈseˌɪsɪn/ (8- Methyl - N - Vanillyl -6-nonen Amide) is the active component of Chili peppers Lidocaine, an anesthetic, and steroids may be injected into painful joints for longer-term pain relief. Lidocaine ( INN) (ˈlaɪdoʊkeɪn or lignocaine (former BAN) (/ˈlɪgnoʊkeɪn/ is a common Local anesthetic and antiarrhythmic drug Anesthesia, or anaesthesia (see spelling differences; from Greek grc αν- an-, "without" and grc αἲσθησις Glucocorticoids (GC are a class of Steroid hormones characterised by an ability to bind with the glucocorticoid receptor ( GR) and trigger similar effects Lidocaine is also used for painful mouth sores and to numb areas for dental work and minor medical procedures. Lidocaine ( INN) (ˈlaɪdoʊkeɪn or lignocaine (former BAN) (/ˈlɪgnoʊkeɪn/ is a common Local anesthetic and antiarrhythmic drug An oral ulcer (from Latin ulcus) is the name for the appearance of an open sore inside the mouth caused by a break in the Mucous membrane or the epithelium Dentistry' is the "evaluation diagnosis prevention and/or treatment (nonsurgical surgical or related procedures of diseases disorders and/or conditions of the oral cavity

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. Cannabinoids ( are a group of terpeno[[phenol]]ic compounds present in Cannabis ( Cannabis sativa L Cannabis sativa is an annual plant in the Cannabaceae family It is a Herb that has been used throughout recorded history by humans for various purposes Other psychotropic analgesic agents include ketamine (an NMDA receptor antagonist), clonidine and other α₂-adrenoreceptor agonists, and mexiletine and other local anaesthetic analogues. Ketamine is a drug for use in human and veterinary medicine developed by Parke-Davis (today a part of Pfizer) in 1962 Clonidine is a direct-acting α2 Adrenergic agonist prescribed historically as an Antihypertensive agent Mexiletine ( INN, sold under the trade name Mexitil) belongs to the Class IB anti-arrhythmic group of medicines

Atypical and/or adjuvant analgesics

Orphenadrine, cyclobenzaprine, scopolamine, atropine, gabapentin, first-generation antidepressants and other drugs possessing anticholinergic and/or antispasmodic properties are used in many cases along with analgesics to potentiate centrally acting analgesics such as opioids when used against pain especially of neuropathic origin and to modulate the effects of many other types of analgesics by action in the parasympathetic nervous system. Orphenadrine (sold under the Brand names Norflex Mephenamin Disipal Banflex Flexon Biorphen Brocasipal and others is an Anticholinergic Drug of Cyclobenzaprine is a long-acting skeletal muscle relaxant. It is marketed as Flexeril (5 and 10 mg tablets and also as Fexmid (7 The fictional truth drug Hyoscine-pentothal does not describe real hyoscine accurately Atropine is a Tropane Alkaloid extracted from Deadly nightshade ( Atropa belladonna) Jimsonweed (Datura stramonium and other plants Gabapentin (brand name Neurontin) is a medication originally developed for the treatment of Epilepsy. An antidepressant is a Psychiatric medication used for alleviating major depression or Dysthymia ('milder' depression An anticholinergic agent is a substance that blocks the Neurotransmitter acetylcholine in the central and the Peripheral nervous system. An antispasmodic (synonym spasmolytic) is a drug or an herb that suppresses Spasms These are usually caused by smooth Muscle contraction especially An opioid is a chemical Substance that has a Morphine -like action in the body The parasympathetic Nervous system ( PSNS) is a division of the Autonomic nervous system (ANS along with the Sympathetic nervous system Dextromethorphan has been noted to slow the development of tolerance to opioids and exert additional analgesia by acting upon the NMDA receptors; some analgesics such as methadone and ketobemidone and perhaps piritramide have intrinsic NMDA action. Dextromethorphan ( DXM or DM) is an Antitussive (cough suppressant drug found in many over-the-counter cold and Cough medicines NMDA (N-methyl-D-aspartic acid is an Amino acid derivative acting as a specific Agonist at the NMDA receptor, and therefore mimics the action of the Methadone ( Dolophine Amidone Methadose Physeptone Heptadon and many others is a synthetic Opioid, used medically as an Analgesic, Antitussive Ketobemidone (Cliradon Ketogan Ketodur Cymidon Ketorax &c is a powerful Opioid Analgesic. Piritramide ( Dipidolor, Piridolan, Pirium and others is a synthetic Opioid Analgesic with a potency 0 Strong liquor has been used in the past as an agent for dulling pain, due to the CNS depressant effects of ethyl alcohol, most notably during the Civil War. A civil war is a War between a State and domestic political actors that are in control of some part of the territory claimed by the state However, the ability of alcohol to "kill pain" is obviously inferior to virtually all of analgesics used today (e. g. morphine, codeine). As such, the idea of alcohol for analgesia is generally reguarded as being as primitive as the practice in virtually all industrialized countries today.

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, antihistamines 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 histamine antagonist is an agent which serves to inhibit the release or action of Histamine. Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic Ephedrine (EPH is a Sympathomimetic Amine commonly used as a Stimulant, appetite suppressant concentration aid Decongestant, and to treat Dextroamphetamine is a Psychostimulant which produces increased wakefulness energy and self-confidence in association with decreased fatigue and appetite Cocaine ( benzoylmethyl ecgonine) is a Crystalline Tropane Alkaloid that is obtained from the leaves of the Coca plant A well-accepted benefit of THC to chronic pain patients on opioids is its superior anti-nauseant action. Some think it would make more sense to use the synthetic THC capsule (trade name Marinol), which is administered orally. However, in patients suffering from nausea, the swallowing of the capsule itself may provoke vomiting. Likewise, the use of medicinal cannabis remains a debated issue. Cannabis ( Cán-na-bis) is a Genus of Flowering plants that includes three putative species Cannabis sativa subsp

Addiction

In the United States in recent years, there has been a wave of new addictions to prescription narcotics such as oxycodone (such as OxyContin, or with acetaminophen, as Percocet) and hydrocodone (commonly prescribed with acetaminophen, as in Vicodin, Lortab etc. The United States of America —commonly referred to as the The term " addiction " is used in many contexts to describe an obsession compulsion or excessive Physical dependence or psychological dependence such as Oxycodone is an Opioid Analgesic Medication synthesized from Thebaine. Oxycodone is an Opioid Analgesic Medication synthesized from Thebaine. Paracetamol ( INN) (ˌpærəˈsiːtəmɒl -ˈsɛtə- or acetaminophen ( USAN) is a widely-used Analgesic and Antipyretic Medication Oxycodone is an Opioid Analgesic Medication synthesized from Thebaine. Hydrocodone or dihydrocodeinone is a semi-synthetic Opioid derived from two of the naturally occurring Opiates Codeine and Thebaine Vicodin EC is a Trademarked Brand of Narcotic Analgesics (painkillers containing Hydrocodone and Paracetamol ( Acetaminophen ) when available in pure formulations as opposed to combined with other medications (as in Percocet which contains both oxycodone and acetaminophen/paracetamol). Oxycodone is an Opioid Analgesic Medication synthesized from Thebaine.

See also

• Pain management
• Patient-controlled analgesia
• Co-proxamol

References

External links

• Bandolier pain site (Oxford pain group)

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