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Pain Relief Medications (Analgesics) Overview
What are pain medications (analgesics)
Pain is the oldest complaint that medicine has attempted to treat, and there are thousands of different ways to reduce pain with chemicals. Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. Pain medications (also called analgesics or pain relievers) are a class of drugs used to relieve pain. Analgesics lessen the amount, duration, or sensation of pain. They work by reducing the amount of pain felt and this is generally achieved by interfering with the way the pain message is transmitted by the nerves. Analgesics do not treat the problem causing the pain, but they provide temporary relief from pain symptoms. Analgesics are used to treat pain related to many conditions, including the following:
Analgesics work at the level of the nerves, either by blocking the signal from the peripheral nervous system, or by distorting the interpretation by the central nervous system. Selection of an appropriate analgesic is based on consideration of the risk-benefit factors of each class of drugs, based on type of pain, severity of pain, and risk of adverse effects. Each pain medication has its advantages and risks. Specific types of pain may respond better to one kind of medication than to another kind. Each person may have a slightly different response to a pain medication. How long pain medications stay in
your system
How long a pain medication stays in your system depends on the type and dosage of medication and your body weight. Types of pain medications range from the more gentle over-the-counter drugs (i.e. acetaminophen) to the very strong and highly addictive opioids (i.e. codeine and morphine). Also, a higher dosage of medication will stay in your system longer than a lower dosage. In addition, a painkiller will stay in the system of a lightweight person longer than the same dose in a heavier person. Types of pain medications
There are three basic categories of analgesics:
Pain medications within these classes function differently. Some are more useful than the others, depending on the person and the type of pain. Many pain-killing medications have side effects ranging from relatively mild stomach irritation to severe addiction. There are many different types of medications used to treat pain, including those available over-the-counter (OTC) without a doctor's prescription and those obtained only by a doctor's prescription. Non-narcotic (non-opioid) analgesics
Acetaminophen
Acetaminophen (Tylenol) is a pain reliever and fever reducer with no anti-inflammatory properties. It relieves pain by working centrally (in the brain) to elevate the pain threshold and thus switching off the perception of pain. It is appropriate for mild to moderate pain. Acetaminophen has very few side effects and is relatively inexpensive. It is less irritating to the stomach than other over-the-counter pain medications and is safer for children. However, the risk of liver or kidney damage is significant when more than the recommended dose of acetaminophen is used. Advantages: there is no chance of addiction, patients do not develop a tolerance (loss of pain relieving effect) with extended use, acetaminophen does not produce gastrointestinal (stomach) upset, very few patients are allergic to this medication. Because acetaminophen is largely free of side effects at therapeutic doses, it has been considered the first choice for mild pain, including that of osteoarthritis. Non-steroidal anti-inflammatory drugs (NSAIDs)
Non-steroidal anti-inflammatory drugs (NSAIDs) represent a widely used group of drugs. Drugs in this class have varying degrees of anti-inflammatory, antipyretic, and analgesic properties as well as different side effects, time to onset of action, and duration of action. Non-steroidal anti-inflammatory drugs are drugs with analgesic, antipyretic and anti-inflammatory effects. These drugs stop cyclooxygenase enzymes (also called COX enzymes) in the body from working. COX enzymes speed up the body's production of hormone-like substances called prostaglandins. Prostaglandins cause the feeling of pain by irritating the nerve endings. They are also part of the system that helps the body control its temperature. By inhibiting COX enzymes and as a consequence by reducing the level of prostaglandins, NSAIDs help relieve pain. They also help reduce inflammation (swelling), lower fevers and prevent blood from clotting. NSAIDs are used primarily to treat inflammation, mild to moderate pain, and fever. Specific uses include the treatment of headaches, arthritis, sports injuries, and menstrual cramps. Aspirin (also an NSAID) is used to inhibit the clotting of blood and prevent strokes and heart attacks in individuals at high risk. NSAIDs are used to relieve pain related to the following conditions:
Like acetaminophen, they are relatively inexpensive. However, NSAIDs are usually not appropriate for people with stomach problems because they may have a higher risk for stomach bleeding. All NSAIDs except aspirin increase the risk of serious adverse cardiovascular events, such as heart attack or stroke. These drugs may also interfere with other medications or cause serious side effects. Common side effects of NSAIDs include: upset stomach, nausea, abdominal pain, diarrhea, heartburn, unusual bleeding, drowsiness, dizziness, skin rashes. More severe side effects of NSAIDs include: allergic reactions, high blood pressure, stomach bleeding, stomach ulcers (with long-term use), kidney or liver problems.
NSAID medications include: Fenoprofen (Nalfon), Ibuprofen (Motrin), Flurbiprofen (Ansaid), Ketoprofen (Oruvail), Naproxen (Naprosyn), Oxaprozin (Daypro), Diclofenac sodium (Voltaren), Diclofenac potassium (Cataflam), Etodolac (Lodine), Indomethacin (Indocin), Ketorolac (Toradol), Sulindac (Clinoril), Tolmetin (Tolectin), Meclofenamate (Meclomen), Nabumetone (Relafen), Piroxicam (Feldene) and others. Most NSAIDs are appropriate only for oral administration; however ketorolac (Toradol) is appropriate for injection and may be used in moderate to severe pain for short periods. Ketorolac is approved for the short-term management of moderately severe postoperative acute pain. Ketorolac has the distinction of being the only non-narcotic analgesic available in a parenteral formulation that can be administered for the relief of acute pain. COX-2 inhibitors
COX-2 inhibitors are a relatively new type of prescription nonsteroidal anti-inflammatory drugs that reduces pain and inflammation by blocking a specific enzyme (COX-2) in the body. These medications target only the COX-2 enzyme that stimulates the inflammatory response. Because they do not block the actions of the COX-1 enzyme, these medications generally don't cause the kind of stomach upset or bleeding that traditional NSAIDs do. COX-2 inhibitors also don't offer the same kind of protection against heart disease. Currently, only celecoxib (Celebrex) remains on the market. Valdecoxib (Bextra) and rofecoxib (Vioxx) have been voluntarily withdrawn from the market by their manufacturers because of an increased risk of heart attack, stroke, and severe skin toxicity. Conditions treated with COX-2 inhibitors include osteoarthritis, rheumatoid arthritis and some types of acute pain. These drugs are often more expensive than other NSAIDs. Narcotic (opioid) analgesics
Opioids are narcotic pain medications that contain natural, synthetic or semi-synthetic opiates (natural opium alkaloids). Opioid analgesics, act directly on the central nervous system. Opioids have a higher analgesic potency and wider range of indications than any of the other currently available medications for pain control. They are used to relieve severe pain and are often prescribed to patients recovering from operations and serious injuries. Opioid analgesics differ in their potency, speed of onset, duration of action, and route of administration. Commonly used narcotics, listed in ascending order of potency (strength) include: codeine (Tylenol #3), propoxyphene (Darvocet), hydrocodone (Vicodin), oxycodone (Percocet, Oxycontin). The most potent opioids are fentanyl (Sublimaze), hydromorphone (Dilaudid), meperidine (Demerol), morphine, oxymorphone (Numorphan). Opioids act by attaching to specific proteins called opioid receptors, which are found in the brain, spinal cord, and gastrointestinal tract. When these compounds attach to certain opioid receptors in the brain and spinal cord, they can effectively change the way a person experiences pain. They inhibit pain-transmitting neurons and stimulate pain-inhibitory neurons thus changing the brain’s interpretation of pain. Long-term use of narcotic analgesics can lead to physical dependence - the body adapts to the presence of the substance and withdrawal symptoms occur if use is reduced abruptly. This can also include tolerance, which means that higher doses of a medication must be taken to obtain the same initial effects. Physical dependence is not the same as addiction. Physical dependence can occur even with appropriate long-term use of opioid and other medications. Addiction is a compulsive, often uncontrollable drug use in spite of negative consequences. Narcotic pain medications have several side effects and potential risks, such as impairment of mental function, drowsiness, dizziness, constipation, nausea, vomiting, dry mouth, sedation. Patients taking a narcotic should avoid driving or operating heavy machinery. Addiction to narcotics is a possible, but unlikely, event. It is rare for people to become addicted to opioids if the drugs are used to treat pain for a short period of time. Studies have shown that properly managed medical use of opioid analgesics is safe and rarely causes addiction. Taken exactly as prescribed, opioids can be used to manage pain effectively. Opioids do not cause bleeding in the stomach or other parts of the body as can other types of pain relievers. Despite significant side effects, opioid analgesics remain the most potent and widely used pain-relieving drugs. Narcotic analgesics are used in moderate to severe types of pain. Opioids are the most effective pain relievers available to patients today. Tramadol (Ultram)
Tramadol HCl, marketed as Ultram in the USA, was introduced as a non-scheduled drug in April 1995 based on the assumption that the risk of abuse was sufficiently low to warrant a non-scheduled status. Tramadol is an effective pain reliever. It acts centrally (in the brain) to modulate the sensation of pain and has no anti-inflammatory effect. Its mode of action resembles that of narcotics, but it has significantly less potential for abuse and addiction than the narcotic pain medications. Tramadol is as effective as narcotics in relieving pain but does not depress respiration, a side effect of most narcotics. Tramadol has properties similar to antidepressants as it affects neurotransmitters (like an antidepressants). Tramadol is prescribed to treat moderate-to-severe acute pain. Tramadol is often a good option for treatment of pain because patients do not build up a tolerance with extended usage and there is a very low incidence of addiction. Clinically effective analgesic doses of tramadol were comparable to those of pethidine (meperidine) and about 10 times higher than those of morphine. Tramadol has been successful in the treatment of postoperative pain. Comparative studies have generally shown that tramadol is more effective than NSAIDs for controlling postoperative pain. Tramadol is not well tolerated by everyone, and some people report feeling "weird" or "unusual" while on the medication. Common adverse effects of tramadol include dizziness, nausea, dry mouth, and sedation. Tramadol does not have the increased risk of stomach ulceration and internal bleeding that can occur with the use of NSAIDs. The abuse potential seems low. The recommended oral dosage is 50-100 mg every four to six hours. Combined analgesics
Compound or combined analgesics usually contain a small amount of a mild opioid, and a simple analgesic such as aspirin or paracetamol, all within one tablet or capsule. These combination analgesics are often prescribed if the non-opioid painkillers are not enough. People who experience migraines may use combination analgesics. Some combination analgesics are: Aspirin with codeine, Dextropropoxyphene with paracetamol, Dihydrocodeine with paracetamol, Paracetamol with codeine. Adjuvant analgesics
Adjuvant analgesics are drugs that are used primarily for treating conditions other than pain. The adjuvant analgesics are not analgesics in the true pharmacological sense, but may contribute significantly to pain relief in selected circumstances when used either alone or in combination with other analgesics. Adjuvant analgesics comprise a various group of medications with different primary indications and include antidepressants (such as triclyclic antidepressants (TCAs), antiepileptic drugs, muscle relaxants. Antidepressants
Antidepressants have been used for decades as primary analgesics. They may be considered multipurpose analgesics, appropriate for a trial in any persistent pain condition. Analgesic effect occurs at lower doses and more quickly than antidepressant effects. The tricyclic antidepressants have been well studied and are most likely to be effective. Tricyclic antidepressants (TCAs) such as amitriptyline, nortriptyline and desipramine have demonstrated efficacy for migraine, diabetic peripheral neuropathy, post-herpetic neuralgia (PHN), arthritis pain and post-stroke pain. The most evidence exists for amitriptyline but some patients cannot tolerate its sedating, anticholinergic, and appetite-stimulating effects. Desipramine or nortriptyline may be better tolerated in such cases. Controlled studies of the tricyclic antidepressants (TCAs) have shown that the usually effective analgesic dose is often lower than that required to treat depression, and the onset of analgesic action usually is earlier. TCAs are probably more effective at relieving neuropathic pain than the newer antidepressants, but have double the rate of adverse effects. Tricyclic antidepressants side effect liability is higher than newer drugs. Unfortunately, newer serotonin-selective reuptake inhibitors lack efficacy in pain relief. Paroxetine (Paxil) is the only SSRI that has some evidence for efficacy in treating chronic pain. There has recently been some published evidence for the effectiveness of Venlafaxine (Effexor) and Bupropion (Wellbutrin) for neuropathic pain. The selective serotonin and norepinephrine reuptake inhibitors (SNRIs) appear to be more effective analgesics than the selective serotonin reuptake inhibitors. Two SNRIs venlafaxine (Effexor) and duloxetine (Cymbalta) have been shown to be analgesic in several studies. Venlafaxine (Effexor) provides inconsistent effects while duloxetine (Cymbalta), the newest of the SNRIs has been the first antidepressant approved by the FDA as a treatment for pain due to diabetic neuropathy. Drugs that are predominantly noradrenergic, such as bupropion, also may be analgesic. Bupropion inhibits neuronal norepinephrine and serotonin uptake and, less potently, dopamine reuptake. The drug is commonly used for smoking cessation therapy as well as depression. It can be activating and therefore useful in patients with hypoactive depression, fatigue, or sedation. Bupropion is associated with a low risk for somnolence or sexual dysfunction, which is common with other antidepressants. Anticonvulsants (Anti-epileptic
drugs)
Anticonvulsants are commonly used to manage and treat neuropathic pain. Although these drugs have been used for decades, their widespread use for pain did not begin until several years after the FDA approval of gabapentin (Neurontin). Gabapentin (Neurontin) is currently the most commonly prescribed drug for this indication. It is FDA approved for the treatment of diabetic painful polyneuropathy and postherpetic neuralgia. Pregabalin, which is a distinct compound but has the same mechanism of action, was recently approved for the same indications. This drug has more stable pharmacokinetics than gabapentin and should be simpler to use. Other antiepileptics, such as phenytoin, carbamazepine, clonazepam and valproic acid, and newer drugs, such as lamotrigine, topiramate, tiagabine, and oxcarbazepine, also are used as analgesics for neuropathic pain. Anticonvulsants are given at similar doses as for seizure management. Skeletal muscle relaxants
Skeletal muscle relaxants (cyclobenzaprine, carisoprodol) relieve pain from muscle spasms by promoting muscle relaxation and depressing the nervous system, and many of them are variations of tricyclic antidepressants and benzodiazepines like Valium or Librium. Local anesthetics/antiarrythmics
Local anesthetics may provide relief of neuropathic pain if neither antidepressants or anticonvulsants are effective. Topical 5% lidocaine gel (Lidoderm) has modest effectiveness in post herpetic neuralgia. No systemic side effects. |