Pharmacotherapy ,or drug treatment is without a doubt, one of the fundamentals of pain therapy. At the same time, it's important to note that the type, dose, and the duration of action of a chosen pharmacological treatment will vary considerably according to the type, cause, and duration of the pain treated. It will also be influenced by additional factors like the patient's general health condition, other treatments, et cetera. Before getting into the basic principles of a Pharmacotherapy, I like to mention that there are dozens of painkillers that not all drugs are available in all countries, and their brand names often vary from one country to the next. Nonetheless, I'd like to start by categorizing the pain killer arsenal of commonly use analgesic drugs into six classes. The first class is that of simple analgesics. They typically consist of acetominophen, also called paracetamol. They are considered weak analgesic and are used alone for mild pain or in combination with other classes for moderate to severe pain. According to medic guidelines, acetominophen is considered a first line of treatment for osteoarthritis that can be used for other conditions as well. The second class is that of non-steroidal anti-inflammatory drugs, known as NSAID. They reduce inflammation, and therefore reduce inflammatory pain. They inhibit an enzyme called cyclooxygenase, known as COX, which produces prostaglandins, strong moderators of inflammation. Principally, there are two types of COX enzymes, one and two. While type two is mainly in used during inflammation, type one has important roles, such as protecting the stomach membrane, kidney function, and blood clotting. Accordingly, the NSAIDs are subdivided into two categories, non-selective NSAIDs, which block the two COX enzymes simultaneously. Ibuprofen, naproxen, and diclofena, are typical examples of these category. And the COX two selective drugs block mainly the COX two enzyme, including etericoxib and celecoxib. In the past, only non-selective NSAIDs existed but cause gastric ulcers, which led in many patients to significant complications. The advantage of the newer COX two selective drugs is reduced prevalence of some of these gastric problems. In contrast, after the introduction of the COX two selective drugs, reports on thromboembolic, such as heart attacks and stroke, emerged. These were initially thought to be related only to the COX two selective drugs, but it is now recognized that almost all NSAIDs, regardless of their selectivity, increase the risk for thromboembolic effect. This led the FDA and the corresponding European agency, EMA to release clear warnings that all such drugs should be used at the lowest possible dose and for the shortest conceivable period of time. They can still be safely used for acute pain and for acute relapse of chronic pain. NSAIDs is a very effective for inflammatory pain with no marked difference between the selective and non-selective classes. The third group is that of opioid analgesics, which are a cornerstone in the treatment of moderate to severe pain. There is a wide consensus regarding the effectiveness and appropriateness of the use for acute and cancer-related pain. However, there are growing concerns, mainly in North America, about the prescriptions for long term treatment of chronic pain. There are several reasons for these concerns. First, clear evidence regarding their effectiveness in patients with chronic pain is limited to several months at most. Second, there is increase for abuse and addiction with long term opioid use. Third, report from North America indicate that chronic opioid abuse may be associated with unexpected epidemic of mortalities. Interestingly, recent European reports do not concur with a North American observation. It should be noted that the US population accounts for five percent of the world population but consumes more than 50 percent of the world's medical opioids. From the clinical standpoint, there are different opioid compounds, which are traditionally subdivided into weak and strong opioids. Examples for weak opioids, which are also called opioids for moderate pain are codeine and tramadol. Among the strong opioids or opioids for strong pain, we find morphine, oxycodone, and fentanyl. Finally, aside from the raised concerns regarding addiction and fatalities, opioids may have other adverse effects, including constipation, nausea, sedation, and unsteadiness. The next class of medication is that of adjuvant drugs. These are drugs for the treatment of medical issues not related to pain but have been found helpful in the alleviation of certain pain conditions. The two main examples for drugs in this class are the antidepressants and anticonvulsants. These drugs can reduce neuropathic pain and are also found effective in headache prophylactics. There are three main sub-classes of antidepressants including tricyclic antidepressants, known as TCA, with amitriptyline as a hallmark agent. There are the serotonin and nor-epinephrine reuptake inhibitors, known as SNRI, with duloxetine as an example. And there are also the selective serotonin reuptake inhibitors, known as SSRIs with the Prozac as a prototype. Two important notes about antidepressants. First, the most effective sub-classes of antidepressants are the TCAs and the SNRIs. Second, these drugs produce analgesia independently of their effect on depression. There are so many types of anti-convulsants. But the most commonly used in the context of pain control are the gabapentinoids, pregabalin, and gabapentin. Carbamazepine, known as Tegretol in many parts of the world, is used mainly for a very specific type of neuropathic pain in the face called trigeminal neuralgia. All of these adjuvant drugs have side effects like drowsiness, sedation, constipation, and sexual dysfunction. In many patients, those side effects are transient and will resolve either spontaneously or soon after the end of their use. Local anesthetics, our next class of medications, are used very often from the management of acute pain during an act of surgery via nerve or epidural blocks. Some pain clinics use intravenous infusions of local anesthetics for neuropathic pain or intractable migraine. The main problem with local anesthetics, either a short duration of action, which lasts several hours at most. The last class of drugs fall into a category of heterogeneous drugs for different specific conditions. One specific drug is used for headache pain, mainly migraine. The most famous class is that of triptans, which are quite potent in aborting migraine attacks. It can be used orally, via nasal spray, or self-injection. There are other drugs which don't fall into any of the above categories, but they're still commonly used in pain medicine, such as the drugs which relieve muscle spasm. Now that you are a little more familiar with the different drug classes, we'll reveal some of the principles of drug use. First, an attempt should always be made to make a precise diagnoses for the type of pain needs to be treated. Is it neuropathic pain? Is it inflammatory pain, headache or any other type of pain? Second, the context of the pain should be defined. Is it acute pain or chronic? Is it cancer-related or non-cancer related, et cetera? Third, the intensity of the pain should be graded, mild, moderate, or severe. Based on these three principles, the proper drug or drugs can be selected. In the case of acute shingles, pain is often severe in intensity and has both inflammatory and neuropathic components. It will require anti-inflammatory drugs for the inflammation. It will require an adjuvant drug for the neuropathic component, and due to its severity and acuteness, the use of a stronger opioids is likely indicated and justified as well. Fourth, the duration of required analgesia should be determined. In the case of a short painful episode, a short acting agent should be employed. If pain persist throughout the day, a long acting or sustained release drug should be chosen. Lastly, but certainly not least, the issue of safety needs to be addressed. If our patient is elderly and has a background of kidney problems, we'll avoid using NSAIDs, but we can still use an adjuvant or an opioids. If the patient has a drug problem in the past, we'll skip the opioids but still use the two other classes.
