The most common analgesic side effects can range from gastrointestinal discomfort to nausea to severe organ dysfunction, depending on the dose as well as the category of a particular analgesic drug. Typically, analgesics are classified as either narcotic medications, also known as opioids, or as non-narcotic medicines. Some drugs that do not strictly fit into these categories have pain-relieving properties. Aspirin and non-steroidal anti-inflammatory drugs, or NSAIDs, fall under the classification of medications that can have analgesic-type effects. Each of these types of pain-relief medications can have specific side effects, and higher doses sometimes produce more severe side effects.
Acetaminophen, known in some areas as paracetamol, is typically available without a prescription for the relief of moderate or mild pain. Although this drug is considered safe when users follow the manufacturer's dosing instructions, serious analgesic side effects can result in the case of long-term consistent use or if an overdose occurs. Damage to the liver or kidneys is possible if an individual engages in excessive dosing or has cumulative, consistent use over a long period of time, or combines this drug with the use of alcohol. For any person who is taking acetaminophen or paracetamol for pain relief, care should be taken to avoid combining this individual medication with any other medicinal preparation that also contains the same drug as an active ingredient.
Opioid or narcotic medications, which are often used in individuals with severe or chronic pain conditions, are likely to produce analgesic side effects in many individuals, particularly at the onset of treatment. The most commonly occurring analgesic side effects associated with opioid medications are vomiting, itching, constipation, sleepiness, low blood pressure when standing up, contracted pupils, dry mouth, and retention of urine. Individuals who take narcotic drugs tend to develop a tolerance for the medication over time, resulting in high doses that would be severely damaging or fatal to a person who was not yet accustomed to these drugs. One of the possible analgesic side effects of a high dose of narcotic medication could include depression of the respiratory system. Some commonly used opioid medications include codeine, morphine, hydrocodone, fentanyl, and tramadol.
Analgesic side effects are also possible with the use of NSAIDs, such as ibuprofen. Some severe effects that have been associated with inappropriate use of NSAIDs include hearing loss, renal failure, ulcers, or internal bleeding. Aspirin is never appropriate for use in children under 16 years old, due to the possibility of developing a liver disorder called Reye's syndrome. Certain drugs like celecoxib that originated from NSAIDs, called COX2 inhibitors, can result in a higher risk of heart problems.
One way to avoid systemwide analgesic side effects in certain cases is to use topical medications. Injections of lidocaine or frequent applications of an analgesic gel might be available for relief of joint pain, for example. Capsaicin is one type of topical analgesic that could be used for pain relief in some individuals.