This is an excerpt from Core Concepts in Athletic Training and Therapy With Web Resource by Susan Kay Hillman.
The two main types of analgesics are both used for pain, yet the stronger, more addictive narcotic pain relievers are reserved for severe pain such as postoperative pain or pain from serious tissue damage.
Narcotic pain relievers have a limited use for most sport injuries. Moderate to severe pain, such as acute pain following a significant injury or surgery, is often treated with prescription drugs rather than the OTC agents. Narcotic analgesics of the opioid family provide excellent relief from this more severe pain because of their ability to bind within the central nervous system and interrupt nociceptive (pain) transmission. Opioid analgesics, however, have a negative side: They can cause physical as well as psychological addiction. This fear of addiction is typically not a concern in the treatment of acute traumatic injury because the duration of use of the narcotic drug is very short. Long-term use of narcotic painkillers, on the other hand, should be avoided because of the increased risk of drug dependence. In the mid-1990s a very prominent NFL star openly admitted to having become addicted to pain medications taken during the football season. Following this public announcement, most individuals and sports medicine specialists began looking more critically at their use of pain medications. Masking pain to allow someone to participate is certainly not condoned by the medical community and should never be done without careful protection of the injured area to avoid exacerbation of the problem.
Among the opiates, three specific drugs are familiar to the general public: morphine, codeine, and heroin. Heroin is not used for sports medicine needs and is not discussed here. Morphine is used to relieve moderate to severe pain and is often used as the standard with which other prescription analgesics are compared. Codeine is frequently the analgesic of choice for oral preparations of medicinals to control postsurgical or severe pain.
Endogenous opioids are a group of opioids that are produced in the human body and are often referred to generically as endorphins, yet there are actually three groups of endogenous opioids: endorphins, dynorphins, and enkephalins. Endogenous opioids are manufactured in the brain and released as the body attempts to control pain. They have specific receptors in the central and peripheral nervous systems, giving them a very direct avenue of action; yet endogenous opioids are not as potent as the exogenous opioids. Exogenous opioids such as morphine, codeine, and heroin are either natural (from a plant), semisynthetic (from a plant and also manufactured), or synthetic (manufactured).
Opioid receptors have been the subject of much detailed research since their discovery. That there is more than one type of opioid receptor has been well documented. It has also been documented that the different receptors allow different effects to occur. Not only are the effects of the opioids controlled by the receptors, but the side effects also vary according to the particular receptor.
Generally, the nonnarcotic analgesics are the same drugs as the NSAIDs (including aspirin and salicylates), since the NSAIDs are able to work in both capacities (analgesic and anti-inflammatory). Salicylates, ibuprofen, and acetaminophen are the most common names associated with OTC analgesics. Salicylates and ibuprofen products are NSAIDs; acetaminophen is the only nonnarcotic that is not also an NSAID.
Both the analgesic and the anti-inflammatory actions of salicylates are believed to be caused by peripheral inhibition of prostaglandin synthesis as with the other NSAIDs. However, in contrast to other NSAIDs, aspirin may also inhibit the action and synthesis of other mediators of inflammation.
Antipyretic effects of salicylates are a result of inhibition of prostaglandin synthesis in the hypothalamus rather than at the local site as in their other actions. Aspirin also may increase the blood flow to the skin and cause sweating, thus dissipating heat associated with a fever.
Another analgesic that is not an anti-inflammatory is acetaminophen (Tylenol, Datril, Pamprin, and Panadol). Acetaminophen is a weak prostaglandin inhibitor in the peripheral tissues. Its effect is similar to that of aspirin in diminishing pain or fever, but it is not at all helpful in the reduction of inflammation. Acetaminophen is the analgesic of choice when the patient is allergic to aspirin or has intolerance to salicylates. Children with viral infections may be treated with acetaminophen without the risk of Reye's syndrome associated with use of aspirin products.
Acetaminophen is very useful in the treatment of mild to moderate pain and is provided in OTC strengths of 325 and 500 mg in tablet, capsule, and liquid-preparation forms. In Europe, paracetamol is the equivalent to acetaminophen and is quite readily available. Liquid acetaminophen preparations are also available, which is helpful when acetaminophen is needed for intraoral injury or for surgery involving the jaw or mouth.
A narcotic agent to increase the drug's potency may supplement acetaminophen. This combination, such as Tylenol III or Tylenol IV, is often used for the treatment of severe pain associated with fractures, dislocations, or other trauma, including surgery. The narcotic (usually codeine) adds the analgesic effect of the narcotic pain reliever to that of the acetaminophen; the narcotic-supplemented acetaminophen is therefore a high-level analgesic limited in its use to patients with severe pain. Acetaminophen with codeine (Tylenol III, Tylenol IV) is a controlled prescription drug because of the narcotic; thus its use is strictly monitored.
Administration of Analgesics
Analgesics have a wide variety of routes of administration, probably because of the wide variety of situations in which pain is the dominant complaint.
Analgesics are most commonly taken by mouth in either a pill, capsule, or liquid form but may also be given transdermally by iontophoresis or a specialized patch, by injection into a muscle, or intravenously. You may hear of a patient having an analgesic “pump” following surgery. This most often involves one of the narcotic pain relievers, and the pump allows the patient to administer small doses of the drug as the pain dictates, always with the machine preventing an overdose of the medicine.
Adverse Effects of Analgesic Therapy
The most common unwanted effects of opioids include drowsiness, dizziness, blurred vision, nausea, vomiting, and constipation. Addiction to opioid drugs, as previously stated, is also a risk from both a physical and a psychological point of view. There is clear, documented evidence that morphine causes a physical addiction—as evident in the severe withdrawal symptoms experienced by addicts when the drug is no longer available. At first the patient feels uneasy or nervous and may experience depression. Physical signs of addiction occur during withdrawal and include sweating, nausea, and vomiting. Muscle tremors and twitching are also associated with narcotic withdrawal. Withdrawal symptoms can last anywhere from 36 h to 5 days. After this withdrawal period, the person may still have a strong psychological addiction to the drug, such as a strong desire or craving for a “fix.” Psychological addiction can last for years and is often thought to be the most difficult part of the addiction and withdrawal process.
As we discussed earlier, aspirin inhibits platelet function, but the body's blood-clotting mechanisms usually begin to return to normal within 36 h after the last dose of the drug. Other salicylates have minimal effect on platelets, and acetaminophen has no effect on the platelets.
Gastrointestinal irritation is fairly common with the use of many of the NSAIDs and salicylates but less common with the COX-2 inhibitor classes. Aspirin and buffered aspirin products have approximately the same absorption rate; however, the incidence of bleeding is reported to be higher with plain aspirin tablets than with the buffered products. Gastrointestinal mucosa injury is seen less often with coated aspirin than with plain aspirin or buffered aspirin. Patients with erosive gastritis or peptic ulcer should avoid salicylates because of the possibility of exacerbating the condition.
Tinnitus and hearing loss associated with salicylate therapy are dose related and usually completely reversible, typically subsiding within 24 to 48 h after the dose is reduced or discontinued.
Implications for the Athletic Trainer
It is important to understand the types of analgesics available for the treatment of pain. Although you will not prescribe drugs, you should be able to inform the patient regarding the type of analgesic prescribed or what might be expected following a surgical procedure. Additionally, understanding of the various alternatives for pain medication may prove beneficial in helping patients decide wisely when selecting an OTC analgesic for minor pain.