Chapter 10: Analgesics and Local Anesthetics

This chapter outlines the use of pain-relief preparations and their appropriate application in sports. The team physician should always be the person responsible for advising athletes regarding pain relief and prescribing these drugs. Sometimes athletes, coaches, and others will self-prescribe or encourage the use of analgesics or local anesthetics to allow players to participate in a contest. When recommending an analgesic or anesthetic to allow an athlete to participate in a practice or competition, the athletic trainer must be aware of the ramifications of this action. It is not our intention to outline the instances when using analgesic or anesthetic methods to allow a player to participate would be justified. We feel that participation by an injured athlete is a decision that must be made by the individual athlete in consultation with the team physician. It is well recognized that analgesics and anesthetics should not be used when further tissue damage is expected or may occur.

When an athlete experiences pain, this is an intrinsic signal from a body part indicating that something is wrong at some level in one or more of the tissues. The team physician should evaluate pain signals lasting more than a few days and refer the athlete to a specialist in pain management when it is deemed necessary. Injured athletes experiencing pain for short periods of time (less than a day) can use an over-the-counter (OTC) analgesic for short-term relief. If an athlete is in continuous pain for more than a day, he or she should seek the advice of a physician. The World Health Organization (WHO) has outlined a three-step approach to the management of pain. Table 10–1 outlines these recommended steps.

Many analgesics can be obtained OTC by the athlete and used without the knowledge of the team physician or athletic trainer. When this occurs, the pain experienced by the athlete can be masked, and participation on sports can lead to further damage to tissues. The athletic trainer and team physician should discourage frequent and independent use of analgesics for the purpose of participation. It is important to understand the normal system of pain control in the body. In the human body there is a pain control process initiated by the release of endogenous opioids to assist in diminishing pain perception when various problems occur. As mentioned previously, further pain control using prescription medications must be done under the direction of a physician.

Over the years the term "narcotic" has been associated with the opioid drug class. But, by definition, the term narcotic means "producing sleep or stupor,"13 which is an adverse effect, and not really the objective of, an opioid compound. Therefore, the more common description for this class of drugs is "opioids," a general term for morphine-type medications. Opioids are defined as "any drug containing or derived from opium." When physicians explain the use of opioids to the lay public, they also refer to similar synthetic drugs as opioids. There are many pain-control options, as outlined in Table 10–2, including both opioids and nonopioids as well as nondrug methods.

Analgesics in many different forms are available for pain relief. An analgesic is a drug or preparation that reduces or eliminates pain. Analgesics can be broken down into two basic categories: opioids and nonopioids. Opioid drugs were originally discovered as naturally occurring substances extracted from the opium poppy. The natural form is derived from the dried seeds of the poppy, which are processed to derive multiple active compounds. The opioids are well known for their ability to relieve moderate and severe pain symptoms. Drug manufacturers have developed semisynthetic and synthetic opioid derivatives that have effects similar to those of the naturally occurring form. Two of the best known compounds are morphine and codeine. Both morphine and codeine have similar chemical structures (Fig. 10–1) and both produce an analgesic effect in the body. With continued processing of the opium seeds, the drug heroin can be extracted. Thus it becomes apparent that this class of drugs is one in which physical dependence is a significant adverse effect.

Physical dependence signs and symptoms are typically demonstrated when a user stops taking the drug. An athlete who is physically dependent on an opioid will demonstrate withdrawal signs and symptoms such as irritability, sweating, insomnia, and tachycardia. An athlete who is psychologically dependent will exhibit behaviors that indicate he or she is craving or seeking the purchase of drugs. If the athlete is truly experiencing pain, the effect of addiction is diminished.

Endogenous Opioids

Endogenous opioids such as endorphins and enkephalins circulate throughout the body on an "as-needed" basis. The endorphins are naturally occurring morphinelike substances and are thought to bind to receptor sites on the pain-mediating pathways. The enkephalins have a similar function to that of the endorphins; they bind to different receptor sites but provide the same type of pain mediation. These endogenous opioids are considered more potent than morphine. Endogenous opioids are available to the central nervous system (CNS) for analgesic purposes. However, these endogenous substances do not exist in the same concentrations as exogenous opioids.

Opioid receptors have been identified in the peripheral nerves. Circulating endogenous opioids can bind to these sites and decrease the excitability of the peripheral sensory neurons, thereby providing an analgesic effect.¹¹ The endogenous opioids are thought to be more active in the peripheral tissues when one is dealing with an inflammatory process and analgesia is needed.¹⁰

The World Health Organization (WHO) has produced a treatment progression for physicians and others treating pain. The WHO outlined a three-step procedure (see Table 10–1) that health professionals can follow when addressing the problems associated with pain management. The WHO panel described pain in three categories: mild, moderate, and severe.

If the athlete is experiencing pain in the mild category, nonopioid medications such as acetaminophen, NSAIDs, or COX-2 inhibitors are recommended (see Chapter 3 for more details on these drugs). In the moderate pain category, if necessary, the physician may prescribe morphine or the related opioids such as hydrocodone and oxycodone. If the athlete is experiencing severe pain, the physician may choose methadone or a related opioid for pain control. The steps outlined in the WHO ladder (Fig. 10–2) give the medical provider good direction when helping an athlete to overcome pain for any situation. In some athletes there may be individual intolerances or contradictions to the use of NSAIDs or other drugs, which would indicate the use of an opioid for pain relief. Additionally, the athlete may need greater relief from pain, which may require an opioid drug. The physician should be the person who judges the severity of the pain that the athlete is experiencing and prescribes the proper analgesic for the level of pain. The specific drugs mentioned here will be discussed in more detail further on in this chapter.

Opioids' Mechanism of Action

Opioid receptors were among the first receptors in the brain to be characterized for a specific activity. In addition to receptors in the CNS, there are opioid receptors in peripheral tissues. The opioid receptors are classified into three categories: mu (μ), kappa (κ), and delta (Δ). Theoretically, any of the opioids can attach to any of the receptors and act as an agonist or antagonist. Typically, there are specific drugs that bind to one or two of the three receptors and cause a change based on the drug-receptor combination. When the physician prescribes an opioid, he or she is usually prescribing a mu receptor agonist, which results in pain relief. Sometimes drug-related euphoria is an adverse effect experienced from the use of this type of drug.

Some drugs have an agonist effect on the mu receptor and an antagonist effect on the kappa receptor. Additionally, it should be noted here that the mu, kappa, and delta receptors have other functions in the body. Alteration of their functions can result in an adverse effect of the drug. For example, a mu receptor agonist can also be associated with respiratory depression, pupillary constriction, changes in self-image, and increased energy. These and other adverse effects will be discussed further on in this chapter.

Opioid drugs act on the body by producing a decrease in neurotransmitter activity at both the presynaptic and postsynaptic sites, which alters the nocioceptive transmissions to the brain. The excitability of the neuron is altered as the opioid attaches to the potassium, calcium, or cyclic adenosine monophosphate (cAMP) activity at the synaptic site, resulting in a decrease in potassium or calcium conductance or cAMP second-messenger synthesis. These changes in activity at the synapse will result in changes at other sites along the neural pathway. In the case of the spinal cord, the opioid activity will result in an inhibition of the release of substance P (neurotransmitter) at the substantia gelatinosa. This decrease in substance P release produces an analgesic effect.⁶.

Exogenous Opioids

Physician Prescription

Opioid use must be prescribed and monitored by the physician. This class of drugs is tightly controlled in the United States, mainly because of the potential for addiction. When used properly, these drugs are generally safe and effective. Children and adolescents react to opioids in much the same way as adults. These drugs can be prescribed for both acute and long-term pain syndromes. A common use of opioids is to treat chronic pain in cancer patients. Their use for treatment of chronic noncancer pain was not common in the United States before the early 1980s. In athletics, the physician generally prescribes these drugs for acute pain, such as pain resulting from surgery or severe trauma.

Physicians use a set treatment plan when prescribing an opioid analgesic. This plan will most likely have the athlete taking normal dosages of the prescription drug initially, followed by small increases in the dose until the athlete begins to experience relief from the pain. The dosage will then be leveled off and the athlete will be slowly withdrawn from the drug. In most cases this takes less than a week. By then, the athlete should have suitable pain relief and can begin a rehabilitation program.

Specific Agents

According to Scott-Levin, a pharmacology consulting firm in Newtown, Pennsylvania, the single most prescribed drug in the year 2000 was hydrocodone with acetaminophen (APAP). Scott-Levin estimates that in more than 2.04 billion prescriptions for this drug alone were written in the year 2000. Table 10–4 outlines some of the more commonly prescribed oral opioid analgesics with which athletic trainers should be familiar in order to talk to athletes about their time of onset and duration of action. Hydrocodone (Vicodin, Lortab) is a semisynthetic narcotic analgesic that is combined with acetaminophen in some preparations. It also has an antitussive action and is used in several cough-suppressant formulations. However, this drug is more commonly prescribed for pain.

Oxycodone (prescribed under brand names including Oxy-Contin, Percocet, Percodan, Oxycodone, Roxicodone, Endocet, Roxicet, Roxilox, Tylox, Endodan, and Roxiprin) can be prepared in combination with acetaminophen or other similar analgesics. It is an opioid analgesic and, like other controlled drugs, must be prescribed by a physician. There is a high risk that an athlete will develop a tolerance if he or she uses this drug over a long period of time. These drugs can be abused by athletes and others, and the use of such drugs must be monitored by the athletic trainer. As with other opioids, this drug is contraindicated in conjunction with other CNS depressants such as alcohol.

Codeine is another mild to moderate agonist that can be prescribed by a physician or dentist to alleviate pain. It is also used as an antitussive for those experiencing severe coughing from the common cold or other upper respiratory tract infections. Codeine can also be habit forming, and the athletic trainer should be aware of any athlete who takes codeine for long periods of time. The most common complaint with the use of codeine is constipation.

Adverse Effects of Exogenous Opioids

As mentioned, this class of drugs can be addictive, which is an important concept for the athletic trainer to keep in mind. It is suggested that persons who have other addictive behaviors should be closely monitored when using these drugs. The ability of these drugs to become addictive suggests that the athletic trainer should monitor the athlete during the use of these drugs and discuss their use with the physician.

The opioids in general can cause sedation, nausea, vomiting, and constipation. The use of opioids with alcohol or other CNS depressants has an additive effect. Taking hydrocodone or other opioid drugs in combination with alcohol or other CNS depressants can be lethal. This is an important point to stress to the high school or college athlete who may be experimenting with or using alcohol regularly. Respiratory depression when taking opioids, and other drug interactions with alcohol or CNS depressants, all of which may cause other health problems or even death, must be explained to the athlete.

As mentioned previously, the physician will prescribe only a limited amount of an opioid drug after surgery to help reduce the associated pain. In most situations, an athlete will be using the drug for less than 10 days, so the opportunity for developing tolerance or dependence is decreased. If the athletic trainer notices that an athlete is taking an opioid for longer periods of time, it may be that the athlete is obtaining extra medication from multiple sources. Suspicion of inappropriate use should be reported to the physician immediately. In a published article by Jonasson et al.,⁵ 22 percent of the orthopedic and chronic pain population they interviewed was considered to have an analgesic use disorder. An even higher percentage, 33 percent, met the criteria for having a substance use disorder.

It is recommended that physicians be aware of whether a patient has addictive behaviors before they prescribe an opioid for analgesia. Coambs et al³ (1996) developed the Screening Instrument for Substance Abuse Potential (SISAP) (Table 10–5). The athletic trainer can implement it and convey the information derived from it to the team physician.

It should also be remembered that many prescription opioid pain relievers are combined with acetaminophen or aspirin. The maximum amount of acetaminophen that an athlete with a healthy liver can safely take is 4000 mg per day. If the athlete uses alcohol or has impaired liver function, the maximum daily amount is 2000 mg. People with liver failure should not take acetaminophen. Acetaminophen and aspirin are included in many OTC products also. The athlete should carefully read the label of each OTC drug he or she is considering using to determine all of the ingredients it contains. The athletic trainer should check with the physician or pharmacist to determine if any extra acetaminophen or aspirin can be taken along with the prescription medication.

As mentioned previously, the opioids are known to induce a tolerance effect in some individuals. Tolerance in this situation means that an increasing amount of the drug is required to maintain the same level of analgesia. Tolerance development can be affected by dose, frequency of administration, and regularity of dosing. In the case of the opioids, an increase in tolerance alone does not indicate that a person is addicted to the drug, but an increased tolerance can be a part of the addiction process. It has been shown that 10 to 20 times the initial dose may be needed to control pain in some drug-tolerant individuals. Even though a tolerance effect can start in the first days of taking an opioid, it is not common, and the typical athlete's regimen of taking the drug for less than a week seldom initiates a tolerance response. Tolerance is an important concept for the athletic trainer to understand because tolerance development is normal and expected when opioids are used for long periods of time. The physician can increase the opioid dosage over time. Athletes (and all patients) need to be reassured that this increased dosage does not mean that they are becoming addicted to the medication. When opioids are prescribed for a pain-related condition, addiction does not commonly occur.

Occasionally, opioid drugs can cause respiratory depression and orthostatic hypotension, even at normal doses. The key physiological signs to look for in an athlete possibly overusing these drugs are reduction of respiratory rate and depth, somnolence, euphoria, sedation, slurred speech, and judgment difficulties. If these adverse effects are noted, the dose may be too high or the patient may be overdosing himself or herself. These drugs have an additive effect when combined with other CNS depressants. Ingesting opioids in combination with alcohol or other CNS depressants can result in severe side effects. Opioids taken in conjunction with other CNS depressants have been identified as causes of accidental and self-inflicted fatalities.

As mentioned previously, opioids can create sedation, drowsiness, and an overall mental slowdown. It is wise to schedule rehabilitation or other activities that require mental acuity at times when the drug is at a period of reduced activity. Another possible adverse effect of the opioids is a perception of euphoria, mood changes, or relief from anxiety, which varies from athlete to athlete. This is an adverse effect that needs close monitoring by the physician with help from the athletic trainer.

Because the opioids have an antiperistaltic action, constipation can be an unwanted adversee effect. The physician needs to be aware of any constipation that the athlete may be experiencing. Treatment regimens are available for opioid-associated constipation and should be followed when the athlete is experiencing this adverse effect. Nausea or vomiting can be a problem at lower doses, although at higher doses the vomiting response can be depressed.⁹ Taking the medication with food often helps with opioid-associated nausea.

Nonopioid Preparations

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used widely for management of pain as well as inflammation. Because of the many types and wide uses of these drugs, we have dedicated a chapter to the anti-inflammatory drugs. Please see Chapter 3 for more information regarding NSAIDs.

One of the most popular nonopioid prescription medications is propoxyphene (Darvon, Darvocet, Darvon-N), which is a mild to moderate agonist. Propoxyphene has a high propensity for addiction among users and has a significant toxic effect when used with other CNS depressants. The toxic effect is mainly depression of the CNS, which results in respiratory difficulty and/or failure. This drug is now prescribed for pain control only on an occasional basis. Propoxyphene ranks second to barbiturates in causing prescription drug fatalities.

Another OTC preparation that is being used more and more is capsaicin, also marketed by the trade name Zostrix. Capsaicin is derived from the seeds of hot chili (capsicum) peppers such as habañero, Jamaican hot, cayenne, and jalapeño. Researchers now have determined that capsaicin limits the activity of substance P in transmitting pain messages from the extremities to the brain.² Capsaicin is generally marketed for arthritic individuals or persons with some type of atypical pain such as shingles or other neuropathic pain. However, athletes are discovering the use of this product, which is topically applied as a cream. The OTC preparations have a smaller percentage (0.025–0.075%) of the active ingredient, but there are products being tested that have 5 to 10 percent capsaicin. The higher concentrations appear to provide some analgesia and pain relief.⁸

The athletic trainer should be fully aware of whether the athlete is using any OTC preparation before participation in activity. An athlete should not use an analgesic to mask any pain. When an athlete is not physically ready for practice or competition, he or she should not use an analgesic in an attempt to overcome any warning signals the body may be sending to avoid tissue damage.

Athletes' Understanding of Analgesic Drugs

It is interesting to review the comments of collegiate athletes questioned about "painkilling drugs" and the use of those drugs. In a study reported by Tricker,¹² over 2/3 of 563 athletes surveyed responded that they were aware that painkilling drugs were potentially addictive. When asked for a self-report on the use of such drugs, more than half of the athletes indicated that they used painkilling drugs when injured, sick, or sore after workouts, regularly throughout the season. The athletes in this study generally considered themselves to be overusers of painkilling drugs. Additionally, they reported that they did not obtain the painkilling drugs from physicians, but rather from sources such as teammates, friends, and parents. The actual types of painkilling drugs used were not reported in this study, but it gives a sense of how many athletes are using drugs that produce analgesia.

The physician and athletic trainer should monitor any OTC medications taken by the athlete that produce analgesia because a reduction in pain may allow further tissue damage if an athlete participates without regard for the internal warning signals his or her body produces. Additionally, the athlete should report any use of herbal preparations because of the possibility of adverse interactions between many analgesics and herbal medications. Some herbal medications (such as echinacea and kava-kava), when used in conjunction with OTC or prescription analgesics (such as acetaminophen and opioids, respectively), can lead to hepatotoxicity and nephrotoxicity, among other problems. The effectiveness of some analgesics can be inhibited by herbal supplements. A good review of the potential for adverse interactions between herbal medications and analgesic drugs is available in the recent article by Abebe.¹

The athletic trainer should observe athletes whom they suspect of overusing analgesics for indications of euphoria, judgment difficulties, and excessive sedation or sleepiness. The athlete might also suffer from respiratory rate reduction. It is not uncommon for an abuser of analgesics to attempt to obtain additional prescriptions for the medication from multiple providers. This allows the abuser to take more of the drug, which keeps him or her in an altered state more often.

The term local anesthetic denotes a drug or preparation used to produce partial or complete loss of sensation in a specific area. Typically, this is done by injection, but a decrease in sensation can also be accomplished by using an ice pack. In this chapter section we discuss drugs that are injected to accomplish this sensation reduction.

Local anesthetics are commonly used in a physician's clinical practice. The origin of local anesthetics goes back to the 1500s, when the Incas used the coca leaf as a local anesthetic. Late in the 1800s, cocaine was derived from the coca leaf and a liquid solution of cocaine was used by physicians for local anesthetic purposes. You will note as you study this chapter that many of the local anesthetics have a "caine" suffix. This derives from the original use of cocaine as an anesthetic. The main advantage of using a local anesthetic in the late 1800s and early 1900s was that it avoided the need to use general anesthesia, which then had a very high associated risk of mortality.

Clinically, there are times when the use of an anesthetic to impair sensation is desirable. Examples of these situations are the repair of a laceration with sutures by a physician or when the dentist is performing a simple procedure and needs to eliminate the pain signal being transmitted to the CNS. In addition to decreasing the pain sensation, local anesthetics have the ability to depress other excitable tissues. Other areas that can be affected by a local anesthetic are the brain, heart, and muscles. Compared to general anesthetics, local anesthetics allow more rapid recovery and have few, if any, residual effects such as lethargy or confusion.

Anesthetics targeted for local activity are administered peripherally because systemic usage does not allow the drug to be effective because of dilution, absorption, or metabolism as it is transported to the site.

Epinephrine is often added to local anesthetics to provide a longer duration of action. The rationale for adding epinephrine is to cause vasoconstriction in the targeted area, which diminishes blood flow and reduces absorption of the anesthetic from the site of activity. Injection of the drug to the desired site allows for almost complete bioavailability of the drug to the area. On injection, the drug rapidly moves away from the injection site. Figure 10–3 illustrates the absorption of anesthetics into different tissues of the body. If the concentration of the anesthetic is appropriate, it will diffuse across the membrane barriers, where it will begin to affect the outer fibers of the nearest peripheral nerve, followed by the inner part of the nerve. After the drug starts to be metabolized by the body, the anesthetic effect begins to diminish. The outer fibers recover first, followed by the more central sections of the nerve. Depending on the type of anesthetic used, this entire process can take from minutes to hours.

A local anesthetic drug affects the nerve fiber by diminishing the ability of the nerve fiber to conduct action potentials and by inhibiting the number of nerve endings that can transmit impulses to the CNS. The local anesthetic does this by inhibiting the Ca+ and Na+ activity and the propagation of impulses along the nerve pathways. Thus, the ability of the CNS to receive pain stimuli is decreased and the person does not feel the stimulus being applied to a specific section of the body. After the anesthetic has remained in the area for a period of time, the patient begins to lose motor control and other muscular activities (including proprioception) at the site of the injection.

Local anesthesia can also be used to provide local analgesia for conditions such as musculotendinous or joint pain. The same basic principle of blocking afferent nerve transmission is applicable in these situations. However, the use of local anesthetics to allow an athlete to participate is much more controversial when the athlete is experiencing musculotendinous or joint pain. For example, an athlete with a mild ligament sprain may be experiencing pain from the initial injury. There might be situations in which the use of a local anesthetic would be appropriate to allow the athlete to participate. The decision to allow an athlete to continue participating after the injection of a local anesthetic must be made by a competent licensed medical practitioner.

Delivery and Use of Local Anesthetics

The physician has a number of choices for the application of local anesthetics. Delivery of local anesthetics can be simple, such as applying an ice pack or a topical preparation such as ethyl chloride spray, or sophisticated, such as using an injectable preparation. Topical anesthetics are not as effective as those used within the body. Topical application is also called transdermal delivery because the drug has to pass through the skin. Topical application is used for various minor skin irritations. General absorption rates for local anesthetics are presented in Figure 10–3. Parenteral administration (injection) is most often used for suturing or dental work. Peripheral nerve blocks involve the injection of an anesthetic close to a nerve trunk to block afferent transmission in minor surgical procedures and tooth extraction and in relieving chronic pain conditions. Anesthetics can also be used as a central nerve block or as a sympathetic nerve block, usually in connection with more serious conditions not typically associated with athletic participation. The physician should determine the amount, duration, and delivery method of a local anesthetic.

Ice can be a semi-effective anesthetic for reduction of local pain from a sprain or strain, or to decrease temperature and touch sensation in a limited area. The athletic trainer who uses an ice treatment must be careful to watch for allergic reactions such as urticaria. It is also important to make sure the athlete does not have reduced sensation to an area that could receive further tissue injury if improper stresses were applied.

Other topical anesthetics are used for relief of symptoms or for minor procedures. Topical anesthetics may be composed of one or a combination of drugs, and may be applied to the skin, mucous membranes, cornea, or other areas. The physician, rather than the athletic trainer, should be the primary person monitoring an athlete's use of topical anesthetics.

Commonly Used Local Anesthetics

Many years ago, procaine (Novocain) became the first widely used injectable anesthetic. In the mid-20thcentury, other local anesthetics were produced that had better anesthetic properties. However, the term "Novocain" is still sometimes used by the lay public as a generic term for a local anesthetic. Other common local anesthetics and their effects are outlined in Table 10–6. These local anesthetics have similar mechanisms of action and are chosen by the physician based on relevant individual differences among them, such as their duration of action, onset of action, and safety profile.

Cocaine

The origins of cocaine go back to China, where the use of the opium poppy was originally confined to medicinal purposes. Medical practitioners used cocaine for hundreds of years before it became a drug of abuse by a small portion of the population. Today cocaine can be used in surgical situations when the physician deems it appropriate for use as an anesthetic. Cocaine is still used in some nasal surgeries in a controlled surgical setting as a local anesthetic with vasoconstricting properties. The athlete and general public should understand that cocaine can be toxic and lead to multiple health problems.

Unfortunately, too many people, including some athletes, have determined that cocaine can provide a stimulatory and psychological effect when used for personal pleasure. Cocaine is a highly addictive drug and has extremely serious adverse effects, up to and including death. Athletic trainers should use their role to discourage athletes and other people from using cocaine recreationally any time the opportunity arises.

Physician Use Considerations

There are three main considerations when a physician uses a local anesthetic. First, time to effect. How long does the drug take to cause enough reduction in pain sensation to begin the surgical procedure? Second, length of time the anesthetic will remain in effect. How long will the drug continue to decrease the pain sensations so that the procedure can be completed? Third, what are the adverse effects? Are there adverse effects that must be considered with respect to the person receiving the local anesthetic? Does the person have heart problems that could be exacerbated by a specific type of local anesthetic? What are the dosage and toxicity limits for this person? The physician should be very familiar with the adverse effects and correct dosages of local anesthetics. If local anesthetics are used illegally or improperly by someone not trained in correct dosages, there can be very serious adverse effects to the athlete.

Adverse Effects of Local Anesthetics

Local anesthetics can have serious and toxic effects if used in excessive dosages. There is a possibility of overdose. An overdose of a local anesthetic can result in multiple problems. There can be altered CNS activity, including both excitation and depression. Signs of CNS excitation can include confusion, agitation, generalized excitation, and seizures. CNS depression can be exhibited as decreased respiration and somnolence. Other possible adversee effects of anesthetics include allergic reactions and cardiac arrest, sometimes leading to death.⁷ This class of drugs should not be used by untrained people. There are times when an athlete may want to use a local anesthetic to reduce the feeling in an area so that he or she can compete. Always make sure that the physician controls the use of local anesthetics in athletes.

What's Next?

Curatolo and Bogudk4 provide an overview of current pain treatments and a brief introduction to new analgesics and anesthetics that are being developed. Techniques are currently being investigated that will utilize biodegradable polymers to encapsulate local anesthetics to provide a longer duration of action. Additionally, researchers are working on developing new types of local anesthetics that will block only the nocioceptive impulses and reduce or eliminate the blocking of motor impulses and reduce sensory losses in the local area. They are also working on other types of analgesics that could change the way in which pain is controlled. Some of these new substances include N-methyl-D-aspartate (NMDA) receptor antagonists and cannabinoids. NMDA receptor antagonists appear to affect hyperalgesia and hypersensitivity centrally. Cannabinoids are a derivative of the cannabis plant, which has been used for many years to treat a variety of illnesses. In animal research studies, the cannabinoids appear to reduce pain in a number of experimentally produced pain situations without causing nausea.

1. Which of the following opioid receptors are not located in the brain?

   1. Kappa

   2. Sigma

   3. Delta

   4. Mu

2. Opioid drugs work by which of the following mechanisms?

   1. Decreasing neurotransmitter activity

   2. Increasing neurotransmitter activity

   3. Increasing peripheral vascular activity

   4. Decreasing peripheral vascular activity

3. Endogenous opioids are:

   1. Available for athletes OTC

   2. Taken by the athlete on an "as needed" basis

   3. Produced by the body on an "as-needed" basis

   4. Found in high concentrations when pain occurs in the body

4. True analgesic medications:

   1. Decrease inflammation

   2. Decrease fever

   3. Decrease pain

   4. Increase blood flow

5. Opioids should not be combined with:

   1. Tobacco

   2. Food

   3. Carbonated drinks

   4. Alcohol

6. What substance was one of the first local anesthetics and is still used medically today, but is illegal for use by the general public?

   1. Procaine

   2. Cocaine

   3. Aspirin

   4. Lidocaine

7. Opioids can induce a tolerance effect during the first week of use.

   True  False

8. An overdose of a local anesthetic can result in the death of the athlete.

   True  False

9. Other than pain, opioids can be prescribed to control:

   1. Weight gain

   2. Cardiac arrhythmias

   3. Eating disorders

   4. Coughs

10. A local anesthetic will eliminate total pain from the entire extremity that it comes in contact with.

    True  False