Prescription Pain Relievers

(continued from page 36)

combined with an opiate, such as CoTylenol (codeine + Tylenol). When used in combination, the amount of drug needed can be lowered, and the risk of side effects, including addiction, is reduced. These combination drugs don't always work for severe pain, in which case the doctor may prescribe a stronger opiate drug.

The gold standard of opiate pain relievers is morphine. It was one of the first compounds extracted, isolated, and purified from the opium poppy, and it continues to be one of the most widely used pain relievers today. Morphine and other opiate drugs such as heroin, codeine, oxycodone, and hydrocodone have very similar chemical structures (Figure 3.2). However, other opiates such as fentanyl and meperidine (Demerol) have a slightly different structure (Figure 3.3).

Doctors are most likely to prescribe morphine or other opiates when pain is severe and expected to be short-lasting (a few days to a week), such as after injury or major surgery. This is because short-term use of opiates is less likely to lead to tolerance (loss of potency with repeated use of the drug) and dependence (addiction). However, the problem becomes more complex when the severity of the pain requires the use of pain-relieving medication for more than a few weeks, because this is when tolerance and addiction to opiates tend to develop (see the section on Opiate Addiction on page 48).

Table 3.1 on pages 44-45 lists commonly used opiate pain relievers. All opiates require a doctor's prescription. The medications differ primarily by their duration of action and the dose required to obtain sufficient analgesia.

Even with their outstanding usefulness as pain relievers, opiates have several side effects that can be serious. One of the most common side effects is that they are extremely sedating because they cause an overall depression of nervous system activity. This may significantly impair a person's ability to function at work or to drive a car. Opiates also tend to slow a person's breathing, and a complete stoppage of breathing is

Fentanyl Structure MeperidineKitchen Chemical Codeine
Figure 3.3 These are the chemical structures of fentanyl and meperidine (Demerol).

often the primary reason why opiate overdose results in death. A related problem is that opiates inhibit the cough reflex, which is why opiates are occasionally included in prescription cough medicines. (In fact, heroin was marketed as a cough suppressant in the late 1800s before its addicting properties led the U.S. government to ban it.) Other side effects of opiates are clouded thinking, constipation, dry mouth, nausea, vomiting, lowered blood pressure, sweating, and an inability to urinate. Some opiates induce the release of histamine from immune cells (refer to Chapter 2). This can cause itching and allergic reactions. Finally, tolerance, dependence, and addiction are particularly troubling side effects of opiates.

Continue reading here: How Opiates Relieve Pain

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