Fentanyl side effects

Morphine has certain undesirable side effects. Among these are respiratory depression, nausea, and vomiting, depression of the cough reflex, cardiovascular depression and hypotension, smooth muscle contraction (constipation), and histamine release (93). Morphine s onset of action, duration, and low therapeutic indices have prompted a search for a more effective opiate iv anesthetic. Extreme simplification of the complex morphine molecule has resulted in anilido —piperidines, the fentanyl class of extremely potent opiate iv anesthetics (118,119). 

Severe pain should be treated with an opioid such as morphine, hydromorphone, methadone, or fentanyl. Moderate pain can be treated effectively in most cases with a weak opioid such as codeine or hydrocodone, usually in combination with acetaminophen. Meperidine should be avoided owing to its relatively short analgesic effect and its toxic metabolite, normeperidine. Normeperidine may accumulate with repeated dosing and can lead to central nervous system side effects including seizures. 

Users of fentanyl analogues report that these drugs produce a rapid rush or euphoria that is similar to that felt with heroin, followed by a sedated, dream-like state. As analgesics, they also produce a profound loss of pain sensation and have common unwanted side effects such as sleepiness and constipation. However, because they are so potent, fentanyl analogues can... 

Among the compounds that fall within this class are hydrocodone (e.g., Vicodin), oxycodone (e.g., OxyContin—an oral, controlled-release form of the drug), morphine, fentanyl, codeine, and related medications. Morphine and fentanyl are often used to alleviate severe pain, while codeine is used for milder pain. Other examples of opioids prescribed to relieve pain include propoxyphene (Darvon) hydromorphone (Dilaudid) and meperidine (Demerol), which is used less often because of its side effects. In addition to their effective pain-relieving properties, some of these medications can be used to relieve severe diarrhea (for example, Lomotil, also known as diphenoxylate) or severe coughs (codeine). 

After passage through the blood brain barrier, opioids have an anti-emetic effect (Blancquaert et al., 1986). Emesis inhibition is induced via blockade of an emesis centre located in a more central area of the formatio reticularis. This explains why the emetic effect of opioids is most apparent immediately after anministration, especially after rapid intravenous administration and is reduced or terminated when the compound has reached the CNS. The more hydrophilic opioids like morphine have stronger emetic side-effects than lipophilic compounds like methadone or fentanyl (Barnes et al., 1991), which are rapidly transported into the CNS. 

Side-effects The side-effect profile (Poklis, 1995) is typical of potent p-opioids with respiratory depression, increased muscle tone (chest wall rigidity during fentanyl anesthesia), strong sedation and emesis being most prominent. Adverse reactions can be antagonized with naloxone. 

A quantum leap in pain therapy with distinct advantages in the form of reduced side-effects and application frequency was achieved with transdermal opioid administration. Transdermal application requires a number of characteristics on the part of the active substance (Fig. 7), the most restrictive being the daily dose, and only very potent opioids which are effective in very low doses, such as fentanyl and buprenorphine, are an option (Sittl and Likar, 2001). 

Within the last 10, years several new compounds were launched in the field of non-steroidal antiinflammatory drugs (NSAIDs) with a clear focus on cyclooxygenase type 2 selective compounds. In the field of opioids on the other hand no new drugs have passed phase III clinical trials. In this field innovation has been achieved through new pharmaceutical formulations of known drugs such as transdermal systems, e.g. buprenorphine patch, transmucosal systems, e.g. fentanyl lollipop, or rectal delivery systems containing e.g. morphine. These were developed in order to reduce opioid side effects, but also to overcome pharmacokinetical limitations, in particular to prolong compliance and duration of action. 

Fentanyl is primarily used alone, but sometimes it is combined with other opiates such as Licodaine, Bupiva-caine, or morphine in epidural administration or in some I Vs. However, one of the more appealing virtues of fentanyl is that, unlike other opioids, it has a very mild effect on the emetic trigger zone of the medulla. For this reason, patients have less nausea and no vomiting when fentanyl is used. With other drugs, such as morphine, this unwanted side effect can be intense. Fentanyl also does not cause the release of histamine, which makes it safer for the cardiovascular system than morphine. 

Recently fentanyl has been tested on AIDS patients. The drug is useful in blocking pain receptors, which helps patients cope with their pain. It also helps AZT to cross the blood-brain barrier. When used alone, AZT also has several side effects that early testing has shown to be reduced when fentanyl is added to the treatment. 

Some other rare side effects from fentanyl include breathing difficulties, wheezing, cold and clammy skin, seizures, slow or fast heartbeat, severe rash, and unusual weakness. A physician should be notified immediately if any of these symptoms occur. It is more common for patients to experience confusion, fainting spells, and nervousness or restlessness any of these also need medical attention. Some side effects that do not require immediate medical attention but can be reported if bothersome include itching, blurred vision, clumsiness, difficulty urinating, headache, and nausea. 

One of the side effects of fentanyl is drowsiness, so any other medication that causes drowsiness can greatly increase this effect in a user. For this reason, users of fentanyl must not consume alcoholic beverages, because a user can fall asleep quickly and possibly depress the user s respiratory system even more. Some medications to be avoided include barbiturates, antidepressants, tranquilizers, muscle relaxants, and antihistamines used in some cold medicines. 

Patients taking naltrexone (trade name Trexan) must tell their health care professional because the two drugs will cancel any effects that the other has. Some other medications that reduce the effects of fentanyl are buprenorphine, dezocine, nalbuphine, and pentazoncine. These medications also can cause side effects in people who have become physically dependent on fentanyl. 

Studies in animals and primates with these highly selective delta agonists begin to reveal that unlike mu opioid agonists such as morphine, oxy-contin, fentanyl, etc., agents acting at the delta receptor are unlikely to produce addictive liability and respiratory depression. In fact, delta agonists may actually counteract those side effects induced by mu opioids. 

Payne R, Mathias SD, Pasta DJ, Wanke LA, Williams R, Mahmoud R. Quality of life and cancer pain satisfaction and side effects with transdermal fentanyl versus oral morphine. J Clin Oncol 1998 16(4) 1588-93. 

Lo WK, Chong JL, Chen LH. Combined spinal epidnral for labour analgesia—duration, efficacy and side effects of adding sufentanil or fentanyl to bupivacaine intrathecaUy vs plain bupivacaine. Singapore Med J 1999 40(10) 639 3. 

Shipton EA. Pruritus—a side-effect of epidural fentanyl for postoperative analgesia. S Afr Med J 1984 66(2) 61-2. 

Fentanyl is used chronically in the management of major pain in humans. One of the common side effects of therapy with opioids is constipation. However, a recent cohort analysis of a large California HMO looking at the incidence of constipation in patients receiving opioid analgesics showed a low incidence of constipation in the patients receiving fentanyl patches (3.7%). 

Fentanyl, sufentanil, and alfentanil are frequently used before anesthesia and surgery as a sedative and analgesic, as well as a continuous infusion for primary anesthesia. Because opioids rarely affect the cardiovascular system, they are particularly useful for cardiac surgery and other high-risk cases. Opioids act directly on spinal cord receptors, and are frequently used in epidurals for spinal anesthesia. Side effects may include nausea and vomiting, itching, and respiratory depression. 

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