Fentanyl IV/IM Formula (Sublimaze®)
Last Modified: January 4, 2016
Opioids are the strongest form of medication used to treat pain. Opioids work by attaching to specific proteins called opioid receptors, which are found in various organs of the body including the brain, spinal cord and gastrointestinal tract. An opioid will attach to the opioid receptor, which then reduces the transmission of pain messages to the brain, therefore reducing pain. Opioids are used to treat moderate to severe pain that is not well managed with other pain medications. However, they do not treat the underlying cause of the pain. If a cancer is causing the pain, any cancer treatment is working to reduce pain related to the cancer.
There are many different formulations of fentanyl. This form is given intravenously (directly into a vein) or intramuscularly (an injection into a muscle). It is used for both short-term pain management and as an anesthesia. This article will focus on the use of intravenous fentanyl for pain management.
How to Take Fentanyl
This type of fentanyl is given intravenously (into a vein) or injected into a muscle. Your doctor will determine the exact dosage and dosing schedule. When Fentanyl is injected, it is immediately absorbed into the body. It will begin working to relieve pain almost instantly, although it reaches its peak effect in 5 to 10 minutes. It will continue to work for 2 to 4 hours.
This medication can interact with alcohol and other medications that depress the central nervous system like barbituates (including phenobarbital), tranquilizers (including Haldol®, Librium® and Xanax®), other narcotics and general anesthetic. Make sure your provider is aware of all the medications, vitamins and supplements you are taking.
Possible Side Effects of Fentanyl
There are a number of things you can do to manage the side effects of fentanyl. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:
Constipation is a very common side effect of pain medications, but one that can often be managed with an ounce of prevention. Be sure to drink 8-10 glasses of water a day. Warm or hot fluids can be helpful. Increase physical activity when possible. Attempt a bowel movement at the same time each day. It is helpful to eat plenty of fruits and vegetables. Some folks do find that 4 ounces of prune juice or 3-4 dried prunes/plums help promote bowel movements. However, high fiber foods (ex. bran flakes, high fiber cereals) and fiber supplements (such as Metamucil) can actually make constipation from pain medications worse and should be avoided.
Your doctor or nurse may recommend a bowel regimen, using stool softeners and/or laxatives, to prevent or treat constipation. Stool softeners (such as docusate sodium or Colace) work by bringing water into the stool, making it softer and easier to pass. A stimulant or laxative (such as Bisacodyl, Dulcolax, or Senakot) works by stimulating peristalsis, moving the stool through the bowel. Your provider may recommend Miralax (Polyethylene glycol 3350), which is an osmotic laxative. It works by causing water to be retained in the stool, softening the stool so it is easier to pass. These medications can be taken together. Untreated constipation can lead to a bowel blockage, so be sure to notify your healthcare team if you do not have a bowel movement for 3 or more days.
Feeling sleepy, drowsy or lightheaded may accompany the use of opioid painkillers. Some people just don't "feel like themselves" on these medications. Avoid driving or any other potentially dangerous tasks that require your concentration and a clear head until you feel normal again. Avoid alcohol or other sedatives while using these medications unless they are specifically prescribed by your doctor. Most people will begin to feel like themselves after a few days on the medications. If you continue to feel "out of it" after a couple of days, talk to your doctor about adjusting your dosages.
Slowed Breathing or Low Blood Pressure
You may experience low blood pressure or slowed breathing while taking an opioid painkiller. This usually only occurs when the dose of medication is too high or it is increased too quickly. This rarely happens to patients who have been taking opioid medications for a long time.
These side effects can also result from an overdose of opioids. If you suspect that you or someone you know has taken an overdose of opioids, call 911 immediately. If you feel extremely tired, lightheaded, dizzy, sweaty, nauseated, or short of breath, you need to see a doctor immediately. Sometimes patients who have taken too much opioid medication will be so sleepy that they can't be awakened or aroused. These side effects are emergency situations. If any of these symptoms occur, you should seek emergency medical attention.
Concerns About Addiction, Tolerance, and Dependence
Many people who are prescribed opioid pain relievers are worried that they may become addicted to these medications. This fear stems from the fact that opioid medications can cause euphoria and pleasure when used by people who are not in pain. However, when these medications are used to treat physical pain, it is extremely unlikely that patients will become addicted to them. Addiction is a psychological need for the drug that very rarely affects people who take opioids for pain control. "Feeling high" from opiates does not happen to people who take them for pain control. People often confuse withdrawal and addiction, but they are different.
Just as a person on long-term opioids stops experiencing some of the negative side effects after a few days, they may also stop getting proper pain relief after taking them for a while. This phenomenon is called tolerance. As patients develop tolerance, they will need higher doses of the opioids to get adequate levels of pain relief. Tolerance is a completely normal aspect of taking opioid painkillers, and is nothing to be concerned about. The point of using these medications is to keep pain well controlled, therefore the exact doses that any patient requires are not important as long as they can be kept comfortable. If you think you need to change the dose, always ask the provider that gave you the prescription. Do not try to change the dose on your own, as this may cause unwanted side effects.
As a person remains on regular doses of opioids, for as little as a week, their bodies will begin to adapt to the medications. This causes tolerance, but it can also cause dependence. Dependence means that the body "gets used to" the opioids. Dependence DOES NOT equal addiction. Dependence is a natural, physical phenomenon that happens to everyone on long-term opioid therapy. The only important thing to know about dependence is that once a patient becomes dependent on opioids, they will feel very sick if they stop the medication abruptly. Patients who are dependent on opioids and stop them all of the sudden will feel lousy, like they have the flu. This is called withdrawal and the symptoms related to it can start within 2 days of abruptly stopping opioids and may last up to 2 weeks. Withdrawal is preventable if you decrease the opioids slowly, generally over a week or so. The exact amount of time to wean is different based on dose, length of time on opioids, and some other individual factors. It is important to remember that dependence is normal, and happens to everyone who takes opioids for a long period of time. Talk to your provider if you have any concerns.
Chronic exposure of an unborn child to this medication could result in the child being born small and/or early, or having symptoms of withdrawal (including respiratory distress, behavioral changes and seizures) after birth. Effective birth control should be used while on this medication. Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive. You should not breast while receiving this medication as it is passed through a mother’s milk.
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