When you are considering or starting a new seizure medicine, your doctor will discuss some basic information with you. When you get the prescription filled, you will probably receive additional written information. This may be just a brief summary, or you may receive a very detailed "package insert" filled with information that is approved by the U.S. Food and Drug Administration (FDA) based on studies (clinical trials) in which the medication is given to patients. Such package inserts are available for all prescription medications approved by the FDA. Similar information is available for nonprescription medicines and for some herbal medicines and dietary supplements.
The package inserts for thousands of prescription medicines are compiled into a reference book called the Physicians' Desk Reference, better known as "the PDR." This book should be available in the reference section of your library. The information also can be accessed online if you pay a subscription fee.
The information in a package insert (or in the PDR) follows a standard format for every medication. After some identifying information such as the brand name and generic name of the product, the following sections appear:
Package inserts for some medicines also include a section on Drug Abuse and Dependence, if those are potential problems, and some begin with "Box Warnings," which highlight especially serious (often life-threatening) adverse reactions that have been reported.
Here is what you can expect to find in each section:
This section gives the chemical name of the drug and a structural diagram showing the various atoms and molecules that comprise it. It tells whether it is in tablet form, capsules, liquid, etc., and how it should be given-by mouth (oral administration), by injection, by adding it to a solution being given via an intravenous (IV) line (parenteral administration), and so forth. It also lists all inactive ingredients such as fillers, artificial colors, or flavorings. If you have food sensitivities, this is where you can check for the presence of the substances that cause you problems.
For most people who are not health care professionals, a lot of the information in this section is difficult to understand. You'll see words like "Pharmacodynamics," "Pharmacokinetics" and "Bioavailability." Basically, this section tells how the medicine works in the body, how it is absorbed and eliminated, and what its effects are likely to be at various concentrations. It also tells whether studies in different groups of people found any differences in how it works for children, elderly people, women, or people of different races. Sometimes this section will also include the results of studies into how well the medicine worked for different purposes. For instance, Depakote (valproate) is primarily a seizure medicine but it can also be used for bipolar disorder or migraine, and this section of its package insert includes results of studies of its use in all three disorders.
If you have a special problem like kidney or liver disease, this is one of the sections your doctor will consult while deciding whether to prescribe this type of medicine for you, and if so, how much to give and when.
This section lists the uses (indications) for which the drug has been FDA-approved. If your type of epilepsy is not listed, don't be alarmed. It is very common (and perfectly legal) for doctors to prescribe medicines for purposes that are not named in this section (so-called "off-label" uses). The conditions that are named are those for which adequate research studies were performed before the medication was approved. Less common types of epilepsy or seizures that affect children are much less likely to have been studied. Since studies in children are performed less often, many uses of seizure medicines for children are "off-label." The doctor will review other studies, experiences with other patients, and the opinions of experts in the field, and then will use his or her own professional judgment in deciding whether this medicine is likely to help you.
Some seizure medicines are also used for conditions other than epilepsy. For example, Neurontin (gabapentin) is often used to treat certain kinds of pain, and Depakote (valproate) is used for bipolar disorder or migraine. So if you need treatment for some other condition besides epilepsy, your doctor may consider whether the same medication could help with both things.
If indications are the situations in which the medicine should be used, contraindications are situations that advise against its use -- that is, this section lists situations in which it should not be used. For instance, a medicine should not be prescribed for someone who has had an allergic reaction to the same medication or one that's similar, or for someone who is taking another medicine that interacts with it in a harmful way.
This section also may warn doctors not to prescribe the medicine for people with certain medical conditions because they are at greater risk of dangerous side effects. For example, the package insert for Depakote warns that it should not be used by people with liver disease. If you have a significant medical disorder, this is the place to find out whether it's likely to cause a problem if you take this medicine.
This section discusses serious side effects that may occur in people who take this medicine. If especially severe or life-threatening problems have been found, there may be a "Box Warning" on the first page of the package insert. As the name suggests, this information is prominently displayed using capital letters surrounded by a black box so it will not be overlooked. You should pay attention to these warnings so you will recognize any symptoms that could suggest a serious problem, but you should not be overly alarmed. It is quite unlikely that you will experience any of the conditions covered by Box Warnings or by the Warnings section later in the package insert. Many widely used medicines (such as Tegretol (carbamazepine) and Depakote) have Box Warnings and very few people are severely harmed.
Before you start taking a seizure medicine with Warnings that might pertain to you, your doctor is likely to explain what the Warnings mean and tell you what you should watch for so that any problems can be caught early.
Included in the Warnings section for many seizure medicines is a discussion of possible problems if the medication is taken during pregnancy. These are worth reviewing with your doctor if you are considering pregnancy, but most women have healthy babies regardless of which medicine they use. Good seizure control usually is the most important consideration.
The Precautions section advises how to use the medication most safely and effectively. It alerts the doctor about types of patients who need close observation and offers guidelines about any laboratory tests that should be performed before the medicine is taken or during the time it is in use. This section may list activities (such as driving) that require special caution while the medicine is being used. Sometimes the information on pregnancy appears in this section rather than in Warnings.
One of the most important parts of this section lists Drug Interactions—the effects that this medicine may have on other prescription or over-the-counter medicines you may be taking, or the effects of the other medicines on this one. If your doctor tells you that the dosage of another medicine you're taking must be changed when you begin a new medication, it's probably because of an interaction listed in this section. This section also might warn that you shouldn't take this medicine with a particular food or other product (such as an antacid). It's a good idea to skim this section to see if it lists any medicines or other products that you use regularly. (Note that the generic names of medicines are used, so that's what you should look for instead of the brand name. For instance, you may find "phenytoin" but you will not find "Dilantin.") If you find something and you're not sure what that means to you, contact your doctor's office or talk to your pharmacist.
The Precautions section also may tell what is known about the use of this medicine by nursing mothers, children ("Pediatric Use"), and older people ("Geriatric Use"). Sometimes it may just say that not enough information is available. This does not mean that such use is unsafe, just that not enough research studies have been done.
This section lists all the side effects that were reported in people who took this medicine while it was being tested. These effects are usually grouped according to the body system affected and perhaps also by how many people reported each one.
It can be hard to sort out which of the side effects on these lists you really need to be concerned about. You probably shouldn't be bothered about ones listed as rare or infrequent unless they're also discussed in the Warnings. Even "frequent" ones may have happened only a little more often in the people who took the medicine than in the people who took an inactive placebo instead. Some package inserts include tables that show these numbers, which can be interesting but also overwhelming. If you tend to have problems with one body system (such as your lungs or digestion), you may be particularly interested in seeing how many people had problems in that area.
These lists of "adverse events" can look frightening because they include so many problems, ranging from trivial to life-threatening. The thing to remember is that this section lists everything that happened to hundreds or thousands of people (and sometimes also animals) regardless of whether it actually had any connection to the medicine. For instance, if you were a part of one of these studies and you caught a cold, you would tell the doctor about it and the study results would list "respiratory infection" (that is, a cold) as one of the adverse effects. Common sense tells us that most people get a cold from time to time, so this particular cold probably was not a result of the medicine you were taking, but it appears on the list anyway.
You may experience some of the side effects on the list or none at all. Even the effects listed as being most frequent do not affect everyone who takes the medicine. A further complication is that often seizure medicines are tested in combination with other seizure medicines, so if you are not taking the same combination, the effects on you may be different.
Your doctor probably will mention some of the side effects that you should watch for, but every person is different and it is impossible to tell in advance what you will experience. Many side effects that are troublesome during the first days or weeks that you take the medicine may disappear later.
This section tells whether this medicine could be abused or cause psychological or physical dependence. The package inserts for most seizure medicines say that there is no evidence of abuse potential or dependence, or that it has not been evaluated in humans. Seizure medicines that are in the barbiturate or benzodiazepine groups (such as phenobarbital, Mysoline (primidone), and Klonopin (clonazepam)) can cause dependence, however.
If you have a history of dependence on drugs you may want to check this section to see whether this medicine could cause a problem for you. Dependency will also be a consideration if you have been taking a dependency-causing medicine for a while, regardless of your history. If you want to stop taking it, the dosage will have to be tapered very slowly.
This section tells what the results of a large overdose of the medicine are likely to be and how they should be treated. This kind of information is mainly useful to medical personnel. If you suspect an overdose of medication, you should contact a poison control center or emergency room right away.
This section gives the recommended dosages of the medicine. Usually it will suggest an initial dosage and recommend the amount and timing of any increases that will be needed to reach an effective dosage without excessive side effects. Many times your doctor will suggest that you start the medicine at a lower dose than given here and increase the dosage more slowly to lessen the chance of side effects even more.
If the medicine is indicated for more than one use (such as for epilepsy and for migraine, or for different types of seizures), you may see separate sections for each use. Separate information also may be given about dosages for children, older people, or those with certain medical problems.
If your doctor has prescribed a regimen for you that is considerably different from what you see in this section, you might ask for an explanation, but you should continue to follow your doctor's plan. Factors specific to you, such as health problems or other medications, may mean that you need a different dosage.
This section also gives storage instructions. This is where you find out whether to keep the liquid form in the refrigerator or not. It also tells whether pills are particularly vulnerable to damage from heat, light, or moisture. Usually there's a recommendation against exposing the medicine to temperatures over 30ºC (86ºF), for instance, so if you pick up your prescription from the pharmacy on a hot day, don't leave it in the car while you run other errands!
It's a good idea to review the package insert for any new medicine and to look at it again if anything about your health changes. If it raises any questions in your mind, contact your doctor or nurse for an explanation. You may even avoid a serious problem if it causes you to recall some aspect of your medical history that you haven't shared with your doctor.
Topic Editor: Steven C. Schachter, M.D.