Biology 202, Spring 2005
First Web Papers
On Serendip

The common situation that comes to mind when one tries imagine a seizure is an unresponsive person writhing in convulsions on the floor. Still, there are many different types of seizures have been diagnosed through years. Although commonly associated with epilepsy, other factors which can induce seizure. result from head injuries, narcotics, medications, brain tumors, and high fever, name few. (1). Certain antidepressants, including a medication called Wellbutrin (chemical name: bupropion), have been known to cause seizures in some individuals. (5). When it comes to ingested medications, an important question to ask is, "Do the benefits of the medication outweigh the risk of a seizure?"

The system of chemical signaling between neurons or nerve cells in the brain gives clues as to why seizures occur. Neurotransmitters, or chemical signals, bind to a receptor on the neuron. These neurotransmitters alter the voltage of the cell, which changes the activity level of the neuron. (3). In order for the signal to be transmitted, enough signals must accumulate to bring the voltage of the neuron up to the "threshold of activation." Everyone has their own particular threshold of activation, which is a measure of how much stimulation it takes to make the neurons activate. (2). The threshold for each individual is determined by his or her genetic makeup, but the threshold can be changed by outside factors. Once the signal meets the particular threshold, a nerve impulse is initiated. (3). This nerve impulse travels down the axon, which is a nerve fiber that protrudes from the neuron and conducts signals to other neurons. This is also known as neuron firing. The space between the end of an axon on one neuron and the receptor on the next neuron is called the synapse. Presynaptic neurons send signals to postsynaptic neurons. (3).

The threshold of activation is similar to the seizure threshold, which is the minimum amount stimulation needed to cause a seizure. (1). Often due to genetics, some people have a low seizure threshold, so a minor stimulation may produce a seizure. Often, epileptic patients suffer from a low seizure threshold. In people with a more "normal" seizure threshold, the stimulation needs to be much more severe. (1). A person has a seizure because their neurons fire uncontrollably after being stimulated to a point at or above their seizure threshold. (1). A seizure is a change in behavior which is due to electrical activity in the brain. Some sufferers experience convulsions and unconsciousness, depending upon the type of seizure. Epilepsy is when the individual has recurrent seizures. (4).

Wellbutrin is an antidepressant which increases the levels of the neurotransmitters dopamine, serotonin, and norepinephrine. (5). Common antidepressants called SSRIs (selective serotonin reuptake inhibitors) concentrate on increasing serotonin at the synapse. Wellbutrin is different in that it is called a dopamine reuptake blocking compound because it primarily affects dopamine. (5). Reuptake is a process where neurotransmitters are released into the synapse, bind to the receptor on the receiving neuron so that it may activate, and then are sent back to the original neuron. (6). The antidepressant compounds bind to the receptor on the presynaptic neuron so that the neurotransmitter will not be transported back to the original nerve cell. Reuptake inhibitors allow the neurotransmitters to stay in the synapse longer so that they can be recognized by the postsynaptic receptor repeatedly and therefore increase their effects and levels in the synapse. (6). Since dopamine is a compound which is said to increase pleasure, it makes sense that a taking a dopamine reuptake blocking compound might make a person "feel better." (7). The problem is that if these signals are constantly firing because they are uninhibited, the seizure threshold can become lower, which can cause a seizure. (1).

The relationship between antidepressants and narcotics and their similar ability to cause seizures was surprising. Cocaine, for example, is also a dopamine reuptake blocking compound. (8). In fact, Wellbutrin has been used to gradually wean addicts off of cocaine. (10). Similarly, bupropion is also known as Zyban, which is a medication to help people stop smoking. (9). It would seem that Wellbutrin is similar to a low dosage of cocaine. Cocaine is a leading cause of seizures for the same reason that antidepressants can cause them. (9). The narcotic also raises serotonin and norepinephrine levels, though as with Wellbutrin, dopamine is the neurotransmitter that is primarily affected. (8). It makes sense logically to believe that many types of psychological medications would be comparable to narcotics because they often both have the general effect of making the user feel better. Still, it is notable that psychiatrists often don't explicitly state the similarity between narcotics and certain medications, which would be useful information in the case of Wellbutrin because it also has the some of the same adverse side effects as cocaine.

Wellbutrin is said to only cause seizures when there are complications, such as previous neurological defects, a medication overdose, or taking Wellbutrin with other drugs. (11). If we look at the basic causes of seizures, however, it is relatively easy to have a complication. The seizure threshold can be lowered by problems such as sleep deprivation, low-blood sugar levels, metabolism, anxiety, and exhaustion. (1). If combined with Wellbutrin, a seizure could result. Medication overdoses occur with Wellbutrin even when it is taken as prescribed because the brain metabolizes the medication too quickly in some people. The neurons begin firing at a rapid rate all at once which causes an overwhelming amount of electricity in the brain. SSRIs target serotonin more than dopamine, so the side effects are not the same and seizures are not as much of a risk. (11). SSRI side effects occur because this medication floods the brain with serotonin. The overabundance of serotonin interferes with the activity level of other neurotransmitters, including those which control hormones for sexual desire. (6). SSRIs are known to cause nausea, diarrhea, headache, sexual dysfunction, and dizziness. (11).

Deciding whether or not to take a medication because of its side effects is a choice that is made on an individual basis. In the case of seizures, the decision is even more important because a seizure is potentially life threatening, especially if the sufferer is driving a car at the time of the attack. When it comes to chemicals that affect the brain, patients should be informed that it is possible that compounds with similar effects might actually work in the same way. Rather than downplaying the similarity between narcotics and antidepressants, physicians should research the validity of this argument in order to help the patient to understand what it is that they are ingesting. Having experienced a seizure due to medication, I can say that for me, the benefits did not outweigh the side effects.

References

1) Behavior Modification for Epilepsy: raising the seizure threshold, website about the seizure threshold

2) Nervous System, explains the causes for seizures

3) Campbell, Neil A. and Reece, Jane. B. Biology. San Francisco: Benjamin Cummings, 2002.

4) Seizures and Epilepsy: Hope Through Research, details causes and types of seizures

5) Wellbutrin etc. (Bupropion), explains how Wellbutrin works

6) Selective serotonin reuptake inhibitor, uses of SSRIs

7) Dopamine, effects of dopamine on the brain

8) Cocaine, relationship between dopamine and cocaine

9) The Real Facts About Wellbutrin/Zyban a.k.a. Bupropion, harmful effects of Wellbutrin

10) Bupropion, uses for Wellbutrin

11) Wonderful Wellbutrin?, side effects from antidepressants


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