Topiramate — commonly known as topamax in Canada and the United States — was approved for use as a treatment for epilepsy in 1995. But in 2004, the American Food and Drug Administration approved the drug for use in treating migraines.
Since then, it has become the world's best-selling migraine prevention medication. More than four million people have used it.
What is topamax?
It is an anticonvulsant drug designed to suppress the rapid and excessive firing of neurons that start some types of epileptic seizures. The drug will not cure epilepsy but should help control seizures for as long as it is taken.
Topamax also helps prevent the onset of migraines, possibly in a similar way that it prevents epileptic seizures from starting. It is not used to treat migraines that have already started. The drug's manufacturer — Janssen-Ortho — says people who take topamax may still suffer some migraine headaches but the frequency will be far less than without the drug.
It has not been approved to treat migraines in children.
How is it used?
Topamax comes in tablet and sprinkle capsule form. It is usually taken twice a day — once in the morning and once in the evening. It is supposed to be taken at around the same time every day.
The tablets should never be broken — they have a bitter taste and quickly lose their effectiveness when broken, crushed or split.
Sprinkle capsules can be swallowed whole or their contents can be sprinkled on a small amount of food. It's best to swallow the mixture without chewing it.
Are there other conditions for which topamax is prescribed?
Topamax is approved only for treatment of epilepsy and migraines. However, it has also been investigated as a treatment for obesity, especially binge eating as well as alcoholism and for some psychiatric conditions like bipolar disorder. A study in the Annals of General Psychiatry found that topamax does not help in the treatment of acute mania, but may have a place in the treatment of binge eating, alcohol dependence and possibly bipolar disorder.
What are the drug's side-effects?
Among the most common side-effects is a change in taste. For instance, carbonated beverages — especially diet soft drinks and beer — can taste particularly bad.
Topamax may cause some people to have blurred vision, double vision, clumsiness or unsteadiness, or to become dizzy, drowsy or have trouble in thinking. It can also add to the effects of alcohol and some drugs like antihistamines that make you drowsy or less alert.
In September 2001, Janssen-Ortho issued a warning that topamax is associated with acute myopia and secondary angle closure glaucoma. Up to that point, there had been 23 cases — including one in Canada — in people on topamax. Symptoms typically appeared in the first month of topamax therapy.
The drug may also affect your ability to sweat, which can cause your body temperature to increase. If your body does overheat during exercise or hot weather while you are on the medicine, you could be at increased risk for heat stroke.
There's also the possibility that — in conjunction with other factors — topamax may lead to a condition known as metabolic acidosis or make it worse. The condition is caused when there is too much acid in the blood. The consequences can be serious and can include coma or death.
In 2004, the drug's manufacturer issued a warning that topamax is associated with metabolic acidosis.
What are the symptoms of a topamax overdose?
There are many and they vary from person to person. They can include seizures, drowsiness, speech problems, blurred vision, double vision, trouble thinking, tiredness, loss of co-ordination, loss of consciousness, coma, fainting, dizziness, stomach pain, upset stomach, vomiting and excessive hunger.
There have been 254 reports of adverse reactions involving topamax to the Canadian Adverse Drug Reaction Monitoring Program database. In three of those cases, topamax was citied as possibly contributing to the deaths of the individuals.
What do I do if I suspect I'm suffering from a topamax overdose?
Call your local poison control centre or go directly to the emergency department of your local hospital. There is no specific antidote for a topamax overdose. Treatment depends on your symptoms.
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