How Long Until Seizure Medicine Works?
How Long Does It Take for Seizure Medicines to Reach the Bloodstream?
A dose of medication will reach a peak, or maximum, level in the blood 30 minutes to 4 or 6 hours after it is taken. The time between taking the medication and reaching the peak level depends on the specific medicine and what form it is in, for example a liquid, tablets, capsule or slow-release form. Eating before a dose may also affect how long it takes to reach a peak level.
- In general, liquids are absorbed quickly.
- Medications in slow-release forms are absorbed gradually over hours and produce the steadiest levels in the blood. These slow-release forms can be taken less often, once or twice a day.
What Does "Half-Life" Mean?
A medicine's half-life is the time it takes for its level in the blood to be reduced by one-half. The half-life of each seizure medicine depends on how quickly it is broken down and gotten rid of from the body. How often a medicine should be taken depends on the drug’s half-life.
- If a medicine has a short half-life, the amount in your blood may quickly become too low to control your seizures. Medicines with short half-lives ideally should be taken several times a day. Then you can take a smaller amount each time and your blood level will stay more stable.
- Medicines with long half-lives have more stable levels over a number of hours. This allows the medicine be taken less often.
When Are Seizure Medicines Most Likely to Work?
Seizure medicines work best when the amount in your system reaches a steady state or constant amount.
- To keep this steady or constant amount, the medicine needs to be taken on a regular basis. The amount you take in needs to equal the amount your body gets rid of.
- Just because a medicine has reached a steady state doesn’t mean that it will control seizures. Only by taking the medicine for a while (usually a number of months) can you tell if the drug is going to work for you.
Is It Normal for Blood Levels of Seizure Medicines to Fluctuate?
Yes, even when someone has been taking the same medication for a long time the amount in your body will change over the course of the day. Missed doses can also be a reason for why medicine levels change. Dose-related side effects are more likely to occur at times of the highest (peak) levels, and a seizure is more likely to occur at times of the lowest (trough) levels.
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