Therapeutic drug monitoring of phenytoin is necessary to ensure therapeutic and nontoxic levels
. Hypoalbuminemia, renal failure, and interactions with other highly protein-bound drugs (e.g., valproic acid) alter protein binding of phenytoin.
Do you administer phenytoin on an empty stomach?
This medicine can be taken with food or on
an empty stomach
. Try to take it the same way each day, since taking this with food may change the time it takes to be absorbed. Do not take antacids or medicine for diarrhea within 2 to 3 hours of taking phenytoin.
How do you administer phenytoin?
Because of the risk of local toxicity, intravenous phenytoin should be
injected slowly directly into a large vein through a large-gauge needle or intravenous catheter
.
How effective is phenytoin?
How well does the Phenytoin work? Phenytoin is
highly effective for seizures
and is one of the most commonly used seizure medicines in North America. It is best used for partial-onset seizures, which begin in one area of the brain.
What is normal phenytoin level?
Obtain a serum phenytoin level. The therapeutic range is
10-20 mcg/mL
.
What is the side effect of phenytoin?
Side Effects
Headache, nausea, vomiting, constipation, dizziness, feeling of spinning, drowsiness, trouble sleeping
, or nervousness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. Phenytoin may cause swelling and bleeding of the gums.
How do I start phenytoin?
Phenytoin typical doses are 3–5mg/kg/day. The first dose should be
given 12–24 hours after the loading dose
. Oral or nasogastric administration should be used, whenever possible. Only use intravenous administration when these options are not feasible and where cardiac monitoring is available.
Does phenytoin require blood monitoring?
Your healthcare provider must monitor your blood to make sure you are getting the correct dose
. Too much can be toxic. Not enough leaves your seizures uncontrolled. You may have this test more often when you first start taking the medicine and then regularly throughout treatment.
Why is phenytoin given at night?
For example, if the delayed-action phenytoin is taken in the evening in place of ordinary phenytoin, it might be hoped that
it would produce by the next morning higher blood and tissue concentrations of phenytoin than would
the ordinary prepara- tion, thus reducing the risk of an early morning epileptic seizure.
How long do you take phenytoin?
- It’s usual to take phenytoin once or twice a day. …
- The most common side effects of phenytoin are headaches and feeling dizzy.
- It takes around 4 weeks for phenytoin to work.
- If you have epilepsy, it’s best to stay on the same brand of phenytoin, as other brands may not work as well for you.
What happens if you take too much phenytoin?
An overdose of phenytoin can be fatal.
Overdose symptoms may include
twitching eye movements
, slurred speech, loss of balance, tremor, muscle stiffness or weakness, nausea, vomiting, feeling light-headed, fainting, and slow or shallow breathing. Avoid drinking alcohol while you are taking phenytoin.
What is normal free phenytoin level?
The reference range of free phenytoin is
1-2.5 μg/mL
. In patients with renal failure associated with hypoalbuminemia, free phenytoin levels may be more accurate than total phenytoin levels. However, the Sheiner-Tozer formula (below) can be used to correct the phenytoin level.
How do I raise my phenytoin level?
level. Here is a practical guide16 for incremen- tally increasing the phenytoin maintenance regimen (at steady state) for an adult: • serum level <7 μg/mL,
increase daily mainte- nance dose by 100 mg
• serum level of 7–11 μg/mL, increase by 50 mg • serum level ≥12 μg/mL, increase by only 30 mg.
What is phenytoin level test?
The phenytoin test is
ordered to measure and monitor the amount of phenytoin in the blood and to determine whether drug concentrations are in the therapeutic range
. It may be ordered every few days when a patient first begins taking phenytoin to help adjust the dose to the desired blood level.
What type of seizures does phenytoin treat?
Phenytoin is effective for treating
generalized tonic-clonic seizures
, partial seizures with or without generalization, and convulsive status epilepticus.
How long does phenytoin stay in your system?
The plasma half-life in man after oral administration of phenytoin averages 22 hours, with a range of
7 to 42 hours
. Steady-state therapeutic levels are achieved at least 7 to 10 days (5–7 half- lives) after initiation of therapy with recommended doses of 300 mg/day.
