If anticonvulsant levels are very low, supplemental doses may be given and the patient restarted on his or her regular regimen. Without a loading dose, the patient may not achieve anticonvulsant effects for two days to three weeks (see Table... .224-5). An oral loading-dose of phenytoin (usually 18 mg/kg po, that is often divided into 3 doses given q2h) will achieve therapeutic serum concentrations in 2 to 24 h. Alternatively, the same loading dose of IV phenytoin (no faster than 50 mg/min) achieves anticonvulsant effects in 1 to 2 h. Carbamazepine can be loaded using the oral suspension at a dose of 8 mg/kg.
If anticonvulsant levels are adequate and the patient has had a single attack, specific treatment may not be needed if the pattern and frequency of occurrence falls within the expected range for the patient. Even well-controlled patients may have occasional breakthrough seizures. Any precipitants that have lowered the seizure threshold should be identified. If there has been a recent change in the frequency or pattern of breakthrough seizures, a change in, or adjustment of, medication may be needed. These include factors such as infection, sleep deprivation, stress, or injury. The primary care physician or neurologist should make this decision. If a medication's maintenance dose is increased, only very small increments should be made, and follow-up within one to three days should be provided, because even small dose changes may result in dramatic increases in serum levels. If the problem is noncompliance or missed medication, the patient's primary care physician or neurologist should be made aware of the situation and participate in decision making.
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