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Phenytoin serum level determinations may be necessary for optimal dosage adjustments (see DOSAGE AND ADMINISTRATION and CLINICAL PHARMACOLOGY sections).
DOSAGE AND ADMINISTRATION
Serum concentrations should be monitored in changing from Dilantin (extended phenytoin sodium capsules, USP) to Prompt Phenytoin Sodium Capsules, USP, and from the sodium salt to the free acid form.
Dilantin (extended phenytoin sodium capsules, USP) are formulated with the sodium salt of phenytoin. The free acid form of phenytoin is used in Dilantin-125 Suspension and Dilantin Infatabs. Because there is approximately an 8% increase in drug content with the free acid form over that of the sodium salt, dosage adjustments and serum level monitoring may be necessary when switching from a product formulated with the free acid to a product formulated with the sodium salt and vice versa.
Dosage should be individualized to provide maximum benefit. In some cases, serum blood level determinations may be necessary for optimal dosage adjustments-the clinically effective serum level is usually 10 to 20 mcg/mL. With recommended dosage, a period of seven to ten days may be required to achieve steady-state blood levels with phenytoin and changes in dosage (increase or decrease) should not be carried out at intervals shorter than seven to ten days.
Divided Daily Dosage
Patients who have received no previous treatment may be started on one 100-mg Dilantin (extended phenytoin sodium capsule, USP) three times daily and the dosage then adjusted to suit individual requirements. For most adults, the satisfactory maintenance dosage will be one capsule three to four times a day. An increase up to two capsules three times a day may be made, if necessary.
In adults, if seizure control is established with divided doses of three 100-mg Dilantin (extended phenytoin sodium capsules, USP) daily, once-a-day dosage with 300 mg of Dilantin (extended phenytoin sodium capsules, USP) may be considered. Studies comparing divided doses of 300 mg with a single daily dose of this quantity indicated absorption, peak plasma levels, biologic half-life, difference between peak and minimum values, and urinary recovery were equivalent. Once-a-day dosage offers a convenience to the individual patient or to nursing personnel for institutionalized patients and is intended to be used only for patients requiring this amount of drug daily. A major problem in motivating noncompliant patients may also be lessened when the patient can take this drug once a day. However, patients should be cautioned not to miss a dose, inadvertently.
Only Dilantin (extended phenytoin sodium capsules, USP) are recommended for once-a-day dosing. Inherent differences in dissolution characteristics and resultant absorption rates of phenytoin due to different manufacturing procedures and/or dosage forms preclude such recommendation for other phenytoin products. When a change in the dosage form or brand is prescribed, careful monitoring of phenytoin serum levels should be carried out.
Some authorities have advocated use of an oral loading dose of phenytoin in adults who require rapid steady-state serum levels and where intravenous administration is not desirable. This dosing regimen should be reserved for patients in a clinic or hospital setting where phenytoin serum levels can be closely monitored. Patients with a history of renal or liver disease should not receive the oral loading regimen.
Initially, one gram of Dilantin (extended phenytoin sodium capsules, USP) is divided into three doses (400 mg, 300 mg, 300 mg) and administered at two-hour intervals. Normal maintenance dosage is then instituted 24 hours after the loading dose, with frequent serum level determinations.
Dosing In Special Populations
Patients With Renal Or Hepatic Disease
Due to an increased fraction of unbound phenytoin in patients with renal or hepatic disease, or in those with hypoalbuminemia, the interpretation of total phenytoin plasma concentrations should be made with caution. Unbound phenytoin concentrations may be more useful in these patient populations.
Phenytoin clearance is decreased slightly in elderly patients and lower or less frequent dosing may be required.
Initially, 5 mg/kg/day in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily. A recommended daily maintenance dosage is usually 4 to 8 mg/kg. Children over 6 years old and adolescents may require the minimum adult dose (300 mg/day).
30 mg Dilantin- (extended phenytoin sodium capsule, USP)
A size 4 hemispherical Coni-Snap capsule with a white opaque body and pale pink opaque cap containing a white powder. Capsule is imprinted with black rectified radial print, “PD” on cap and “Dilantin 30 mg” on body.
100's (NDC 0071-3740-66)
100 mg Dilantin-100 mg (extended phenytoins odium capsule, USP)
Hard, filled No. 3 capsules containing a white powder. The medium orange cap having “PD” printed in black ink and the white, opaque body having “DILANTIN” over “100 mg” printed in black ink.
100's (NDC 0071-0369-24)
1,000's (NDC 0071-0369-32)
Unit Dose 100's (NDC 0071-0369-40)
Store at 20 to 25°C (68 to 77°F) [See USP Controlled Room Temperature]. Preserve in tight, light-resistant containers. Protect from moisture.
Distributed by: Parke-Davis, Division of Pfizer Inc., NY, NY 10017. Revised: Oct 2016This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 11/28/2016
Additional Dilantin Kapseals Information
- Dilantin Kapseals Drug Interactions Center: phenytoin sodium extended oral
- Dilantin Kapseals Side Effects Center
- Dilantin Kapseals Overview including Precautions
- Dilantin Kapseals FDA Approved Prescribing Information including Dosage
Dilantin Infatabs - User Reviews
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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