November 1996

FORMULARY ADDITIONS

Fosphenytoin (Cerebyx ®)
500mg PE/10 ml vial
100mg PE/10 ml vial
Parke-Davis

Fosphenytoin, a prodrug that is metabolized into phenytoin after parenteral administration, is indicated for the short-term intravenous or intramuscular treatment of generalized convulsive status epilepticus and the prevention and treatment of seizures occurring during neurosurgery when other means of phenytoin are unavailable. Fosphenytoin can also be substituted for short-term oral phenytoin therapy. The safety and efficacy of fosphenytoin have not been evaluated for more than 5 days.

Adverse reactions in clinical trials have been similar to those seen with parenteral phenytoin administration, with the most serious adverse events being cardiovascular collapse and/or central nervous system depression. Higher rates of pruritus, nystagmus, pelvic pain, body pain, tongue disorder, taste perversion, and diplopia were noted for fosphenytoin compared to phenytoin. Severe irritation or extravasation rates are considerably lower with fosphenytoin compared to phenytoin.

Fosphenytoin is dosing is expressed in terms of phenytoin sodium equivalents (PE). The recommended dose of fosphenytoin is 15 to 20 PE in the treatment of status epilepticus and 10-20 PE/kg for nonemergent loading and maintenance dosing. Physicians ordering fosphenytoin should dose individuals in phenytoin equivalents (ie 15mg/kg loading dose for 100kg man should be ordered Fosphenytoin 1500mg PE).

Fosphenytoin can be administered intramuscularly and intravenously. Fosphenytoin must be diluted in either 5% dextrose or 0.9% saline solution for injection to a concentration from 1.5 to 25 mg PE/ml. Intravenous infusion rate should not exceed 150 mg PE/min, as untoward cardiovascular effects are more likely to occur at higher rates.

Fosphenytoin should be monitored the same as phenytoin. Fosphenytoin dosing should be adjusted to achieve therapeutic phenytoin plasma concentrations. Following fosphenytoin administration, it is recommended that phenytoin concentrations not be monitored until the dose of fosphenytoin is fully converted to phenytoin. Full conversion occurs within approximately 2 hours after the end of an intravenous infusion and 4 hours after an intramuscular injection.

No drugs are known to interfere with the conversion of fosphenytoin to phenytoin. The most significant drug interactions with fosphenytoin are those expected to occur with phenytoin.

Fosphenytoin will replace phenytoin for all adult patients. Phenytoin will be available for pediatric and neonate patients. Fosphenytoin carries a KUMC Cost Code Index of H.

Terbinafine (Lamisil7)
250 mg Tablets
Sandoz Pharmaceuticals

Terbinafine is an allylamine antifungal agent that is indicated for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes (tinea unguium). Terbinafine has been shown to have fungicidal in vitro activity against T. rubrum, T. mentagrophytes, E. floccosum, M. gypseum, M. nanum, T. verrucosum, C. parapsilosis, and S. brevicaulis. Against C. albicans, fungistatic activity has been demonstrated.

The most commonly reported side effects to oral terbinafine in clinical trials have been nausea, cramping, mild diarrhea, burning, abdominal pain, rash and urticaria. Other side effects have included headache, loss of taste, taste distortion and tongue discoloration. Symptomatic hepatobiliary dysfunction including cholestatic hepatitis has been rarely reported with oral terbinafine therapy. Therapy should be discontinued if a progressive skin rash occurs. Transient decreases in lymphocyte counts and severe neutropenia have also been reported with terbinafine therapy. If secondary infection appears to occur or if the neutrophil count falls below 1,000 cells/mm3, therapy should be discontinued. Terbinafine metabolism occupies 5% of the total cytochrome P-450 capacity of the liver and does not interfere with the disposition of other agents that are metabolized via this pathway. Terbinafine increases the clearance of cyclosporine by 15%. The metabolism of terbinafine is decreased by 16% with coadministration of terfenadine, 33% with coadministration of cimetidine, and 100% with coadministration of rifampin.

The recommended dose for oral terbinafine is 250mg once daily for 6 weeks in patients with fingernail infections and for 12 weeks in patients with toenail infections. Tinea pedis requires treatment for 2-6 weeks and tinea corporis and tinea capitis require treatment for 2-4 weeks. The use of terbinafine is not recommended in patients with pre-existing liver disease or renal impairment (creatinine clearance 50 ml/min). Hepatic function tests are recommended in all patients who are to receive terbinafine for more than 6 weeks Additionally, monitoring of complete blood counts is recommended in patients with known or suspected immunosuppression who are to receive terbinafine for more than 6 weeks.

Clincal studies indicate that terbinafine is more effective, has a more faovorable drug interaction profile and requires a shorter duration of therapy than griseofulvin and itraconazole for the treatment of onychomycosis.

Terbinafine carries a KUMC Cost Code Index of D.

Carbamazepine Extended Release (Tegretol XR ®)
100 mg tablets
200 mg tablets
400 mg tablets
Ciba Geigy

Carbamazepine extended release tablets are indicated for use as an anticonvulsant for the treatment of partial and generalized seizures. Carbamazepine extended release should be administered on a twice daily basis (BID) with starting doses of 200 mg BID and maximum doses of 800 mg BID. Conversion from carbamazepine immediate release tablets to extended release tablets should be based on a mg per mg conversion of the total daily dose. All carbamazepine dosing should be adjusted to the needs of the individual patient.

Changes in the KUMC Formulary since 1996-1997 publications

FORMULARY ADDITIONS

FORMULARY DELETIONS

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