Ziprasidone

7 DRUG INTERACTIONS Drug-drug interactions can be pharmacodynamic (combined pharmacologic effects) or pharmacokinetic (alteration of plasma levels). The risks of using ziprasidone in combination with other drugs have been evaluated as described below. All interactions studies have been conducted with oral ziprasidone. Based upon the pharmacodynamic and pharmacokinetic profile of ziprasidone, possible interactions could be anticipated: • Ziprasidone should not be used in combination with other drugs that have demonstrated QT prolongation. ( 4.1 , 7.3 ) • The absorption of ziprasidone is increased up to two-fold in the presence of food. ( 7.10 ) • The full prescribing information contains additional drug interactions. (7) . 7.1 Metabolic Pathway Approximately two-thirds of ziprasidone is metabolized via a combination of chemical reduction by glutathione and enzymatic reduction by aldehyde oxidase. There are no known clinically relevant inhibitors or inducers of aldehyde oxidase. Less than one-third of ziprasidone metabolic clearance is mediated by cytochrome P450 catalyzed oxidation. 7.2 In Vitro Studies An in vitro enzyme inhibition study utilizing human liver microsomes showed that ziprasidone had little inhibitory effect on CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4, and thus would not likely interfere with the metabolism of drugs primarily metabolized by these enzymes. There is little potential for drug interactions with ziprasidone due to displacement [see Clinical Pharmacology (12.3) ]. 7.3 Pharmacodynamic Interactions • Ziprasidone should not be used with any drug that prolongs the QT interval [see Contraindications (4.1) ]. • Given the primary CNS effects of ziprasidone, caution should be used when it is taken in combination with other centrally acting drugs. • Because of its potential for inducing hypotension, ziprasidone may enhance the effects of certain antihypertensive agents. • Ziprasidone may antagonize the effects of levodopa and dopamine agonists. • Risk of serotonin syndrome with concomitant therapy with other serotonergic drugs such as SNRIs, SSRIs, triptans, tricyclic antidepressants, opioids, lithium, tryptophan, buspirone, amphetamines, and St. John’s Wort [see Contraindications ( 4.3 ), Warnings and Precautions ( 5.4 ), Adverse Reactions ( 6.2 )]. 7.4 Pharmacokinetic Interactions Carbamazepine Carbamazepine is an inducer of CYP3A4; administration of 200 mg twice daily for 21 days resulted in a decrease of approximately 35% in the AUC of ziprasidone. This effect may be greater when higher doses of carbamazepine are administered. Ketoconazole Ketoconazole, a potent inhibitor of CYP3A4, at a dose of 400 mg QD for 5 days, increased the AUC and C max of ziprasidone by about 35 to 40%. Other inhibitors of CYP3A4 would be expected to have similar effects. Cimetidine Cimetidine at a dose of 800 mg QD for 2 days did not affect ziprasidone pharmacokinetics. Antacid The co-administration of 30 mL of Maalox® with ziprasidone did not affect the pharmacokinetics of ziprasidone. 7.5 Lithium Ziprasidone at a dose of 40 mg twice daily administered concomitantly with lithium at a dose of 450 mg twice daily for 7 days did not affect the steady-state level or renal clearance of lithium. Ziprasidone dosed adjunctively to lithium in a maintenance trial of bipolar patients did not affect mean therapeutic lithium levels. 7.6 Oral Contraceptives In vivo studies have revealed no effect of ziprasidone on the pharmacokinetics of estrogen or progesterone components. Ziprasidone at a dose of 20 mg twice daily did not affect the pharmacokinetics of concomitantly administered oral contraceptives, ethinyl estradiol (0.03 mg) and levonorgestrel (0.15 mg). 7.7 Dextromethorphan Consistent with in vitro results, a study in normal healthy volunteers showed that ziprasidone did not alter the metabolism of dextromethorphan, a CYP2D6 model substrate, to its major metabolite, dextrorphan. There was no statistically significant change in the urinary dextromethorphan/dextrorphan ratio. 7.8 Valproate A pharmacokinetic interaction of ziprasidone with valproate is unlikely due to the lack of common metabolic pathways for the two drugs. Ziprasidone dosed adjunctively to valproate in a maintenance trial of bipolar patients did not affect mean therapeutic valproate levels. 7.9 Other Concomitant Drug Therapy Population pharmacokinetic analysis of schizophrenic patients enrolled in controlled clinical trials has not revealed evidence of any clinically significant pharmacokinetic interactions with benztropine, propranolol, or lorazepam. 7.10 Food Interaction The absolute bioavailability of a 20 mg dose under fed conditions is approximately 60%. The absorption of ziprasidone is increased up to two-fold in the presence of food [ see Clinical Pharmacology (12.3) ].

Indicated for treatment of schizophrenia in adults; acute treatment of manic or mixed episodes associated with bipolar I disorder; maintenance treatment of bipolar I disorder as an adjunct to lithium or valproate; and, in the intramuscular formulation, acute agitation in patients with schizophrenia.

2 DOSAGE AND ADMINISTRATION • Administer capsules orally with food. Do not open, crush, or chew. ( 2.1 ) • Schizophrenia: Initiate at 20 mg twice daily. Daily dosage may be adjusted up to 80 mg twice daily. Dose adjustments should occur at intervals of not less than 2 days. Safety and efficacy has been demonstrated in doses up to 100 mg twice daily. The lowest effective dose should be used. ( 2.2 ) • Acute treatment of manic/mixed episodes of bipolar I disorder: Initiate at 40 mg twice daily. Increase to 60 mg or 80 mg twice daily on day 2 of treatment. Subsequent dose adjustments should be based on tolerability and efficacy within the range of 40 to 80 mg twice daily. ( 2.3 ) • Maintenance treatment of bipolar I disorder as an adjunct to lithium or valproate: Continue treatment at the same dose on which the patient was initially stabilized, within the range of 40 to 80 mg twice daily. ( 2.3 ) 2.1 Administration Information for Ziprasidone Capsules Administer ziprasidone capsules orally with food. Swallow capsules whole, do not open, crush, or chew the capsules. 2.2 Schizophrenia Dose Selection Ziprasidone capsules should be administered at an initial daily dose of 20 mg twice daily with food. In some patients, daily dosage may subsequently be adjusted on the basis of individual clinical status up to 80 mg twice daily. Dosage adjustments, if indicated, should generally occur at intervals of not less than 2 days, as steady-state is achieved within 1 to 3 days. In order to ensure use of the lowest effective dose, patients should ordinarily be observed for improvement for several weeks before upward dosage adjustment. Efficacy in schizophrenia was demonstrated in a dose range of 20 mg to 100 mg twice daily in short-term, placebo-controlled clinical trials. There were trends toward dose response within the range of 20 mg to 80 mg twice daily, but results were not consistent. An increase to a dose greater than 80 mg twice daily is not generally recommended. The safety of doses above 100 mg twice daily has not been systematically evaluated in clinical trials [see Clinical Studies (14.1) ]. Maintenance Treatment While there is no body of evidence available to answer the question of how long a patient treated with ziprasidone should remain on it, a maintenance study in patients who had been symptomatically stable and then randomized to continue ziprasidone or switch to placebo demonstrated a delay in time to relapse for patients receiving ziprasidone capsules [see Clinical Studies (14.1) ]. No additional benefit was demonstrated for doses above 20 mg twice daily. Patients should be periodically reassessed to determine the need for maintenance treatment. 2.3 Bipolar I Disorder (Acute Mixed or Manic Episodes and Maintenance Treatment as an Adjunct to Lithium or Valproate) Acute Treatment of Manic or Mixed Episodes In adults oral ziprasidone should be administered at an initial daily dose of 40 mg twice daily with food. The dose may then be increased to 60 mg or 80 mg twice daily on the second day of treatment and subsequently adjusted on the basis of tolerance and efficacy within the range 40 mg to 80 mg twice daily. In the flexible-dose clinical trials, the mean daily dose administered was approximately 120 mg [see Clinical Studies ( 14.2 ) ]. Maintenance Treatment (as an adjunct to lithium or valproate) Continue treatment at the same dose on which the patient was initially stabilized, within the range of 40 mg to 80 mg twice daily with food. Patients should be periodically reassessed to determine the need for maintenance treatment [see Clinical Studies ( 14.2 )] . 2.5 Switching Patients to or from a Monoamine Oxidase Inhibitor (MAOI) Antidepressant At least 14 days must elapse between discontinuation of an MAOI (intended to treat psychiatric disorders) and initiation of therapy with ziprasidone capsules. In addition, at least 3 days should be allowed after stopping ziprasidone capsules before starting an MAOI intended to treat psychiatric disorders [see Contraindications ( 4.3 ), Warnings and Precautions (5.2) , and Drug Interactions (7.1 )].

In schizophrenia trials, the most common adverse reaction was "somnolence" (14% vs. 7% placebo) along with respiratory tract infection (8% vs. 3%). In bipolar mania trials, somnolence (31% vs. 12% placebo) and extrapyramidal symptoms (31% vs. 12%) were most common. With intramuscular administration, headache, nausea, and somnolence were frequently reported.