Celexa citalopram 40 mg Tablet, Film Coated, 100-count — NDC 0456-4040-01 (Billing 00456-4040-01)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action The mechanism of action of citalopram is unclear, but is presumed to be related to potentiation of serotonergic activity in the central nervous system (CNS) resulting from its inhibition of CNS neuronal reuptake of serotonin (5-HT).

12.2Pharmacodynamics In vitro and in vivo studies in animals suggest that citalopram is a selective serotonin reuptake inhibitor (SSRI) with minimal effects on norepinephrine (NE) and dopamine (DA) neuronal reuptake. Citalopram has no or very low affinity for 5-HT 1A , 5-HT 2A , dopamine D 1 and D 2 , α 1 -, α 2 -, and β-adrenergic, histamine H 1 , gamma aminobutyric acid (GABA), muscarinic cholinergic, and benzodiazepine receptors. Cardiac Electrophysiology Individually corrected QTc (QTcNi) interval was evaluated in a randomized, placebo and active (moxifloxacin 400 mg) controlled cross-over, escalating multiple-dose study in 119 healthy subjects.

The maximum mean (upper bound of the 95% one-sided confidence interval) difference from placebo were 8.5 (10.8) and 18.5 (21.0) msec for 20 mg and 60 mg (1.5 times the maximum recommended dosage) citalopram, respectively. Based on the established exposure-response relationship, the predicted QTcNi change from placebo (upper bound of the 95% one-sided confidence interval) under the Cmax for the dose of 40 mg is 12.6 (14.3) msec [see Warnings and Precautions ( 5.2 )] .

12.3Pharmacokinetics The single- and multiple-dose pharmacokinetics of citalopram are linear and dose-proportional in a dose range of 10 to 40 mg/day. Biotransformation of citalopram is mainly hepatic, with a mean terminal half-life of about 35 hours. With once daily dosing, steady state plasma concentrations are achieved within approximately one week.

At steady state, the extent of accumulation of citalopram in plasma, based on the half-life, is expected to be 2.5 times the plasma concentrations observed after a single dose. Absorption Following a single oral dose (40 mg tablet) of citalopram, peak blood levels occur at about 4 hours. The absolute bioavailability of citalopram was about 80% relative to an intravenous dose, and absorption is not affected by food.

Distribution The volume of distribution of citalopram is about 12 L/kg and the binding of citalopram (CT), demethylcitalopram (DCT) and didemethylcitalopram (DDCT) to human plasma proteins is about 80%. Elimi nation Metabolism Citalopram is metabolized to demethylcitalopram (DCT), didemethylcitalopram (DDCT), citalopram-N-oxide, and a deaminated propionic acid derivative. In humans, unchanged citalopram is the predominant compound in plasma.

At steady state, the concentrations of citalopram's metabolites, DCT and DDCT, in plasma are approximately one-half and one-tenth, respectively, that of the parent drug. In vitro studies show that citalopram is at least 8 times more potent than its metabolites in the inhibition of serotonin reuptake, suggesting that the metabolites evaluated do not likely contribute significantly to the antidepressant actions of citalopram. In vitro studies using human liver microsomes indicated that CYP3A4 and CYP2C19 are the primary isozymes involved in the N-demethylation of citalopram.

Excretion Following intravenous administrations of citalopram, the fraction of drug recovered in the urine as citalopram and DCT was about 10% and 5%, respectively. The systemic clearance of citalopram was 330 mL/min, with approximately 20% of that due to renal clearance. Specific Populations Geriatric Patients Citalopram pharmacokinetics in subjects ≥ 60 years of age were compared to younger subjects in two normal volunteer studies.

In a single-dose study, citalopram AUC and half-life were increased in the subjects ≥ 60 years old by 30% and 50%, respectively, whereas in a multiple-dose study they were increased by 23% and 30%, respectively [see Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.2 ), Use in Specific Populations ( 8.5 )] . Male and Female Patient… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action The mechanism of action of citalopram is unclear, but is presumed to be related to potentiation of serotonergic activity in the central nervous system (CNS) resulting from its inhibition of CNS neuronal reuptake of serotonin (5-HT).

12.3Pharmacokinetics The single- and multiple-dose pharmacokinetics of citalopram are linear and dose-proportional in a dose range of 10 to 40 mg/day. Biotransformation of citalopram is mainly hepatic, with a mean terminal half-life of about 35 hours. With once daily dosing, steady state plasma concentrations are achieved within approximately one week.

At steady state, the extent of accumulation of citalopram in plasma, based on the half-life, is expected to be 2.5 times the plasma concentrations observed after a single dose. Absorption Following a single oral dose (40 mg tablet) of citalopram, peak blood levels occur at about 4 hours. The absolute bioavailability of citalopram was about 80% relative to an intravenous dose, and absorption is not affected by food.

Distribution The volume of distribution of citalopram is about 12 L/kg and the binding of citalopram (CT), demethylcitalopram (DCT) and didemethylcitalopram (DDCT) to human plasma proteins is about 80%. Elimi nation Metabolism Citalopram is metabolized to demethylcitalopram (DCT), didemethylcitalopram (DDCT), citalopram-N-oxide, and a deaminated propionic acid derivative. In humans, unchanged citalopram is the predominant compound in plasma.

At steady state, the concentrations of citalopram's metabolites, DCT and DDCT, in plasma are approximately one-half and one-tenth, respectively, that of the parent drug. In vitro studies show that citalopram is at least 8 times more potent than its metabolites in the inhibition of serotonin reuptake, suggesting that the metabolites evaluated do not likely contribute significantly to the antidepressant actions of citalopram. In vitro studies using human liver microsomes indicated that CYP3A4 and CYP2C19 are the primary isozymes involved in the N-demethylation of citalopram.

Excretion Following intravenous administrations of citalopram, the fraction of drug recovered in the urine as citalopram and DCT was about 10% and 5%, respectively. The systemic clearance of citalopram was 330 mL/min, with approximately 20% of that due to renal clearance. Specific Populations Geriatric Patients Citalopram pharmacokinetics in subjects ≥ 60 years of age were compared to younger subjects in two normal volunteer studies.

In a single-dose study, citalopram AUC and half-life were increased in the subjects ≥ 60 years old by 30% and 50%, respectively, whereas in a multiple-dose study they were increased by 23% and 30%, respectively [see Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.2 ), Use in Specific Populations ( 8.5 )] . Male and Female Patients In three pharmacokinetic studies (total N=32), citalopram AUC in women was one and a half to two times that in men. This difference was not observed in five other pharmacokinetic studies (total N=114).

In clinical studies, no differences in steady state serum citalopram levels were seen between men (N=237) and women (N=388). There were no gender differences in the pharmacokinetics of DCT and DDCT. Patients with Hepatic Impairment Citalopram oral clearance was reduced by 37% and half-life was doubled in patients with reduced hepatic function compared to normal subjects [see Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.2 ), Use in Specific Populations ( 8.6 )] .

Patients with Renal Impairment In patients with mild to moderate renal impairment, oral clearance of citalopram was reduced by 17% compared to normal subjects. No adjustment of dosage for such patients is recommended. No information is available about the pharmacokinetics of citalopram in patients with severe renal impairment (creatinine clearance < 20 mL/min).

CYP2C19 poor metabolizers In CYP2C19 poor metabolizers, citalopram steady state Cmax and AUC was increased by 68% and 107%, respectively [see Dosage and Administration ( 2.3 ),Warnings and Precautions ( 5.2 )] . CYP2D6 poor metabolizers Citalopram steady state levels were not significantly different in poor metabolizers and extensive metabolizers of CYP2D6.… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics In vitro and in vivo studies in animals suggest that citalopram is a selective serotonin reuptake inhibitor (SSRI) with minimal effects on norepinephrine (NE) and dopamine (DA) neuronal reuptake. Citalopram has no or very low affinity for 5-HT 1A , 5-HT 2A , dopamine D 1 and D 2 , α 1 -, α 2 -, and β-adrenergic, histamine H 1 , gamma aminobutyric acid (GABA), muscarinic cholinergic, and benzodiazepine receptors. Cardiac Electrophysiology Individually corrected QTc (QTcNi) interval was evaluated in a randomized, placebo and active (moxifloxacin 400 mg) controlled cross-over, escalating multiple-dose study in 119 healthy subjects.

The maximum mean (upper bound of the 95% one-sided confidence interval) difference from placebo were 8.5 (10.8) and 18.5 (21.0) msec for 20 mg and 60 mg (1.5 times the maximum recommended dosage) citalopram, respectively. Based on the established exposure-response relationship, the predicted QTcNi change from placebo (upper bound of the 95% one-sided confidence interval) under the Cmax for the dose of 40 mg is 12.6 (14.3) msec [see Warnings and Precautions ( 5.2 )] .

14 CLINICAL STUDIES The efficacy of CELEXA as a treatment for major depressive disorder was established in two placebo-controlled studies (of 4 to 6 weeks duration) in adult outpatients (ages 18-66) meeting DSM-III or DSM-III-R criteria for major depressive disorder (MDD) (Studies 1 and 2). Study 1, a 6-week trial in which patients received fixed CELEXA doses of 10 mg, 20 mg, 40 mg, and 60 mg daily, showed that CELEXA 40 daily and 60 mg daily (1.5 times the maximum recommended daily dosage) was effective as measured by the Hamilton Depression Rating Scale (HAMD) total score, the primary efficacy endpoint.

The HAMD-17 is a 17-item, clinician-rated scale used to assess severity of depressive symptoms. Scores on the HAMD-17 range from 0 to 52, with higher scores indicating more severe depression. This study showed no clear effect of the 10 mg and 20 mg daily doses, and the 60 mg daily dose was not more effective than the 40 mg daily dose.

Due to the risk of QTc prolongation and ventricular arrhythmias, the maximum recommended dosage of CELEXA is 40 mg once daily. In study 2, a 4-week, placebo-controlled trial in patients with MDD, the initial dose was 20 mg daily, followed by titration to the maximum tolerated dose or a maximum dose of 80 mg daily (2 times the maximum recommended daily dosage). Patients treated with CELEXA showed statistically significantly greater improvement than placebo patients on the HAMD total score, the primary efficacy endpoint.

In three additional placebo-controlled trials in patients with MDD, the difference in response to treatment between patients receiving CELEXA and patients receiving placebo was not statistically significant. In two long-term studies, patients with MDD who had responded to CELEXA during an initial 6 or 8 weeks of acute treatment were randomized to continuation of CELEXA or placebo. In one study, patients received fixed doses of CELEXA 20 mg or 40 mg daily and in the second study, patients received flexible doses of CELEXA 20 mg daily to 60 mg daily (1.5 times the maximum recommended daily dosage).

In both studies, patients receiving continued CELEXA treatment experienced statistically significantly lower relapse rates over the subsequent 6 months compared to those receiving placebo. In the fixed-dose study, the decreased rate of depression relapse was similar in patients receiving 20 mg or 40 mg daily of CELEXA. Due to the risk of QTc prolongation and ventricular arrhythmias, the maximum recommended dosage of CELEXA is 40 mg once daily.

Analyses of the relationship between treatment outcome and age, gender, and race did not suggest any differential responsiveness on the basis of these patient characteristics.

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis Citalopram increased the incidence of small intestine carcinoma in rats treated for 24 months at doses of 8 and 24 mg/kg/day in the diet, which are approximately 2 and 6 times the Maximum Recommended Human Dose (MRHD) of 40 mg, respectively, based on mg/m 2 body surface area. A no-effect level (NOEL) for this finding was not established. Citalopram did not increase the incidence of tumors in mice treated for 18 months at doses up 240 mg/kg/day in the diet, which is approximately 30 times the MRDH of 40 mg based on mg/m 2 body surface area.

Mutagenesis Citalopram was mutagenic in the in vitro bacterial reverse mutation assay (Ames test) in 2 of 5 bacterial strains (Salmonella TA98 and TA1537) in the absence of metabolic activation. It was clastogenic in the in vitro Chinese hamster lung cell assay for chromosomal aberrations in the presence and absence of metabolic activation. Citalopram was not mutagenic in the in vitro mammalian forward gene mutation assay (HPRT) in mouse lymphoma cells or in in vitro/in vivo unscheduled DNA synthesis (UDS) assay in rat liver.

It was not clastogenic in the in vitro chromosomal aberration assay in human lymphocytes or in two in vivo mouse micronucleus assays. Impairment of Fertility Citalopram was administered orally to female and male rats at doses of 32, 48, and 72 mg/kg/day prior to and throughout mating and continuing to gestation. These doses are approximately 8, 12, and 17 times the MRHD of 40 mg based on mg/m 2 body surface area.

Mating and fertility were decreased at doses ≥ 32 mg/kg/day, which is approximately 8 times the MRHD. Gestation duration was increased at 48 mg/kg/day, which is approximately 12 times the MRHD.

13.2Animal Toxicology and/or Pharmacology Retinal Changes in Rats Pathologic changes (degeneration/atrophy) were observed in the retinas of albino rats in the 2-year carcinogenicity study with citalopram. There was an increase in both incidence and severity of retinal pathology in both male and female rats receiving 80 mg/kg/day, which is approximately 19 times the MRHD of 40 mg based on mg/m 2 body surface area. Similar findings were not present in rats treated for two years at the dose of 24 mg/kg/day, in mice treated for 18 months at doses up to 240 mg/kg/day, or in dogs treated for one year at doses up to 20 mg/kg/day, which are approximately 6, 29, and 17 times the MRHD, respectively, based on mg/m 2 body surface area.

Additional studies to investigate the mechanism for this pathology have not been performed, and the potential significance of this effect in humans has not been established.