Venlafaxine Hydrochloride (Page 11 of 15)

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

Tumors were not increased by venlafaxine treatment in mice or rats. Venlafaxine was given by oral gavage to mice for 18 months at doses up to 120 mg/kg per day, which was 1.7 times the maximum recommended human dose on a mg/m 2 basis. Venlafaxine was also given to rats by oral gavage for 24 months at doses up to 120 mg/kg per day. In rats receiving the 120 mg/kg dose, plasma concentrations of venlafaxine at necropsy were 1 times (male rats) and 6 times (female rats) the plasma concentrations of patients receiving the maximum recommended human dose. Plasma levels of the O-desmethyl metabolite (ODV) were lower in rats than in patients receiving the maximum recommended dose. O-desmethylvenlafaxine (ODV), the major human metabolite of venlafaxine, administered by oral gavage to mice and rats for 2 years did not increase the incidence of tumors in either study. Mice received ODV at dosages up to 500/300 mg/kg/day (dosage lowered after 45 weeks of dosing). The exposure at the 300 mg/kg/day dose is 9 times that of a human dose of 225 mg/day. Rats received ODV at dosages up to 300 mg/kg/day (males) or 500 mg/kg/day (females). The exposure at the highest dose is approximately 8 (males) or 11 (females) times that of a human dose of 225 mg/day.

Mutagenesis

Venlafaxine and the major human metabolite, ODV, were not mutagenic in the Ames reverse mutation assay in Salmonella bacteria or the Chinese hamster ovary/HGPRT mammalian cell forward gene mutation assay. Venlafaxine was also not mutagenic or clastogenic in the in vitro BALB/c-3T3 mouse cell transformation assay, the sister chromatid exchange assay in cultured Chinese hamster ovary cells, or in the in vivo chromosomal aberration assay in rat bone marrow. ODV was not clastogenic in the in vitro Chinese hamster ovary cell chromosomal aberration assay or in the in vivo chromosomal aberration assay in rats.

Impairment of Fertility
Reproduction and fertility studies of venlafaxine in rats showed no adverse effects of venlafaxine on male or female fertility at oral doses of up to 2 times the maximum recommended human dose of 225 mg/day on a mg/m 2 basis. However, reduced fertility was observed in a study in which male and female rats were treated with O-desmethylvenlafaxine (ODV), the major human metabolite of venlafaxine, prior to and during mating and gestation. This occurred at an ODV exposure (AUC) approximately 2 to 3 times that associated with a human venlafaxine dose of 225 mg/day.

14 CLINICAL STUDIES

14.1 Major Depressive Disorder

The efficacy of venlafaxine hydrochloride extended-release capsules as a treatment for Major Depressive Disorder (MDD) was established in two placebo-controlled, short-term (8 weeks for study 1; 12 weeks for study 2), flexible-dose studies, with doses starting at 75 mg per day and ranging to 225 mg per day in adult outpatients meeting DSM-III-R or DSM-IV criteria for MDD. In moderately depressed outpatients, the initial dose of venlafaxine was 75 mg per day. In both studies, venlafaxine hydrochloride extended-release capsules demonstrated superiority over placebo on the primary efficacy measure defined as change from baseline in the HAM-D-21 total score to the endpoint visit, venlafaxine hydrochloride extended-release capsules also demonstrated superiority over placebo on the key secondary efficacy endpoint, the Clinical Global Impressions (CGI) Severity of Illness scale. Examination of gender subsets of the population studied did not reveal any differential responsiveness on the basis of gender.

A 4-week study of inpatients meeting DSM-III-R criteria for MDD with melancholia utilizing venlafaxine hydrochloride in a range of 150 to 375 mg per day (divided in a three-times-a-day schedule) demonstrated superiority of venlafaxine hydrochloride over placebo based on the HAM-D-21 total score. The mean dose in completers was 350 mg per day (study 3).

In a longer-term study, adult outpatients with MDD who had responded during an 8-week open-label study on venlafaxine hydrochloride extended-release capsules (75, 150, or 225 mg, once daily every morning) were randomized to continuation of their same venlafaxine hydrochloride extended-release capsules dose or to placebo, for up to 26 weeks of observation for relapse. Response during the open-label phase was defined as a CGI Severity of Illness item score of ≤3 and a HAM-D-21 total score of ≤10 at the day 56 evaluation. Relapse during the double-blind phase was defined as follows: (1) a reappearance of major depressive disorder as defined by DSM-IV criteria and a CGI Severity of Illness item score of ≥4 (moderately ill), (2) 2 consecutive CGI Severity of Illness item scores of ≥4, or (3) a final CGI Severity of Illness item score of ≥4 for any patient who withdrew from the study for any reason.

Patients receiving continued venlafaxine hydrochloride extended-release capsules treatment experienced statistically significantly lower relapse rates over the subsequent 26 weeks compared with those receiving placebo (study 4).

In a second longer term trial, adult outpatients with MDD, recurrent type, who had responded (HAM-D-21 total score ≤ 12 at the day 56 evaluation) and continued to be improved [defined as the following criteria being met for days 56 through 180: (1) no HAM-D-21 total score ≥ 20; (2) no more than 2 HAM-D-21 total scores > 10, and (3) no single CGI Severity of Illness item score ≥ 4 (moderately ill)] during an initial 26 weeks of treatment on venlafaxine hydrochloride [100 to 200 mg per day, on a twice daily schedule] were randomized to continuation of their same venlafaxine hydrochloride dose or to placebo. The follow-up period to observe patients for relapse, defined as a CGI Severity of Illness item score ≥ 4, was for up to 52 weeks. Patients receiving continued venlafaxine hydrochloride treatment experienced statistically significantly lower relapse rates over the subsequent 52 weeks compared with those receiving placebo (study 5).

Table 17: Major Depressive Disorder Studies:
SD: standard deviation; LS Mean: least-squares mean; CI: confidence interval. a Difference (drug minus placebo) in least-squares mean change from baseline * Doses statistically significantly superior to placebo.
Study number Treatment Group Primary Efficacy Measure: HAM-D Score
Mean Baseline Score (SD) LS Mean Change from Baseline Placebo Subtracted Difference a (95%CI)
Study 1 Venlafaxine Hydrochloride Extended-Release Capsules (75 to 225 mg/day)* 24.5 -11.7 -4.45(-6.66, -2.25)
Placebo 23.6 -7.24
Study 2 Venlafaxine Hydrochloride Extended-Release Capsules (75 to 225 mg/day)* 24.5 -15.11 -6.4(-8.45,-4.34)
Placebo 24.9 -8.71
Study 3 Venlafaxine Hydrochloride (immediate release)(150 to 375 mg/day)* 28.2 (0.5) -14.9 -10.2 (-14.4,-6)
Placebo 28.6 (0.6) -4.7

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