Venlafaxine Hydrochloride (Page 9 of 14)
8.5 Geriatric Use
The percentage of patients in clinical studies for venlafaxine hydrochloride extended-release capsules for MDD, GAD, SAD, and PD who were 65 years of age or older are shown in Table 15.
|a In addition, in the premarketing assessment of venlafaxine hydrochloride tablets, 12% (357/2,897) of patients were ≥ 65 years of age.|
Venlafaxine Hydrochloride Extended-Release Capsules
No overall differences in effectiveness or safety were observed between geriatric patients and younger patients, and other reported clinical experience generally has not identified differences in response between the elderly and younger patients. However, greater sensitivity of some older individuals cannot be ruled out. SSRIs and SNRIs, including venlafaxine hydrochloride extended-release capsules, have been associated with cases of clinically significant hyponatremia in elderly patients, who may be at greater risk for this adverse event [see Warnings and Precautions (5.9) ].
The pharmacokinetics of venlafaxine and ODV are not substantially altered in the elderly [see Clinical Pharmacology (12.3)] (see Figure 3). No dose adjustment is recommended for the elderly on the basis of age alone, although other clinical circumstances, some of which may be more common in the elderly, such as renal or hepatic impairment, may warrant a dose reduction [see Dosage and Administration (2.6) ].
8.6 Age and Gender
A population pharmacokinetic analysis of 404 venlafaxine hydrochloride tablets-treated patients from two studies involving both twice daily and three times daily regimens showed that dose-normalized trough plasma levels of either venlafaxine or ODV were unaltered by age or gender differences. Dosage adjustment based on the age or gender of a patient is generally not necessary [see Dosage and Administration (2.6) ] (see Table 15).
8.7 Use in Patient Subgroups
Figure 3: Pharmacokinetics of venlafaxine and its metabolite O-desmethylvenlafaxine (ODV) in special populations.
Abbreviations: ODV, O-desmethylvenlafaxine; AUC, area under the curve; Cmax , peak plasma concentrations;
*Similar effect is expected with strong CYP2D6 inhibitors
9 DRUG ABUSE AND DEPENDENCE
9.1 Controlled Substance
Venlafaxine hydrochloride extended-release capsule is not a controlled substance.
While venlafaxine has not been systematically studied in clinical studies for its potential for abuse, there was no indication of drug-seeking behavior in the clinical studies. However, it is not possible to predict on the basis of premarketing experience the extent to which a CNS-active drug will be misused, diverted, and/or abused once marketed. Consequently, physicians should carefully evaluate patients for history of drug abuse and follow such patients closely, observing them for signs of misuse or abuse of venlafaxine (e.g., development of tolerance, incrementation of dose, drug-seeking behavior).
In vitro studies revealed that venlafaxine has virtually no affinity for opiate, benzodiazepine, phencyclidine (PCP), or N-methyl-D-aspartic acid (NMDA) receptors.
Venlafaxine was not found to have any significant CNS stimulant activity in rodents. In primate drug discrimination studies, venlafaxine showed no significant stimulant or depressant abuse liability. Discontinuation effects have been reported in patients receiving venlafaxine [see Dosage and Administration (2.8) ].
10.1 Human Experience
During the premarketing evaluations of venlafaxine hydrochloride extended-release capsules (for MDD, GAD, SAD, and PD) and venlafaxine hydrochloride tablets (for MDD), there were twenty reports of acute overdosage with venlafaxine hydrochloride (6 and 14 reports in venlafaxine hydrochloride extended-release capsules and venlafaxine hydrochloride tablets patients, respectively), either alone or in combination with other drugs and/or alcohol.
Somnolence was the most commonly reported symptom. Among the other reported symptoms were paresthesia of all four limbs, moderate dizziness, nausea, numb hands and feet, and hot-cold spells 5 days after the overdose. In most cases, no signs or symptoms were associated with overdose. The majority of the reports involved ingestion in which the total dose of venlafaxine taken was estimated to be no more than several-fold higher than the usual therapeutic dose. One patient who ingested 2.75 g of venlafaxine was observed to have two generalized convulsions and a prolongation of QTc to 500 msec, compared with 405 msec at baseline. Mild sinus tachycardia was reported in two of the other patients.
Actions taken to treat the overdose included no treatment, hospitalization and symptomatic treatment, and hospitalization plus treatment with activated charcoal. All patients recovered.
In postmarketing experience, overdose with venlafaxine has occurred predominantly in combination with alcohol and/or other drugs. The most commonly reported events in overdosage include tachycardia, changes in level of consciousness (ranging from somnolence to coma), mydriasis, seizures, and vomiting. Electrocardiogram changes (e.g., prolongation of QT interval, bundle branch block, QRS prolongation), ventricular tachycardia, bradycardia, hypotension, rhabdomyolysis, vertigo, liver necrosis, serotonin syndrome, and death have been reported.
Published retrospective studies report that venlafaxine overdosage may be associated with an increased risk of fatal outcomes compared to that observed with SSRI antidepressant products, but lower than that for tricyclic antidepressants. Epidemiological studies have shown that venlafaxine-treated patients have a higher preexisting burden of suicide risk factors than SSRI-treated patients. The extent to which the finding of an increased risk of fatal outcomes can be attributed to the toxicity of venlafaxine in overdosage, as opposed to some characteristic(s) of venlafaxine-treated patients, is not clear. Prescriptions for venlafaxine hydrochloride extended-release capsules should be written for the smallest quantity of capsules consistent with good patient management, in order to reduce the risk of overdose.
10.2 Management of Overdosage
Consult a Certified Poison Control Center for up-to-date guidance and advice (1-800-222-1222 or www.poison.org). In case of an overdose, provide supportive care, including close medical supervision and monitoring. Treatment should consist of those general measures employed in the management of overdosage with any drug. Consider the possibility of multiple drug overdose. Ensure an adequate airway, oxygenation, and ventilation. Monitor cardiac rhythm and vital signs. Provide supportive and symptomatic measures.
Venlafaxine hydrochloride extended-release capsule, USP is an extended-release capsule for once-a-day oral administration that contains venlafaxine hydrochloride, a serotonin and norepinephrine reuptake inhibitor (SNRI).
Venlafaxine is designated (R/S)-1-[2-(dimethylamino)-1-(4-methoxyphenyl)ethyl] cyclohexanol hydrochloride or (±)-1-[α- [(dimethylamino)methyl]-p-methoxybenzyl] cyclohexanol hydrochloride and has the molecular formula of C17 H27 NO2 HCl. Its molecular weight is 313.86. The structural formula is shown as follows:
Venlafaxine hydrochloride, USP is a white to off-white crystalline powder; soluble in methanol and in water. Its octanol:water (0.2 M sodium chloride) partition coefficient is 0.43.
Drug release is controlled by diffusion through the coating membrane on the spheroids and is not pH-dependent. Venlafaxine hydrochloride extended-release capsules, USP intended for oral administration contains 37.5 mg, 75 mg and 150 mg of venlafaxine. In addition, each capsule contains the following inactive ingredients: colloidal silicon dioxide, cetostearyl alcohol, gelatin, hypromellose, microcrystalline cellulose, polyacrylate dispersion, sodium lauryl sulfate, talc and titanium dioxide. Additionally each 37.5 mg capsule shell contains black iron oxide and each 75 mg and 150 mg capsule shell contains red iron oxide. The capsule is printed with black pharmaceutical ink which contains black iron oxide as coloring agent.
The product complies with USP dissolution test 7.
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