Relative bioavailability of two formulations of venlafaxine extended-release 75-mg capsules in healthy brazilian male volunteers: A single-dose, randomized-sequence, open-label, two-period crossover study in the fasting and fed states

Precision dosing of venlafaxine during pregnancy: a pharmacokinetics modelling approach

OBJECTIVES

Venlafaxine exposure through gestation is affected by the longitudinal changes in maternal physiology. Confounding treatment is also the impact of CYP2D6 polymorphisms affecting plasma concentrations of venlafaxine.

METHODS

A pharmacokinetic modelling approach was employed to assess variations in maternal and foetal cord venlafaxine levels throughout gestation and to identify appropriate doses to maintain venlafaxine levels within the therapeutic range.

KEY FINDINGS

Throughout gestation, there was a significant decrease in simulated venlafaxine trough plasma concentrations in both extensive metaboliser (EM) and ultra-rapid metaboliser (UM) phenotypes. Approximately 70%-87% of EM and UM phenotypes exhibited trough venlafaxine plasma concentrations below the therapeutic level (<25 ng/ml), which increased to 96% at week 30. While for poor metabolizer (PM) phenotypes, the percentage was approximately 4%.

CONCLUSION

The standard daily dose of 75 mg required adjustment for all phenotypes examined during gestation. A daily dose of 37.5-112.5 mg is appropriate for PM throughout pregnancy. For EM, a dose of 225 mg daily in the first trimester, 262.5 mg daily in the second trimester, and 375 mg daily in the third trimester is suggested to be optimal. For UM, a dose of 375 mg daily throughout gestation is suggested to be optimal.

Altered resting-state intra- and inter- network functional connectivity in patients with persistent somatoform pain disorder

Patients with persistent somatoform pain disorder (PSPD) usually experience various functional impairments in pain, emotion, and cognition, which cannot be fully explained by a physiological process or a physical disorder. However, it is still not clear for the mechanism underlying the pathogenesis of PSPD. The present study aimed to explore the intra- and inter-network functional connectivity (FC) differences between PSPD patients and healthy controls (HCs). Functional magnetic resonance imaging (fMRI) was performed in 13 PSPD patients and 23 age- and gender-matched HCs. We used independent component analysis on resting-state fMRI data to calculate intra- and inter-network FCs, and we used the two-sample t-test to detect the FC differences between groups. Spearman correlation analysis was employed to evaluate the correlations between FCs and clinical assessments. As compared to HCs, PSPD patients showed decreased coactivations in the right superior temporal gyrus within the anterior default-mode network and the anterior cingulate cortex within the salience network, and increased coactivations in the bilateral supplementary motor areas within the sensorimotor network and both the left posterior cingulate cortex and the medial prefrontal cortex within the anterior default-mode network. In addition, we found that the PSPD patients showed decreased FNCs between sensorimotor network and audio network as well as visual network, between default-mode network and executive control network as well as audio network and between salience network and executive control network as well as right frontoparietal network, and increased FNCs between sensorimotor network and left frontoparietal network, salience network as well as cerebellum network, which were negatively correlated with the clinical assessments in PSPD patients. Our findings suggest that PSPD patients experience large-scale reorganization at the level of the functional networks, which suggests a possible mechanism underlying the pathogenesis of PSPD.

An Evaluation of Health Service Impacts Consequent to Switching from Brand to Generic Venlafaxine in New Zealand under Conditions of Price Neutrality

OBJECTIVE

To study the health impact on adult New Zealand patients who switch from originator brand to generic venlafaxine.

METHODS

The national pharmacy database was used to select patients using venlafaxine for at least 6 months. Switchers and nonswitchers were identified, and switch behavior was compared for a 12-month follow-up period. Change in health service use following switching was also compared between switchers and nonswitchers including use of the emergency department, hospital, and specialist outpatient services over the same period.

RESULTS

Approximately 12% of all originator brand users switched to generic venlafaxine, at least half of whom continued to use the generic throughout the follow-up period to August 1, 2012. Almost 60% of new users of the generic venlafaxine, however, switched to using the originator brand. Aside from a slight reduction in the use of outpatient services among switchers, there were no significant differences in health services use between switchers and nonswitchers for either existing or new venlafaxine users.

CONCLUSIONS

Although both products remain fully subsidized and available, there is little incentive for prescribers, pharmacists, or patients to switch to the less expensive generic brand. If savings to the national New Zealand budget are to be realized, additional policy measures should be implemented to minimize incentives for multiple and reverse switching, and prescribers, as key opinion leaders, could take the lead in promoting generics to their patients.