Safety, tolerability, and pharmacokinetics of once-daily trazodone extended-release caplets in healthy subjects.

OBJECTIVE: To characterize the pharmacokinetics, safety, and tolerability of an extended-release formulation of trazodone hydrochloride (HCl), Trazodone Contramid® Once-a-Day (TzCOAD) developed as scored 150-mg and 300-mg caplets for oncedaily administration. METHODS: Relative bioavailability studies compared the pharmacokinetics of TzCOAD and trazodone immediate-release (TzIR) tablets following single- and multiple-dose administration. In addition, the effect of food on the pharmacokinetics of TzCOAD was assessed. RESULTS: After single-dose administration of 300 mg TzCOAD, trazodone AUC and C(max) were approximately 20% and 60% lower, respectively, than for TzIR 100-mg tablets administered as 3 doses, 8 h apart. After multipledose administration of 300 mg daily for 7 days, TzCOAD given once daily and TzIR given 3 times a day were equivalent with respect to AUC, while C(max) was 43% lower for TzCOAD. Trazodone AUC following single-dose administration of TzCOAD was similar to AUC at steady state, suggesting that steady-state exposure can be predicted from single-dose data. When TzCOAD was taken shortly after ingestion of a high-fat meal, C(max) increased 86% compared with fasting conditions. However, AUC and t(max) were not affected by food. CONCLUSION: Administration of TzCOAD 300 mg once daily provides equivalent steady-state exposure to, with a lower C(max) than, TzIR 100 mg given 3 times a day. A high-fat meal results in an increase in C(max), but there is no substantial effect on AUC.

Effect of hypoxia on cytochrome P450 activity and expression.

In the last three decades, numerous reports have shown that patients with chronic pulmonary disease and with heart failure with hypoxemia cleared drugs at a lower rate than healthy volunteers. As a consequence decreased clearance, drug toxicity is frequent in these patients. The reduction in drug clearance is due to a decrease in activity of cytochrome P450 isoforms, partly associated to the hypoxemia. With in vivo animal models, acute moderate hypoxia (PaO2 of around 35-50 mm Hg) reduces the clearance of drugs biotransformed by CYP1A1, CYP1A2, CYP2B6, CYP2C9, CYP2C19 and CYP2E1, although hypoxia does not affect the clearance of drugs biotransformed by CYP3A6. Ex vivo and in vitro experiments demonstrate that hypoxia down-regulates CYP1A1, CYP1A2, CYP2B6, CYP2C9 and CYP2C19, decrease preceded by a reduction in activity. On the other hand, acute moderate hypoxia up-regulates CYP3A6. The changes in protein expression are preceded by modifications in the mRNA coding for the proteins. The effect of hypoxia on hepatic cytochrome P450 is carried out by serum mediators, e.g. interferon-gamma, interleukin-1beta, and interleukin-2 are responsible for the decrease in activity and in expression of cytochrome P450 isoforms, and erythropoietin accounts for the increase in CYP3A6. Probably several mechanisms underlie and contribute to the decrease in activity and down-regulation of cytochrome P450 isoforms by hypoxia, e.g. reducing potentiation factors, inducing repressor elements and activating negative regulatory elements. The up-regulation of CYP3A6 implies a PTK- and p42/44MAPK-dependent stabilization/activation, nuclear translocation of HIF-1 and AP-1, binding to CYP3A6 promoter, and transactivation of the gene to induce CYP3A6 expression.

Effects of labor on placental expression of superoxide dismutases in preeclampsia.

A decreased antioxidant activity for superoxide dismutases (SODs) in the placenta was reported in preeclampsia (PE). However, it is unclear if this reduced enzymatic activity can be attributed to a specific SOD isoform. Moreover, the specific spatial SOD expression in the placenta and the impact of the mode of delivery on the latter are still lacking. There are three known SOD isoforms: SOD1 (cytosolic), SOD2 (mitochondrial) and SOD3 (extracellular). Our main objective was to characterize by RT-PCR, western blot and immunolocalization, the expression of SOD1, SOD2, and SOD3 in placentas of normotensive (n = 23) and PE pregnancies (n = 25) according to the presence or absence of labor, the sampling site (peri-insertion, mid-disc and periphery) and the placental layer: amnion-chorion, villi, and maternal side layer (MS). In absence of labor (cesarean), SOD1 expression in the placental villi and MS was lower in PE than in controls (p < 0.049). In presence of labor (vaginal deliveries), SOD1 expression in the amnion-chorion only was higher in PE than controls (p = 0.014). Additionally, SOD2 and SOD3 expression in presence of labor were higher in all three layers in PE than controls, with a strong positive correlation between these two SODs (mRNA; r > 0.65, p < 0.008). The sampling site and gestational age had no effect on SOD expression within the placenta. In this study, we showed that the reported decrease for SOD activity in PE may be attributed to SOD1 in absence of labor. Also, this is the first study characterizing specific SOD isoforms according to the mode of delivery. We demonstrated in PE that labor upregulates SOD1 in fetal membranes as well as SOD2 and SOD3 in the whole placenta.

Cytochrome P450 down-regulation by serum from humans with a viral infection and from rabbits with an inflammatory reaction.

Serum from humans with an upper respiratory viral infection (HS(URVI)) and from rabbits with a turpentine-induced acute inflammatory reaction (RS(TIAR)) reduces the activity of hepatic cytochrome P450 (P450) following 4 h of incubation. The aim of the present study was to assess the effect of HS(URVI) and RS(TIAR) on P450 activity and expression following 24 h of incubation with hepatocytes from control (H(CONT)) and rabbits with a TIAR (H(INFLA)). RS(TIAR) incubated with H(CONT) for 24 h reduced P450 content and activity, and CYP3A6 by 45%, without changing CYP1A1 and 1A2; when incubated with H(INFLA), RS(TIAR) decreased P450 content and activity without affecting CYP1A1 or 1A2. HS(URVI) incubated for 4 h with H(CONT) decreased P450 activity without affecting the amounts of CYP1A1, 1A2, or 3A6, although when incubated for 24 h, P450 activity and CYP3A6 amount decreased. HS(URVI) incubated with H(INFLA) for 4 h reduced P450 content and activity, and incubated for 24 h reduced activity, P450 content, and amount of CYP1A1 and 1A2 proteins. The present study demonstrates that 1) the effect of RS(TIAR) and HS(URVI) depends upon the susceptibility of the hepatocyte, i.e., H(CONT) or primed H(INFLA); 2) P450 down-regulation is preceded by a decrease in P450 activity; 3) the nature of the inflammatory reaction determines the repercussions on P450 activity and expression; and 4) CYP3A6 is more vulnerable than CYP1A1 and 1A2 to the down-regulation provoked by an inflammatory challenge.