Plasma Concentrations Of Active Moiety Research Articles

Therapeutic Drug Monitoring of Venlafaxine and Impact of Age, Gender, BMI, and Diagnosis

AbstractDepression is a common mental disorder affecting more than 264 million people in the world and 5.1% of the Slovak population. Although various antidepressant approaches have been used; still, about 40% of patients do not respond to a first-choice drug administration and one third of patients do not achieve total remission. Therapeutic drug monitoring (TDM) is a method used for quantification and interpreting the drug concentrations in plasma in order to optimize the pharmacotherapy. The aim of this study was to measure the plasma concentrations of venlafaxine, the fourth most prescribed antidepressant in Slovakia, as well as its active metabolite and interpret them with the relevant patients’ characteristics.The study was of retrospective nature and 28 adult patients in total were included. The concentrations of venlafaxine and its active metabolite O-desmethylvenlafaxine (ODV) in plasma were quantified using the validated UHPLC-MS/MS method. The effects of potential influencing factors were evaluated by a multivariate linear regression model.Only 39% of patients reached the venlafaxine active moiety concentrations within the recommended therapeutic range. Plasma concentrations were dependent on age, gender, and duration of the therapy. Venlafaxine metabolism expressed as a metabolite-to-parent concentrations ratio was influenced by a combination of age, gender, and body mass index (BMI). We did not observe any significant difference in plasma concentrations between the patients with a single and recurrent diagnosis of depression. Combining variables made an additive effect on plasma concentrations, for example, active moiety plasma concentrations were higher in older women. In contrast, drug metabolism was higher in older men and men with lower BMI. TDM of venlafaxine is recommended in clinical practice, especially in the elderly when beginning the pharmacotherapy.

Pharmacokinetics of venlafaxine in treatment responders and non-responders: a retrospective analysis of a large naturalistic database.

To assess in a large naturalistic sample, whether clinical response to a treatment with venlafaxine is associated with different patterns of plasma concentrations of active moiety, AM (sum of venlafaxine (VEN) and its active metabolite O-desmethylvenlafaxine (ODVEN)). Applying a regression model, plasma concentrations and plasma concentrations corrected-by-dosage (C/D) for AM were included as independent variable with Clinical Global Impressions-Improvement (CGI-I) scale ratings as dependent variable. Moreover, AM, VEN, and ODVEN were compared between treatment responders and non-responders, defining response as much or very much improved on the CGI-I scale based on the non-parametric Mann-Whitney U (M-W-U) test with a significance level of 0.05. No correlations were found between AM and C/D AM plasma concentrations and CGI-I ratings (regression coefficient 0.0, CI 0.000, 0.001, p = 0.492 for AM and 0.047, CI - 0.065, 0.159, p = 0.408 for C/D AM). Venlafaxine daily dosage did not differ between responders and non-responders (217.7 ± 76.9 vs. 222.0 ± 72.7mg/day, p= 0.45 for M-W-U). Responders displayed lower ODVEN (p = 0.033) and AM (p = 0.031) plasma concentrations than non-responders (p = 0.033 and 0.031, respectively for M-W-U). No other differences were detected. Using a cut-off level of 400ng/mL for AM concentrations, a higher percentage of responders was reported in the group of patients with AM < 400ng/mL (13.04%) compared to patients with AM > 400ng/mL (8%) (p = 0.038). Higher ODVEN and AM concentrations in non-responders than in responders indicate that treatment escalation above upper thresholds of therapeutic reference ranges of venlafaxine is not promising. Hence, the therapeutic reference range for venlafaxine can help in improving outcomes in a measurement-based care model that takes advantage of therapeutic drug monitoring.

Pharmacokinetics and Safety of Risperidone Subcutaneous Implants in Stable Patients With Schizophrenia

A subcutaneous risperidone implant (RI) formulation was developed to improve medication adherence in schizophrenia. Two phase 1 studies were conducted to evaluate the pharmacokinetics of RI in adult patients with schizophrenia. In study 1, all subjects were stable on 4 mg oral risperidone; subsequently, the first subject received 375mg RI for 1 month, and the remaining subjects received 375mg RI for 3 months. In study 2, all subjects were stable on oral risperidone 4mg, 6mg, or 8mg and subsequently received RI 480mg, 720mg, or 960mg, respectively, for 6 months. Blood samples were collected at prespecified time points. Various pharmacokinetic parameters were determined in both studies. In both studies risperidone total active moiety plasma concentrations following RI increased slowly, reached therapeutic levels within approximately 2 days, and remained relatively stable. In study 1, the average concentration for RI was 81.3% of the oral trough concentration and 27.5% of the oral peak concentration. In study 2, the steady-state concentration for RI was comparable to the oral trough concentration of the corresponding dose. Patient disease status remained stable with no major safety issues. RI may represent an alternative formulation for schizophrenia treatment with a lower peak-to-trough plasma drug ratio than oral risperidone.

Effects of the Proton Pump Inhibitors Omeprazole and Pantoprazole on the Cytochrome P450-Mediated Metabolism of Venlafaxine.

A therapeutic drug monitoring database contained plasma concentrations of venlafaxine and its active metabolite O-desmethylvenlafaxine. We considered three groups: a group of patients who received venlafaxine without confounding medications (non-PPI group, n=906); a group of patients who were comedicated with omeprazole (n=40); and a group of patients comedicated with pantoprazole (n=40). Plasma concentrations of venlafaxine, O-desmethylvenlafaxine and active moiety (venlafaxine+O-desmethylvenlafaxine), as well as dose-adjusted plasma concentrations, were compared using non-parametrical tests. Daily doses of venlafaxine did not differ between groups (p=0.949). The Mann-Whitney U test showed significantly higher plasma concentrations of active moiety, as well as venlafaxine and O-desmethylvenlafaxine, in both PPI groups [p=0.023, p=0.011, p=0.026, +29% active moiety, +27% venlafaxine, +36% O-desmethylvenlafaxine (pantoprazole); p=0.003, p=0.039 and p<0.001, +36% active moiety, +27% venlafaxine, +55% O-desmethylvenlafaxine (omeprazole)]. Significantly higher concentration-by-dose (C/D) values for venlafaxine and active moiety were detected in the pantoprazole group (p=0.013, p=0.006, respectively), while in the omeprazole group, C/D ratios for all three parameters-venlafaxine, O-desmethylvenlafaxine and active moiety-were significantly higher (p=0.021, p<0.001 and p<0.001, respectively). Significantly higher plasma concentrations for all parameters (venlafaxine, O-desmethylvenlafaxine, active moiety) suggest clinically relevant inhibitory effects of both PPIs, most likely on the cytochrome P450 (CYP) 2C19-mediated metabolism of venlafaxine. The findings might be the result of different degrees of CYP2C19 involvement, therefore the inhibition of CYP2C19 by both PPIs may lead to an increased metabolism via CYP2D6 to O-desmethylvenlafaxine.

Clinical response in a risperidone-medicated naturalistic sample: patients' characteristics and dose-dependent pharmacokinetic patterns.

The purpose of this study was to disentangle an association between plasma concentrations of risperidone (RIS), its active metabolite 9-hydroxyrisperidone (9-OH-RIS) and the active moiety, AM (RIS+9-OH-RIS), and clinical response in a naturalistic sample. Plasma concentrations of RIS, 9-OH-RIS and AM in patients out of a therapeutic drug monitoring (TDM) database were compared between responders (n=64) and non-responders (n=526) using the Clinical Global Impressions (CGI) Scale. Daily dosage of risperidone did not differ between responders and non-responders. Differences for active moiety plasma levels between the two groups did not reach statistical significance. However, responders showed lower plasma concentrations of the parent compound RIS as well as lower metabolic ratios RIS/9-OH-RIS than non-responders (p=0.017 and p=0.034). These differences did not remain after controlling for age and baseline symptoms. Furthermore, the cohort was split into two subgroups based on the daily dosage: patients under high (≥6mg/day) (R H, n=187) and patients under lower dosages (<6mg) (R L, n=403) of risperidone. Differences between responders and non-responders after controlling for demographic and clinical characteristics remained only for plasma concentrations of active moiety in the lower-dose medicated groups; non-responders showed higher active moiety plasma concentrations than responders. Understanding the mechanisms involved and factors associated with the clinical response in patients medicated with antipsychotics is of great interest. Our data imply that clinical response to an antipsychotic treatment cannot be attributed to a single pharmacokinetic pattern. It seems to be rather a complex patchwork of influencing factors such as demographic and clinical characteristics as well as the metabolizer status as surrogate of CYP activity. It seems that the ratio between RIS and 9-OH-RIS may play a crucial role in mediating the clinical effect.

Risperidone-induced extrapyramidal side effects: is the need for anticholinergics the consequence of high plasma concentrations?

Antipsychotic drugs can induce various undesirable adverse motor reactions, such as extrapyramidal side effects (EPS). A widely accepted pharmacodynamic mechanism underlying EPS includes an increase in striatal D2-receptor occupancy. However, less is known about the pharmacokinetic background of EPS. The aim of this study was to analyze in-vivo possible pharmacokinetic patterns underlying biperiden-treated EPS in risperidone (RIS)-medicated patients. A large therapeutic drug monitoring database containing plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone (9-OH-RIS) of 2293 adult inpatients and outpatients was analyzed. Two groups were compared: a group receiving RIS (n=772) and a group comedicated with biperiden (n=68). Plasma concentrations, dose-adjusted plasma concentrations (C/D) of RIS, 9-OH-RIS, and active moiety (AM) (RIS+9-OH-RIS) as well as ratios of concentrations for metabolite to parent drug (9-OH-RIS/RIS) were computed. We compared the plasma concentrations of the different compounds between the two groups considering the prescription of biperiden as an indirect report of EPS. The daily dosage of RIS did not differ between groups. No differences were detected in case of plasma concentrations and C/D of RIS and active metabolite between the groups. However, plasma concentrations of the AM were significantly higher in the comedicated group (P=0.032) and showed a trend in terms of the active metabolite 9-OH-RIS (P=0.053). Data indicate enhanced AM plasma concentrations of RIS in patients comedicated with biperiden as an EPS treatment. This might underscore an association between higher plasma concentrations of the AM and treatment-requiring EPS.

Pharmacokinetic patterns of risperidone-associated adverse drug reactions.

The aim of the study was to investigate a correlation between plasma concentrations of risperidone (RIS), its active metabolite 9-hydroxyrisperidone (9-OH-RIS) and the active moiety (AM) (RIS + 9-OH-RIS), and adverse drug reactions (ADRs) in a naturalistic sample. Plasma concentrations of RIS, 9-OH-RIS, and AM in patients out of a therapeutic drug monitoring (TDM) database complaining ADRs were categorized according to the Udvalg for Kliniske Undersogelser side effect rating scales (UKU) (n=97) and compared to patients without ADRs (n=398). Patients in the ADR group received a significantly lower daily dosage of risperidone (trimmed mean 3.64mg/day) than patients without ADRs (4.40mg/day). No differences were found for active moiety plasma concentrations between the groups (p=0.454). Differences were detected only in the case of dose-adjusted plasma concentration values (concentration-by-dose, C/D) for 9-OH-RIS, being higher in patients reporting ADRs (4.78ng/mL/mg) than in patients without ADRs (4.3ng/mL/mg) (p=0.037 for Mann-Whitney U test). Note that differences for non-adjusted 9-OH-RIS plasma levels between groups failed to reach significance (p=0.697). Our findings are consistent with previous data supporting a prominent role of 9-hydroxyrisperidone, but not of risperidone with regard to ADRs. When studying the various subgroups of reported ADRs separately, the size of these subsamples offers some plausible limitations by reducing the power of the analysis.

Management of antipsychotic treatment discontinuation and interruptions using model-based simulations.

BackgroundMedication nonadherence is a well described and prevalent clinical occurrence in schizophrenia. These pharmacokinetic model-based simulations analyze predicted antipsychotic plasma concentrations in nonadherence and treatment interruption scenarios and with treatment reinitiation.MethodsStarting from steady state, pharmacokinetic model-based simulations of active moiety plasma concentrations of oral, immediate-release risperidone 3 mg/day, risperidone long-acting injection 37.5 mg/14 days, oral paliperidone extended-release 6 mg/day, and paliperidone palmitate 117 mg (75 mg equivalents)/28 days were assessed under three treatment discontinuation/interruption scenarios, ie, complete discontinuation, one week of interruption, and four weeks of interruption. In the treatment interruption scenarios, pharmacokinetic simulations were performed using medication-specific reinitiation strategies.ResultsFollowing complete treatment discontinuation, plasma concentrations persisted longest with paliperidone palmitate, followed by risperidone long-acting injection, while oral formulations exhibited the most rapid decrease. One week of oral paliperidone or risperidone interruption resulted in near complete elimination from the systemic circulation within that timeframe, reflecting the rapid elimination rate of the active moiety. After 1 and 4 weeks of interruption, minimum plasma concentrations were higher with paliperidone palmitate than risperidone long-acting injection over the simulated period. Four weeks of treatment interruption followed by reinitiation resulted in plasma levels returning to predicted therapeutic levels within 1 week.ConclusionDue to the long half-life of paliperidone palmitate (25–49 days), putative therapeutic plasma concentrations persisted longest in simulated cases of complete discontinuation or treatment interruption. These simulations may help clinicians better conceptualize the impact of antipsychotic nonadherence on plasma concentrations, and the impact of medication-specific reinitiation strategies after intermittent nonadherence.

Clinical response to risperidone in relation to plasma drug concentrations in acutely exacerbated schizophrenic patients

There are no data indicating a clear relationship between the clinical effect of risperidone and plasma drug concentration. In this study, 51 patients with acutely exacerbated schizophrenia received 6 mg risperidone/day for 4 weeks. A clinical evaluation using the Brief Psychiatric Rating Scale (BPRS) and Udvalg for Klinicke Undersøgelser (UKU) side effect rating scale were performed at baseline and each week. Significant (P < 0.05) correlations were found between plasma concentrations of risperidone and improved total BPRS scores, positive and cognitive symptoms. Plasma concentrations of the active moiety were significantly (P < 0.05) correlated with improved total BPRS scores. Improved score and percent improvement in anxiety-depression subscale were significantly (P < 0.01) correlated with plasma concentrations of the active moiety. The sum of total UKU side effect scores from 1 to 4 weeks was significantly correlated with plasma concentration of both risperidone (rs = 0.319, P < 0.05) and active moiety (rs = 0.373, P < 0.01). The sum of the psychic subgroup scores was significantly correlated with plasma concentrations of active moiety (rs = 0.318, P < 0.05). Results suggest that plasma drug concentrations are, to some extent, associated with improved scores in some psychopathological schizophrenic symptoms and sedative side effects. These findings should be replicated with a larger patient sample.

Serum prolactin levels, plasma risperidone levels, polymorphism of cytochrome P450 2D6 and clinical response in patients with schizophrenia

The object of this study is to assess 1) the relationship between plasma antipsychotic drug concentration, serum prolactin levels and the clinical efficacy of risperidone, 2) the relationship between the CYP2D6 polymorphisms and metabolizing of risperidone and 3) the role of 9-hydroxyrisperidone in elevating prolactin levels. One-hundred and eighteen Chinese schizophrenia patients (40 males, 78 females, age 15-60 years) were given risperidone at dosages ranging from 2-8 mg/day for 8 weeks. Clinical efficacy was determined using the Brief Psychiatric Rating Scores (BPRS). Serum prolactin levels were assayed before and after the 8 week treatment and plasma risperidone and 9-hydroxyrisperidone levels were also measured at the end of the 8-week treatment. The results showed there was no significant correlation between the concentration of active moiety and clinical response. Risperidone treatment significantly increased serum prolactin levels. Furthermore, changes of prolactin levels were not correlated with the clinical response. For the risperidone/ 9-hydroxyrisperidone ratio, there was a statistically significant difference among the CYP2D6*1/*1, *1/*10, *10/*10 genotypes (Kruskal-Wallis test, p = 0.012). No significant differences were found in the concentration of 9-hydroxyrisperidone and active moiety among the genotypes. In addition, the concentration of 9-hydroxyrisperidone was not significantly correlated with the increase of serum prolactin. In conclusion, our study has, for the first time, produced evidence that in Chinese schizophrenic patients, the metabolism of risperidone is dependent on CYP2D6. Neither changes in serum prolactin levels nor plasma concentration of active moiety were significantly correlated with clinical efficacy of risperidone. 9-hydroxyrisperidone may not play a predominant role in elevating serum prolactin level.

Prediction of response to risperidone treatment with respect to plasma concencentrations of risperidone, catecholamine metabolites, and polymorphism of cytochrome P450 2D6

In the present study, we examined the relationships between plasma concentrations of risperidone and clinical responses, extrapyramidal symptoms, plasma levels of cotinine and caffeine, or cytochrome (cyp)2D6 genotypes. In addition, we also investigated the relationships between plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) or homovanillic (HVA) acid and clinical responses to risperidone. One hundred and 36 patients (male/female: 58/78, age 37+/-13 years) who met DSM-IV criteria for schizophrenia, schizoaffective disorder, delusional disorder and brief psychotic disorder, and who were being treated with risperidone alone, were evaluated regarding their clinical improvement and extrapyramidal symptoms using the Positive and Negative Syndrome Scale (PANSS) and Simpson and Angus (SAS), respectively, and plasma levels of cotinine, caffeine, MHPG and HVA were analysed by high-performance liquid chromatography. The cyp2D6*5 and *10 alleles were identified using the polymerase chain reaction. There was a positive correlation between plasma levels of risperidone plus 9-hydroxyrisperidone (active moiety) and SAS scores, but not the PANSS. Pretreatment HVA levels in responders were higher than those in nonresponders. In addition, there was a negative correlation between changes in HVA levels and improvement in PANSS scores. There was no association between plasma levels of risperidone and plasma levels of cotinine or caffeine. Furthermore, there were no differences in the risperidone/9-hydroxyrisperidone ratio, clinical improvements and extrapyramidal symptoms among cyp2D6 genotypes. These results indicate that pretreatment HVA levels and plasma concentrations of active moiety might play a part in predicting the clinical response and occurrence of extrapyramidal symptoms, respectively, when treating patients with risperidone.

Extended inhibition of platelet aggregation with the orally active platelet inhibitor SC-54684A.

Platelet aggregation is important in thrombotic events, and platelets play a major role in the etiology of several cardiovascular diseases. Platelet aggregation requires the binding of fibrinogen (fgn) to activated platelets. Synthetic peptides modeled after the RGD binding sequence on the fgn alpha-chain block the platelet glycoprotein (GP) IIb/IIIa receptor for fgn and effectively inhibit aggregation. SC-54684A (SCp, orally active prodrug of the active moiety SC-54701, SCa) is a mimetic of the RGD-containing peptide sequence that is recognized by the platelet GPIIb/IIIa receptor. SCa blocks the binding of fgn to the platelet and therefore prevents platelet aggregation in response to all agonists. SCp was administered orally at 1.25, 2.5, 5.0, and 7.5 mg/kg in a single-dose, dose-ranging study. Blood samples were taken periodically for 24 hours, and platelet-rich plasma was prepared and tested for inhibition of ex vivo collagen-induced platelet aggregation. The plasma concentration of active moiety was determined by bioassay. The time, inhibition, and concentration data were used to predict two doses that would result in minimum daily inhibition levels of 30% and 70% when administered twice daily (0.6 and 2.4 mg/kg, respectively). SCp was administered orally to conscious dogs twice daily for 14 days (after dose adjustment). Blood samples were obtained at daily peak and trough plasma levels (predicted from dose-ranging study). Inhibition of ex vivo collagen-induced platelet aggregation and concentration of active moiety in the plasma were determined. Average inhibition of platelet aggregation and plasma concentration of active moiety amounted to approximately 21% and 14 ng/mL at 1.5 mg/kg BID and 75% and 24 ng/mL at 2.4 ng/kg BID at daily minimum plasma levels (trough) in steady state. Platelet counts in the 2.4-mg/kg group declined from 3.2 x 10(5)/microL to 2.5 x 10(5)/microL in the first 9 days of dosing, with no further decline despite continued administration of compound. No changes were observed in the animals receiving 1.5 mg/kg. The results of the dose-ranging study show that oral administration of SCp results in dose-dependent inhibition of platelet aggregation. As shown in the 14-day administration, this dose-dependent inhibition can be maintained for an extended period while exhibiting no adverse effects. SCp is a leading candidate for development and is currently in clinical trials.

A new method for measurement of plasma concentration of orally active glycoprotein IIb/IIIa antagonists

A bioassay for determining concentrations of antiplatelet compounds in plasma or aqueous solution has been developed. The method uses an aliquot of plasma from treated animals to inhibit collagen-induced platelet aggregation in pooled platelet-rich plasma (PRP) obtained from donor dogs. The concentration in plasma from treated animals was estimated using a standard curve of inhibition established using plasma from untreated animals which had been spiked with known amounts of compound. For independent validation, plasma concentrations of certain compounds were determined in identical dog plasma samples by both bioassay and HPLC. Results from the two methods were concordant. The bioassay provides an accurate and sensitive method for measuring antiplatelet activity without the need for extraction of plasma samples and may be used to measure activity in any solution which is compatible with PRP. This assay is routinely used to provide an estimate of absorption of prodrugs and systemic conversion to active compound after oral dosing. Some of the compounds of interest are ester-acid pairs with the inactive ester prodrug being cleaved to the active acid following administration. Compounds were administered orally (ester) or IV (acid) and blood samples were taken periodically for 24 hours. Plasma concentration of active moiety was determined for each time point and the area under the curve (AUC) of concentration vs. time was calculated. Comparing the AUCs for oral and IV routes of administration yielded the Oral Systemic Activity (OSA), a measure of active compound available after oral dosing.