Successful Prediction of Human Steady-State Unbound Brain-to-Plasma Concentration Ratio of P-gp Substrates Using the Proteomics-Informed Relative Expression Factor Approach

In order to optimize central nervous system (CNS) drug development, accurate prediction of the drug's human steady-state unbound brain interstitial fluid-to-plasma concentration ratio (K_p,uu,brain ) is critical, especially for drugs that are effluxed by the multiple drug resistance transporters (e.g., P-glycoprotein, P-gp). Due to lack of good in vitro human blood-brain barrier models, we and others have advocated the use of a proteomics-informed relative expressive factor (REF) approach to predict K_p,uu,brain . Therefore, we tested the success of this approach in humans, with a focus on P-gp substrates, using brain positron emission tomography imaging data for verification. To do so, the efflux ratio (ER) of verapamil, N-desmethyl loperamide, and metoclopramide was determined in human P-gp-transfected MDCKII cells using the Transwell assay. Then, using the ER estimate, K_p,uu,brain of the drug was predicted using REF (ER approach). Alternatively, in vitro passive and P-gp-mediated intrinsic clearances (CLs) of these drugs, estimated using a five-compartmental model, were extrapolated to in vivo using REF (active CL) and brain microvascular endothelial cells protein content (passive CL). The ER approach successfully predicted K_p,uu,brain of all three drugs within twofold of observed data and within 95% confidence interval of the observed data for verapamil and N-desmethyl loperamide. Using the in vitro-to-in vivo extrapolated clearance approach, K_p,uu,brain was reasonably well predicted but not the brain unbound interstitial fluid drug concentration-time profile. Therefore, we propose that the ER approach be used to predict K_p,uu,brain of CNS candidate drugs to enhance their success in development.

Validation and application of high performance liquid chromatographic method for the estimation of metoclopramide hydrochloride in plasma

The objective of this study was validation of a reverse phase HPLC method for the estimation of metoclopramide HCl in plasma already validated for determination of metoclopramide HCl in tablets dosage form. A reverse chromatographic method was used for estimation of metoclopramide HCl with the mobile phase of acetonitrile, 20mM potassium dihydrogen phosphate buffer solution (pH 3.0 adjusted with orthophosphoric acid) in the ratio of 40: 60. The column used was Waters C18 3.9×300mm µBondapak (RP). The flow rate of the mobile phase was 2ml/ minute. The detector was set at the wavelength of 275nm. This method validated in plasma and was found to be linear, with correlation coefficient (R²), value of 0.9988, in the range of 48 ng/ml-0.25ng/ml. The method modified was accurate, precise, sensitive and showed good stability results. The % RSD of the retention time and peak area of metoclopramide HCl was 0.19% and 1.44% respectively. All the parameters such as specificity, linearity, range, accuracy, precision, system suitability, solution stability, detection and quantification limits were evaluated to validate this method and were found within the acceptance limits. The method can be effectively used for estimation of metoclopramide HCl in plasma.

Second derivative synchronous fluorescence spectroscopy for the simultaneous determination of metoclopramide and pyridoxine in syrup and human plasma

A rapid, simple, and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous determination of metoclopramide (MT) and pyridoxine (PY) in a binary mixture. The method is based on measurement of the native fluorescence of these drugs at delta lambda = 80 nm in methanol. The different experimental parameters affecting the native fluorescence of the drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the ranges of 0.02-0.4 and 0.1-2 microg/mL for MT and PY, respectively. The limits of detection were 0.003 and 0.007 microg/mL and the limits of quantification were 0.008 and 0.02 microg/mL for MT and PY, respectively. The proposed method was successfully applied to the determination of MT and PY in synthetic mixtures and in commercial syrup. The results were in good agreement with those obtained with a reported method. The high sensitivity attained by the proposed method allowed the determination of MT in spiked and real human plasma samples. The mean percent recoveries of MT from spiked and real human plasma (n = 3) were 93.72 +/- 3.15 and 89.72 +/- 2.19 respectively.

Metoclopramide modifies oral cephalexin pharmacokinetics in dogs

The purpose of this study was to investigate whether previous administration of metoclopramide affects cephalexin pharmacokinetics after its oral administration in dogs as well as whether these changes impair its predicted clinical efficacy. Six healthy beagle dogs were included in this study. Oral 25 mg/kg cephalexin monohydrate and intravenous 0.5 mg/kg metoclopramide HCl single doses were administered. Each dog received cephalexin or cephalexin following metoclopramide, with a 2-week washout period. Plasma concentrations of cephalexin were determined by microbiological assay. Cephalexin peak plasma concentration and area under the curve from 0 to infinity significantly increased from 18.77+/-2.8 microg/mL and 82.65+/-10.4 microg.h/mL to 21.88+/-0.8 microg/mL and 113.10+/-20.9 microg.h/mL, respectively, after pretreatment with metoclopramide. No differences between treatments were found for other pharmacokinetic parameters. Pharmacokinetic/pharmacodynamic indices calculated for highly susceptible staphylococci were similar for both experiences. Metoclopramide pretreatment may have increased cephalexin absorption by affecting its delivery to the intestine, and/or enhancing intestinal transporter PEPT1 function. Neither difference in the efficacy of cephalexin nor an increase in toxicity is expected as a result of this modification. Consequently, no dose adjustment is required in cephalexin-treated patients pretreated with metoclopramide.

Rapid-onset intranasal delivery of metoclopramide hydrochloride Part II: Safety of various absorption enhancers and pharmacokinetic evaluation

In the present study, several nasal absorption enhancers, used in metoclopramide hydrochloride (MCP HCl) nasal solutions, have been screened for their possible damaging effect in the in vitro human erythrocytes lysis experiment. Moreover, the in vivo leaching of biological markers from the rat nasal epithelium was used as a quantitative assessment for possible nasal mucosal irritation whereby the extent of release of total protein and lactate dehydrogenase (LDH) in the nasal lavage fluid was determined. Results showed that insignificant hemolysis from normal saline (P<0.05) occurred with the enhancer protamine sulphate while poly-l-arginine and sodium cholate demonstrated very low (<15%) hemolysis and caused insignificant protein and LDH release from the rat nasal mucosa. Conversely, sodium deoxycholate and chitosan polymers (either of low or high molecular weight) showed high (>60%) hemolysis in vitro and the release of the biological markers in vivo was significantly higher (P<0.05) than the control solution (no enhancer). A significant correlation (P<0.05) existed between the enhancement effect of MCP HCl nasal absorption and the amounts of protein (r=0.85) and LDH (r=0.88). Furthermore, the pharmacokinetics of MCP HCl was determined after intravenous (IV), per-oral and intranasal administration of 10mg drug dose in rabbits. The application of a nasal spray (NS) solution containing 0.5% sodium cholate resulted in a significant improvement (P<0.05) in both the rate and extent of absorption of MCP HCl where the T(max) achieved was 23.3min as compared to 50min in case of the oral solution while the area under the serum concentration-time curve (AUC(0-infinity)) were 506.1, 434.9 and 278.7microg/mlmin for IV, NS and oral solutions, respectively. These values corresponded to absolute bioavailabilities of 87.21 and 55.61% for the NS and oral solutions, respectively. It could thus be concluded that NS of MCP HCl represents a viable approach to achieving rapid and high systemic drug absorption during the emergency treatment of severe emesis.

Nasal absorption of metoclopramide from different Carbopol 981 based formulations: In vitro, ex vivo and in vivo evaluation

There is a need for nasal drug delivery of metoclopramide HCI (MTC) in specific patient populations where the use of commercially available intravenous and oral dosage forms may be inconvenient and/or unfeasible. In this perspective, nasal dosage forms (solution, gel and lyophilized powder) of MTC were prepared by using a mucoadhesive polymer Carbopol 981 (CRB 981). The drug release studies of formulations were performed by using a modified horizontal diffusion chamber with cellulose membrane and excised cattle nasal mucosa as diffusion barriers. After the ex vivo experiments, the morphological appearances of the nasal mucosa were analyzed with the light microscopic studies. In vivo experiments were carried on sheep model. The release of MTC from solution and powder formulations was found higher than gel formulation (p < 0.05) and no severe damage was found on the integrity of nasal mucosa after ex vivo experiments. The penetration enhancing effect of dimethyl-beta-cyclodextrin (DM-beta-CD) used in powder formulations was observed in ex vivo and in vivo experiments. In contrast to in vitro and ex vivo experiments the nasal bioavailability of gel formulation was found higher than those of the solution and powder (p < 0.05) and might represent a promising novel tool for the systemic delivery of MTC.

Clinical application of an enzyme immunoassay for cholecystokinin-like immunoreactive substance for determination of the human plasma levels: the effect of metoclopramide on gastrointestinal peptides and stress-related hormones

Metoclopramide, a prokinetic drug, is widely used to treat vomiting and nausea. Delayed gastric emptying and continual stress are considered important factors, among others, that induce nausea and vomiting. One gastrointestinal motility regulatory factor has been assumed to be the induction of changes in the levels of peptides such as gastrin, somatostatin, motilin, and cholecystokinin (CCK) in plasma. In contrast, adrenocorticotropic hormone (ACTH) and cortisol are used as indicators of stress. Here, we studied the effects of metoclopramide on human plasma gastrin-, somatostatin-, motilin-, and CCK-like immunoreactive substances (ISs) and ACTH-IS and cortisol under stress conditions using repetitive blood sampling in healthy subjects. Metoclopramide hydrochloride at a dose of 30 mg or placebo was orally administered to five healthy male volunteers. Blood samples were taken before and 20, 40, 60, 90, 120, 180, and 240 min after administration, subject to extracting procedures, and submitted to a highly sensitive enzyme immunoassay system. A single administration of metoclopramide caused significant increases in plasma somatostatin-IS levels compared with the placebo. Metoclopramide significantly decreased plasma gastrin- and suppressed ACTH-IS and cortisol levels compared with the placebo. We hypothesize that metoclopramide might have an accelerating gastric-emptying effect and a modulatory effect on the hypothalamo-pituitary-adrenal (HPA) axis and the autonomic nervous function. These effects might be beneficial in stress-related diseases, which suggest that this medicine has clinicopharmacological activities.

Validated method for determination of bromopride in human plasma by liquid chromatography--electrospray tandem mass spectrometry: application to the bioequivalence study

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry method for the quantification of bromopride I in human plasma is presented. Sample preparation consisted of the addition of procainamide II as the internal standard, liquid-liquid extraction in alkaline conditions using hexane-ethyl acetate (1 : 1, v/v) as the extracting solvent, followed by centrifugation, evaporation of the solvent and sample reconstitution in acetonitrile. Both I and II (internal standard, IS) were analyzed using a C18 column and the mobile-phase acetonitrile-water (formic acid 0.1%). The eluted compounds were monitored using electrospray tandem mass spectrometry. The analyses were carried out by multiple reaction monitoring (MRM) using the parent-to-daughter combinations of m/z 344.20 > 271.00 and m/z 236.30 > 163.10. The areas of peaks from analyte and IS were used for quantification of I. The achieved limit of quantification was 1.0 ng/ml and the assay exhibited a linear dynamic range of 1-100.0 ng/ml and gave a correlation coefficient (r) of 0.995 or better. Validation results on linearity, specificity, accuracy, precision and stability, as well as application to the analysis of samples taken up to 24 h after oral administration of 10 mg of I in healthy volunteers demonstrated the applicability to bioequivalence studies.

In vitro effects of cisapride, metoclopramide and bethanechol on smooth muscle preparations from abomasal antrum and duodenum of dairy cows

The objective of this study was to investigate the effects of cisapride (CIS), metoclopramide (MET) and bethanechol (BET) on contractility parameters from smooth muscle preparations of the abomasal antrum and proximal duodenum of cows. Smooth muscle preparations were harvested shortly post-mortem from 42 healthy dairy cows, and concentration-response curves were performed by cumulative application of the drugs. Cisapride and MET did not have any significant effect on the contractility parameters studied, while BET induced a significant, concentration-dependent increase in basal tone (BT), mean amplitude (Amean), and area under the curve (AUC) in smooth muscle preparations from the abomasal antrum, but not from the duodenum. The effect of BET on BT was more pronounced in specimens with longitudinal orientation while the maximal obtainable effect (Vm) in Amean was more pronounced in circular-oriented preparations. Atropine (1 x 10-5 m) significantly inhibited the effect of BET, whereas pre-incubation with hexamethonium or tetrodotoxin (TTX) had no effect, suggesting that the effect was mediated by cholinergic receptors on the smooth muscle. The results may be relevant to diseases or disorders associated with gastric emptying and gastric hypomotility. Further investigations are warranted to investigate the potential ability of BET to enhance abomasal emptying of adult dairy cows.

Assessment of a controlled release hydrophilic matrix formulation for metoclopramide HCl

Metoclopramide HCl showed controlled release behavior when embedded in a hydrophilic matrix of chitosan and sodium alginate. The in vitro release data was found to be first order according to the Higuchi mechanism. An in vivo evaluation of the metoclopramide controlled release matrix on six male volunteers was carried out. The plasma samples were analyzed using a high-performance liquid chromatography (HPLC) method using a mobile phase of acetonitrile:acetic acid (30:70), with the pH adjusted to 4.7, a reverse phase Hypersil BDS Phenyl column (4 microm, 250 x 4 mm) and the detection was performed at 305 nm. The controlled release formula was found to be effective in delaying absorption (t(max) 4.5h as compared to 1.2h), reducing the peak plasma concentrations (C(max) 63.4 ng/ml as compared to 95.9 ng/ml) and maintaining higher concentrations during the elimination phase when compared to the immediate release formula. This proves the suitability of the suggested system for further studies.

RP-HPLC method with electrochemical detection for the determination of metoclopramide in serum and its use in pharmacokinetic studies

A rapid and sensitive reversed-phase high performance liquid chromatographic method has been developed for the determination of metoclopramide in serum. The assay was performed after single extraction with ethyl ether using methyl parahydroxybenzoate as internal standard. Chromatographic separations were performed on C(18) stationary phase with a mobile phase composed of methanol-phosphate buffer pH 3 (30:70 v/v). Analytes were detected electrochemically. The quantification limit for metoclopramide in serum was 2 ng mL(-1). Linearity of the method was confirmed in the range of 5-120 ng mL(-1) (correlation coefficient 0.9998). Within-day relative standard deviations (RSDs) ranged from 0.3 to 5.5% and between-day RSDs from 0.8 to 6.0%. The analytical method was successfully applied for the determination of pharmacokinetic parameters after ingestion of 10 mg dose of metoclopramide. Studies were performed on 18 healthy volunteers of both sexes.

Preparation and in vivo evaluation of parenteral metoclopramide-loaded poly(alkylcyanoacrylate) nanospheres in rats

Metoclopramide-loaded poly(alkylcyanoacrylate) (PACA) nanospheres were prepared by emulsifier-free polymerization in aqueous media at ambient conditions. The optimum polymerization conditions for metoclopramide sorption on PACA nanospheres in the presence of dextran (DEX) or hydroxypropyl-beta-cyclodextran (HPCD) in the polymerization medium were studied and the feasibility of either poly(isobutylcyanoacrylate) (PIBCA) or poly(ethylcyanoacrylate) (PECA) nanospheres as parenteral prolonged release drug delivery system of metaclopramide in rats was also investigated. The optimum time for the addition of metaclopramide after initiating the polymerization was 1 h, which results in 14.8 +/- 0.4 and 9.2 +/- 0.5% of drug loading for PIBCA and PECA, respectively. The HPCD in the polymerization medium of PECA nanospheres improved the drug adsorption compared to DEX at all times, but the difference was only significant (p < 0.05) when metoclopramide was added at 0 and 30 min. Wistar rats were given subcutaneous (s.c.) injections of metoclopramide solution (5 mg/kg) and three different metoclopramide nanospheres suspensions (10 mg/kg) on two phases. The drug solution is rapidly absorbed, distributed, and eliminated. The maximum drug concentration was observed after 30 min of s.c. administration of all the tested nanosphere formulations. PECA-HPCD showed the highest concentration (3.16 +/- 0.66 mg/L) followed by PIBCA-DEX (1.95 +/- 0.37 mg/L) and PECA-DEX (1.68 +/- 0.28 mg/L). The AUCs of PECA-DEX, PECA-HPCD and PIBCA-DEX were 4.8, 1.88 and 2.43 times higher than that of the solution form, respectively. Following PECA-DEX the maximum drug concentration, 1.68 +/- 0.28 mg/L, rapidly decreased to 0.54 +/- 0.05 mg/L. The drug was successfully maintained around this serum drug concentration up to 12 h in rats and the mean drug concentration was reduced to 0.2 +/- 0.02 mg/L, 63% reduction, after 24 h of nanosphere administration. The developed aqueous parenteral prolonged release preparation (PECA-DEX) could be used as a promising intermittent formula for metoclopramide or other drugs when the oral route is not accessible, especially during managing chronic nausea in patients with advanced cancer.

Pharmacokinetics of metoclopramide in neonates

Despite its wide use as a prokinetic agent in neonates and infants with gastroesophageal reflux (GER), the pharmacokinetics of metoclopramide have not been characterized in this pediatric subpopulation. A single-dose pharmacokinetic study of oral metoclopramide (0.1 to 0.15 mg/kg) was performed in 10 fasted premature infants (weight 1.1 to 3.2 kg) ranging from 31 to 40 weeks postconceptional age. Metoclopramide was quantitated from repeated blood samples (n = 9 over 24 hours) by high-performance liquid chromatography. A one-compartment open model with first-order absorption best described the plasma concentration-time data. No correlations were observed between gestational, postnatal, or postconceptional age and any of the pharmacokinetic parameters studied. Comparison of the pharmacokinetic parameters from the study cohort and those reported previously from a similar study of older infants revealed no statistically significant differences. However, a prolonged apparent plasma clearance (Cl/F) of metoclopramide was observed in 30% of the infants studied, and the mean Cl/F and apparent steady-state volume of distribution (Vdss/F) were approximately 1.4- and 2.1-fold higher, respectively, than values reported in previous studies of metoclopramide disposition in adults. These data suggest that metoclopramide pharmacokinetics may exhibit a developmental dependency. Thus, a metoclopramide dose of 0.15 mg/kg given orally every 6 hours is recommended for the initiation of prokinetic therapy with this agent in infants who are < or = 31 weeks postconceptional age.

Metoclopramide plasma concentration in neonates

During the course of a multiple-dose metoclopramide (M) oral treatment, M plasma concentrations were measured just before (Cmin) and 1 hour after the administration (C1h) at steady-state in 5 (3 premature and 2 term) neonates. Mean Cmin was equal to 91.6 +/- 45.5 ng/ml and higher than C1h (87.4 +/- 43.2 ng/ml), but not significantly. A significant negative correlation was found between Cmin plasma concentration and gestational age as well as with postconceptional age, suggesting that the lower the gestational and postconceptional age, the lower the metoclopramide dosage should be.

Pharmacokinetic interaction between butorphanol nasal spray and oral metoclopramide in healthy women

The pharmacokinetics of butorphanol nasal spray, with and without the coadministration of metoclopramide, were studied in 24 healthy women. In this crossover study all volunteers received 3 treatments: a single, 1-mg dose of butorphanol nasal spray, a single, 10-mg oral dose of metoclopramide, and a combination of a single, 1-mg dose of butorphanol nasal spray and a single, 10-mg oral dose of metoclopramide. There was at least a one-week washout period between sessions. Serial blood samples were collected and plasma samples analyzed using a validated radioimmunoassay to determine the concentration of butorphanol, or a high-performance liquid chromatography/ultraviolet procedure was used to determine the concentration of metoclopramide. There were no statistically significant differences in the pharmacokinetic parameters, Cmax, tmax, AUC, and t1/2, for butorphanol with or without metoclopramide. Similarly, except for a delay in tmax of metoclopramide with coadministration of butorphanol, the pharmacokinetic parameters of metoclopramide were not significantly different between two treatments. Thus, the pharmacokinetics of both butorphanol and metoclopramide were not significantly altered when administered in combination. The incidence of nausea/vomiting after butorphanol administration was substantially reduced by coadministration of metoclopramide. Based on the pharmacokinetic and safety results, it can be concluded that butorphanol nasal spray and metoclopramide can be administered in combination without altering the dose regimen of either drug.

The quantitative effect of metoclopramide on abomasal and duodenal myoelectric activity of goats

Electromyographic (EMG) recordings of the abomasal corpus, pyloric antrum and proximal duodenum were made from six goats for 2 h periods before and after administration of 0.5 mg/kg metoclopramide intravenously or intramuscularly. Analog EMG signal was transformed via a computer program to digital data. The percentage change in electrical activity was determined by comparing the electrical activity following administration of IV or IM metoclopramide with the electrical activity of the control periods for the abomasal corpus, pyloric antrum and proximal duodenum. Metoclopramide caused a significant, time-dependent increase in duodenal electrical activity following either route of administration. This increase in duodenal electrical activity coincided with peak plasma levels of metoclopramide until its decline below 100 ng/ml in plasma. There was a significant biphasic increase in electrical activity of the abomasal corpus and pyloric antrum following IM administration of metoclopramide. The first phase lasted approximately 5 min and was followed by a longer period (approximately 20 min) of diminished electrical activity. A second phase of increased electrical activity occurred approximately 40-60 min after initial IM injection of metoclopramide. It is uncertain whether this increase was drug-mediated or endogenously-triggered. Similar increases in corpus and antral electrical activity were present following IV metoclopramide administration, though early increases were not statistically significant. Overall, the percentage changes in electrical activity correlated well with predicted peak plasma levels of metoclopramide only in the duodenum. This correlation was limited to approximately 5 min after IV and 15 min after IM metoclopramide administration.

Sustained-release metoclopramide plus methylprednisolone versus placebo plus methylprednisolone as antiemetic prophylaxis during non-cisplatin chemotherapy. A randomized double-blind cross-over trial

In a randomized double-blind cross-over trial, sustained-release metoclopramide (S) plus methylprednisolone (M) was compared with placebo (P) plus methylprednisolone as antiemetic prophylaxis during two cycles of non-cisplatin chemotherapy. S was administered as 60 mg every 12 h commencing on the evening before chemotherapy up to total of 300 mg metoclopramide in 2.5 days. Evaluation of nausea and vomiting was done by self-assessment schemes and visual analog scales. Fifty patients were included and 36 fulfilled both cycles. Mild nausea and vomiting were experienced by 81% and 83% in the S + M and P + M groups, respectively, while 42% and 39% showed complete control of nausea and vomiting during the first day of treatment. Moderate-dose S did not add to the antiemetic efficacy of M in non-cisplatin chemotherapeutic regimens.

A phase I/II evaluation of metoclopramide as a radiosensitiser in patients with inoperable squamous cell carcinoma of the lung

The feasibility of administering metoclopramide (MCA) as a radiosensitizer has been evaluated in 23 patients with a pathological or cytological diagnosis of a squamous cell carcinoma of the lung, clinically evaluated as inoperable. All patients received 40-60 Gy radiotherapy fractionated into 1.8 Gy fractions 5 times per week (Monday-Friday). Two MCA treatment regimens were used: (i) MCA at 2 mg/kg administered by intravenous-infusion 1-2 h prior to radiotherapy 3 times per week (Monday, Wednesday, Friday); and (ii) MCA at 1 mg/kg administered by intravenous infusion 1-2 h prior to radiotherapy 5 times per week (Monday-Friday). 11 of the 23 patients treated with radiotherapy and MCA had none to mild pneumonitis or fibrosis and another 8 of the 23 had moderate levels. No patient had their therapy interrupted due to radiation-related side-effects. The MCA-related side-effects were as expected, i.e. 78% of the patients experienced sedation/tiredness and 48% expressed restlessness/anxiety symptoms. Both the total dose and serum levels of MCA were significantly associated to the MCA side-effect profile. Tumour response, duration of tumour response and survival were significantly positively correlated to the total and weekly doses of MCA administered to the patients during their radiotherapy treatment. These favourable phase II data have justified the initiation of a phase II/III randomised multicentred trial being carried out in Europe to evaluate MCA as a radiosensitiser.

Comparative bioavailability of two tablet formulations of metoclopramide hydrochloride

This investigation was carried out to evaluate the bioavailability of a new tablet formulation of metoclopramide hydrochloride (10 mg), Metosil relative to a recognized product, Plasil BP. The two brands were found to be similar in assay and content uniformity and both met the BP requirements of disintegration time. The bioavailability was carried out on 18 healthy male volunteers who received a single dose (2 x 10 mg) of the test (T) and the recognized (R) products in a randomized balanced 2-way crossover design. After dosing, serial blood samples were collected for a period of 8 hours. Plasma harvested from blood was analyzed for metoclopramide by a sensitive and validated high-performance liquid chromatographic assay. The maximum plasma concentration (Cmax), area under the plasma concentration curve up to the last measurable concentration (AUC0-t), and to infinity (AUC0-00) were analyzed statistically under the assumption of a multiplicative model. The time to maximum concentration (Tmax) was analyzed assuming an additive model. The parametric confidence intervals (90%) of the mean values of the pharmacokinetic characteristics (AUC0-t AUC0-00 and Cmax) for T:R ratio were in each case well within the bioequivalence acceptable range of 0.8-1.25. The test formulation was found bioequivalent to the reference formulation by the Schuirmann's 2 one-sided t-tests and by Wilcoxon-Mann-Whitney 2 one-sided tests procedure. Therefore, the two formulations were considered to be bioequivalent.

Bioavailability and pharmacokinetics of metoclopramide in cattle

The bioavailability of metoclopramide was investigated in three steers following administration of 8 mg/kg by the oral, abomasal (cannula), and intravenous routes, using a Latin square design. The mean (+/- SD) oral and abomasal bioavailabilities were 51.3 +/- 30.7% and 76.2 +/- 15.5%, respectively. The mean value for clearance (Cl) was 20.1 +/- 5.9 ml/min and the volume of distribution (Vd) was 0.51 +/- 0.19 l/kg. Additional pharmacokinetic parameters for metoclopramide were determined following intravenous administration to seven cows. A predominate two-compartment model of distribution was found in six cows with a t 1/2 alpha harmonic mean of 24.2 min and a range of 11.2-72.4 min, a t 1/2 beta harmonic mean of 53.1 min and a range of 31.1-134.1 min, a Cl of 42.2 +/- 8.7 ml/min, and a Vd of 2.1 +/- 0.8 l/kg. To better define the relationship between metoclopramide concentration and release of prolactin, a treatment-by-subjects infusion study was conducted in which four different loading doses followed by constant infusion were used. A steady-state metoclopramide concentration (MCPss) of 8.8 +/- 2.6 ng/ml was associated with a three-fold elevation of prolactin to a mean value of 12.1 +/- 3.1 ng/ml in six yearling steers. Steady state serum prolactin concentrations (PRLss) did not rise significantly above 23.3 +/- 6.9 ng/ml, even when MCPss reached a concentration of 518.5 +/- 151.2 ng/ml. The short half-life, moderate Vd, low minimum pharmacologically effective concentration, and rapid Cl found for metoclopramide in cattle in this study, suggest that a continuous release device could potentially be useful in the application of this drug in the prevention and treatment of fescue toxicosis.

Determination of bioavailability and systemically available fractions of drugs undergoing reversible metabolism: application to 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2- (diethylamino)ethyl]benzamide and its sulfide and sulfone metabolites in rats

Methods are discussed which permit the calculation of the bioavailability (F) and fraction of an oral dose entering the central circulation (f) of a drug and its interconversion metabolite. The interrelationships between the F and f and between the F and systemically available fractions afforded by reversible metabolism are also derived and described. The application of these principles is illustrated by the pharmacokinetic analysis of 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2- (diethylamino)ethyl]benzamide (ML-1035, 1) and its sulfide (2) and sulfone (3) metabolites in rats. Like intravenous ML-1035, ML-1035 administered orally underwent metabolic interconversion with 2 but not with 3 in this species. Both ML-1035 and 2 were absorbed rapidly and are pharmacologically active. On average, 8.3 and 13% of an oral dose (152.4 mumol/kg) of ML-1035 were bioavailable as ML-1035 and its sulfide metabolite, respectively, while 23 and 65% of a molar equivalent dose of the sulfide metabolite were bioavailable as either compound, respectively. Thus, the sulfide metabolite is better absorbed than ML-1035 in rats. Following oral administration of either ML-1035 or 2, the systemically available fractions of both compounds were weakly to moderately influenced by the reversible metabolism process in rats. Moreover, the bioavailability of the sulfone metabolite was very poor (2.5-4%) following separate oral administration of ML-1035, 2, and 3.

Minimal biliary excretion and enterohepatic recirculation of metoclopramide in patients with extrahepatic cholestasis

The biliary excretion and apparent oral clearance of metoclopramide (MCL) were determined after oral administration of 1 mg MCL/kg body weight to 10 patients suffering from extrahepatic cholestasis with nasobiliary tube for drainage of the common bile duct. A bilioduodenal endoprosthesis was subsequently fitted in 6 of these patients, i.e. the enterohepatic circulation was restored, and the apparent oral clearance was re-determined. Biliary excretion, comprising free MCL and the products of conjugation, accounted for less than 1% of the administered dose. In accordance with this, the median areas under the plasma concentration-time-curves AUC(0-15 h) in patients with intact and interrupted enterohepatic recirculation were of similar size. The pharmacokinetic values in patients with cholestasis (median apparent oral clearance 0.5 l.kg-1.h-1; median t1/2 4.5 h) were similar to those previously reported in patients with healthy liver function. We conclude that it is not necessary to adjust single doses of MCL in patients recovering from obstructive jaundice.

Dose-response study of metoclopramide in gastroesophageal reflux in infancy

Twenty-four infants, 1 to 18 months-old, who were referred to four centers for suspected gastroesophageal reflux and whose esophageal pH after a standard formula meal given at 9 to 10 am (Ho-day 1) fulfilled the criterion of being < 4 for more than 5% of the time between H1 and H6, entered a double-blind placebo-controlled dose-response trial of metoclopramide (M). Twenty-four hours later (day 2), patients were randomly assigned to receive either placebo or a single 0.1, 0.2, or 0.4 mg/kg dose of metoclopramide, 30 min before the formula meal (n = 6/group) and the procedure was repeated. Metoclopramide plasma concentration was measured 1 h after dosing (C1h). On day 1, the time during which the esophageal pH was < 4 (time pH < 4), and five other parameters, were not significantly different in the treatment groups. On day 2, time pH < 4 (m(SD)) decreased from 33(13) to 30(33), 39(27), to 36(47), 42(15) to 18(13) and 48(25) to 31(46) min in the placebo, 0.1, 0.2, and 0.4 mg/kg metoclopramide groups, respectively. Possibly due to the large interindividual variability, no significant differences in parameters were observed between the different groups. None of the parameters correlated with the metoclopramide dose. Time pH < 4 expressed as the difference between day 1 and day 2, relative to day 1, decreased significantly as a function of C1h. No side effects were observed. A similar study should be performed after repeated dosing regimen.

Sex-differences in the disposition of substituted benzamides: pharmacokinetics of a gastroprokinetic agent (4-amino-5-chloro-2-[2- (methylsulfinyl) ethoxy]-N-[2-(diethylamino)ethyl] benzamide hydrochloride) (ML-1035) in male and female New Zealand white rabbits

The disposition of 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N- [2-(diethylamino)ethyl] benzamide hydrochloride (ML-1035) following intravenous (10 mg kg-1) and oral (200 mg kg-1) dosing was investigated in male and female New Zealand white rabbits. After intravenous dosing ML-1035 was eliminated with a half-life of 1.45 +/- 0.49 h in males and 0.79 +/- 0.08 h in females. Volume of distribution at steady-state was 2.08 +/- 0.98 l kg-1 in males and 9.11 +/- 5.86 l kg-1 in females. Clearance averaged 2.99 +/- 1.11 l h-1 kg-1 in males and 16.73 +/- 7.29 l h-1 kg-1 in females. All pharmacokinetic parameters were significantly different between males and females (p < 0.05). Absolute bioavailability after oral administration was 7.35 per cent for males and 12.31 per cent for females, suggesting that ML-1035 undergoes significant first-pass elimination. Plasma area under the curve for the metabolites of ML-1035 after both oral and intravenous administration were also different between the two sexes. These data suggest that the disposition of ML-1035 shows significant differences between male and female rabbits.

Determination of metoclopramide in the serum and urine of cattle

Metoclopramide, a dopamine-2 agent, has been shown to be useful in the antagonism of fescue toxicosis in grazing steers. The determination of this drug is described for the purpose of pharmacokinetic study and consideration of potential delivery devices to combat this economically significant condition.

Quantitation of a novel antiemetic (ADR-851) in plasma and urine by reversed-phase high-performance liquid chromatography with fluorescence detection

A sensitive and specific bioanalytical method for quantitation of a novel antiemetic (ADR-851) in plasma and urine has been developed and validated. The drug and internal standard (metoclopramide) are extracted from the plasma matrix by solid-phase extraction on cyanopropyl bonded-phase columns. After extraction, samples are separated by isocratic reversed-phase high-performance liquid chromatography. The parent drug, internal standard and a yet unidentified metabolite are detected by fluorescence. The method requires 1.0 ml of plasma or 0.1 ml of urine and has a lower limit of quantitation of 2 ng/ml with 10.9% relative standard deviation (R.S.D.). Method linearity has been established over a 2-800 ng/ml range when 1.0 ml of plasma is used. The intra- and inter-day imprecisions for the method are typically better than 6% and 11% R.S.D., respectively, in both plasma and urine over the entire dynamic range. The pooled estimate of bias is less than 5% and attests to the excellent accuracy.

Kinetics of intravenous metoclopramide in patients with hepatic cirrhosis

The pharmacokinetics of metoclopramide has been studied after acute IV administration to 12 patients with hepatic cirrhosis (6 with and 6 without ascites) and 6 control subjects. The elimination half-life was significantly longer in patients (11.4 h and 9.9 h in those with and without ascites, respectively, vs 6.4 h in controls). Total plasma clearance was significantly lower in patients (0.29 and 0.36 l.kg-1.h-1 vs 0.52 l.kg-1.h-1 in controls). The differences between patients with and without ascites did not reach statistical significance. Reduction of functional hepatic blood flow in cirrhotic patients is the probable cause of the observed alteration in metoclopramide kinetics.

Metoclopramide, domperidone and dopamine in man: actions and interactions

The effects of oral doses of the dopamine antagonist antiemetics metoclopramide and domperidone on baseline and dopamine stimulated renal function and systemic haemodynamics were assessed in a placebo controlled crossover study in 9 healthy volunteers. Metoclopramide did not change baseline ERPF, GFR or FF over 2 h post dosing but it significantly reduced baseline UNaV, UKV, urine flow, urinary dopamine excretion, supine and erect diastolic blood pressure and supine systolic blood pressure. Domperidone and placebo did not cause these effects. Metoclopramide caused a marked rise and domperidone a small fall in plasma aldosterone concentration (PAC) but placebo was without effect. Neither antiemetic altered plasma renin activity (PRA) but a small fall occurred with placebo. Two hours after pretreatment with placebo dopamine (2 micrograms/kg/min) increased effective renal plasma flow (ERPF), glomerular filtration rate (GFR), sodium excretion rate (UNaV), urine flow rate, urinary dopamine excretion rate, supine systolic blood pressure and supine and erect pulse rate and decreased the potassium excretion rate (UKV), filtration fraction (FF) and supine diastolic blood pressure. Metoclopramide pretreatment, did not attenuate the dopamine induced rise in ERPF, GFR, urine flow, urinary dopamine excretion or supine systolic blood pressure but it did attenuate the rise in pulse rate, the fall in diastolic pressure, and the antikaliuretic effect of dopamine leading to a net kaliuresis when compared to placebo. Domperidone was similar to placebo. Neither metoclopramide nor domperidone given orally caused clinically important antagonism of the renal haemodynamic effects of dopamine. However the effects of metoclopramide on blood pressure and electrolyte excretion may have clinical importance.(ABSTRACT TRUNCATED AT 250 WORDS)

High-dose metoclopramide + lorazepam versus low-dose metoclopramide + lorazepam + dehydrobenzperidol in the treatment of cisplatin-induced nausea and vomiting

In a randomized double-blind, cross-over trial of 34 patients receiving cisplatin-based chemotherapy (20-100 mg/m2), the antiemetic effect of high-dose metoclopramide (HDM) (10 mg/kg iv. loading dose + 7 hours continuous infusion) + lorazepam (L) (2.5 mg x 4 po) was compared with low-dose metoclopramide (LDM) (70 mg) + L (2.5 mg x 2 po) + dehydrobenzperidol (5 mg x 2 im). Among the 29 patients who completed the cross-over, HDM significantly reduced the number of vomiting episodes (p = 0.002) and the degree of nausea (p = 0.004). Seventeen patients preferred the HDM and 4 the LDM regimen (p = 0.01). Sedation was seen in all but 1 patient, and was graded as severe in 6 patients receiving the HDM and in 2 patients receiving the LDM regimen. No extrapyramidal adverse reactions were seen. We conclude that high-dose metoclopramide + lorazepam is a safe antiemetic regimen and significantly superior to low-dose metoclopramide + lorazepam + dehydrobenzperidol. Owing to the severe sedation which occurs in some patients, the dose of lorazepam should be individually adjusted.

Determination of ML-1035 enantiomers in plasma by chiral high-performance liquid chromatography

ML-1035, is a gastroprokinetic agent structurally related to metoclopramide. Because ML-1035 contains an asymmetric chiral sulphoxide moiety, a chiral HPLC method has been developed to separate and quantitate its R- and S-enantiomers in plasma. The ML-1035 enantiomers present in plasma are extracted with dichloroethane under alkaline conditions, the extract evaporated to dryness and reconstituted in the mobile phase. Samples are chromatographed on a Chiralcel OD HPLC column with hexane-absolute ethanol (1% TEA) (1:1, v/v) as the mobile phase. The enantiomers of the unchanged drug are determined by fluorescence measurement (ex: 310 nm, em: 350 nm). The method provides a linear response for both enantiomers over a concentration range of 25 (limit of determination) to 2500 ng ml-1 with correlation coefficients of 0.9987 or greater. The inter-assay precision is 9.5% or less and the accuracy ranges from 93.9 to 103.4% of the theoretical value. The method is used to determine the plasma concentrations of the R- and S-enantiomers following oral and intravenous administration of R- or S-enantiomers to dogs. The method is also adapted to measure enantiomer levels from in vitro reaction mixtures so that the possibility of metabolic inversion may be assessed. The data suggest that no significant level of inversion between the enantiomers occurred either in vivo or in vitro.

[Curative effect observation and plasma level determination in treating schizophrenia with the higher dose metoclopramide]

It is reported in this article that a good curative effect was obtained when 25 schizophrenia patients were treated with 572 +/- 174(mg/day) metoclopramide. The effective rate is 80%. The metoclopramide has a good effect to controlling excitation, hallucination, delusion and thinking disorder. By determination for the metoclopramide concentration in plasma, it is observed that the active concentration and toxic concentration is signification interrelated. The half-life period of the higher dose metoclopramide in the patients is 9.11 +/- 1.72 h.

[Treatment of nausea and vomiting induced by a 24-hour i.v. infusion of cisplatin]

Nine advanced gastric cancer patients were given 17 courses of cisplatin administrations by means of a 24-hour intravenous infusion at a dose of 100 mg/m2. For an anti-emetic, 40 mg of metoclopramide was administered 5 times at 6-hour intervals, along with a 500 mg hydrocortisone administration at the start of the cisplatin infusion. Despite this preventative treatment, nausea and/or vomiting occurred in over one-third of all the courses. Thus, to combat this nausea and/or vomiting, a combination of lorazepam (1.5 mg/day, divided into 3 p.o.), dexamethasone (20, 10 and 10 mg by i.v. at 3, 8, and 24 hours, respectively, after start of the cisplatin infusion), and a 60 mg intravenous administration of metoclopramide (5 times at 6-hour intervals) was given, and it was found that this new method (Method IV) prevented both nausea and vomiting.

A rapid liquid chromatographic method for the determination of metoclopramide in human plasma

A new sensitive analytical method is described for the measurement of metoclopramide in 1 ml plasma samples. The extraction step is followed by simple back-extraction and direct injection into the high-performance chromatographic (HPLC) column, with ultraviolet absorbance detection at 275 nm and reverse phase chromatography. The limit of detection for metoclopramide was 3 ng/ml and standard curves were linear over a concentration range of 5 to 1,000 ng/ml. The lowest quantifiable concentration of 5 ng/ml could be determined with a coefficient of variation of 6.5%. The method compares favourably with HPLC methods already described for metoclopramide and gives rapid and reproducible results in subjects receiving the drug.

An automated high-performance liquid chromatographic trace enrichment method for the determination of metoclopramide in serum and its application to a bioequivalence human volunteer study

An automated trace enrichment method for metoclopramide is described. Serum was injected on to a short column packed with PLRP-S 100A (a polymeric reversed-phase material). The unwanted components were washed off with borate buffer (pH 9.8) before switching to a Spherisorb ODS column for the separation. The limit of detection in serum samples was 2 ng/ml. The method was used in a pharmacokinetic study to compare the biovailability of two formulations of the drug.

Metoclopramide pharmacokinetics and pharmacodynamics in infants with gastroesophageal reflux

The pharmacokinetics and pharmacodynamics of metoclopramide oral solution were evaluated in six infants (0.9-5.4 months) with gastroesophageal reflux (GER) following the initial and 10th dose of 0.15 mg/kg administered every 6 h. Metoclopramide pharmacodynamics were assessed by pre- and post-dose comparison of esophageal pH monitoring data and clinical evaluation of improvement in GER symptoms. A significant reduction in the number of episodes of pH less than 4 for greater than 5 min and the longest episode of GER was seen between the predose and 10th dose (steady-state) evaluation periods. Four of the 6 patients had a 75% reduction in reflux time and demonstrated improvement in clinical symptoms by the 10th dose. Metoclopramide pharmacokinetics were best characterized by a one-compartment open model following the first and 10th doses. Metoclopramide serum concentrations (mean +/- SD) ranged from 56.2 +/- 23.5 to 32.7 +/- 13.2 ng/ml within a 6-h dosing interval at steady state. There were no significant differences between the first versus tenth dose values for Tmax (2.0 +/- 0.5 versus 2.2 +/- 0.4 h), Kel (0.14 +/- 0.03 versus 0.17 +/- 0.04 h-1), Vdarea (4.9 +/- 0.4 versus 4.4 +/- 0.6 L/kg), or clearance (0.66 +/- 0.16 versus 0.67 +/- 0.13 L/h/kg). The youngest subject (3.5 weeks) had a metoclopramide t 1/2 of 23.1 h following initial dose, which decreased to 10.3 h at steady-state. Care should be exercised in using the 0.15 mg/kg dose in infants less than 1 month of age as prolonged clearance may produce excessive serum concentrations.

Unaltered dopaminergic modulation of aldosterone secretion in cirrhosis

1. The responses of plasma aldosterone and plasma prolactin concentrations to metoclopramide (10 mg intravenously) were evaluated over 2 h in eight healthy controls and in 23 patients with cirrhosis (10 without and 13 with ascites). Plasma renin activity, glomerular filtration rate and renal sodium excretion were also determined. 2. Metoclopramide did not significantly influence plasma renin activity, whereas both plasma aldosterone and plasma prolactin rose significantly. The incremental areas under the curves did not differ among controls and cirrhotic patients without and with ascites. No significant correlations between plasma prolactin and aldosterone, either under basal conditions or after metoclopramide administration, were found in either controls or patients. 3. Glomerular filtration rate did not change after metoclopramide. Renal sodium excretion in controls and cirrhotic patients without ascites was also unaffected, whereas it decreased significantly in cirrhotic patients with ascites. In the latter, renal sodium excretion was inversely correlated with plasma aldosterone both under basal conditions and after metoclopramide administration. 4. The dopaminergic control of aldosterone secretion does not appear to be significantly altered in cirrhosis. Metoclopramide administration to cirrhotic patients with ascites leads to an increase in plasma aldosterone that may enhance renal sodium retention.

Examination of the correlation of serum metoclopramide levels with antiemetic efficacy in patients receiving cisplatin

The existence of a threshold serum metoclopramide level above which total protection from cisplatin-induced vomiting is more likely to occur has been proposed. We monitored serum metoclopramide levels prior to the third metoclopramide dose in the first cisplatin treatment cycle in patients receiving metoclopramide 2 mg/kg x 4 as part of a randomized double-blind cross-over study comparing single-agent metoclopramide with combination metoclopramide and dexamethasone. Serum samples from 35 patients (17 receiving single-agent metoclopramide and 18 receiving the combination) were analyzed using reverse-phase high-pressure liquid chromatography (HPLC). A wide variation in metoclopramide levels was observed (range 273-3380 ng/ml). Serum levels obtained from the same patient on multiple treatment cycles were well correlated, and the addition of dexamethasone did not alter serum metoclopramide levels. No threshold level could be identified for the two groups (single-agent or combination antiemetic therapy) considered individually or considered together. However, significantly more vomiting episodes and a lower incidence of total protection were noted in patients with metoclopramide levels above 1469 ng/ml receiving metoclopramide alone. This effect was nullified in the combination antiemetic group. Our data do not support a directly proportional relationship between serum metoclopramide level and antiemetic protection. However, a non-linear relationship with a possible agonist/antagonist effect is suggested.

Liquid chromatographic analysis of alizapride and metoclopramide in human plasma and urine using solid-phase extraction

A universal rapid, sensitive and selective high-performance liquid chromatographic method with UV detection at 230 nm has been developed for the determination of benzamide drugs in human plasma and urine. Sample pretreatment is carried out using solid-phase extraction columns, resulting in very high extraction recoveries of the compounds investigated (alizapride, metoclopramide, alpiropride, amisulpride). The detector response is linear from 25 to 10,000 ng/ml, and the detection limit is 3 ng/ml for alizapride and 10 ng/ml for metoclopramide. The proposed method is highly suitable for pharmacokinetic studies and for drug monitoring.

Determination of metoclopramide and its glucuronide and sulphate conjugates in human biological fluids (plasma, urine and bile) by ion-pair high-performance liquid chromatography

Metoclopramide was determined in human biological fluids (plasma, urine and bile) by reversed-phase ion-pair high-performance liquid chromatography using a newly introduced cyanopropyl column. The method is precise, selective and sensitive: the mean recoveries of metoclopramide from plasma, urine and bile were 74.4, 99.1 and 85.9%, respectively; the mean within- and between-run coefficients of variation were, respectively, 0.8 and 8.5% for plasma and 2.0 and 8.2% for urine at the drug concentration of 100 ng/ml, and 2.3 and 11.2% for bile at the concentration of 20 ng/ml; the lower detection limit was 2 ng/ml for 1 ml of each biological fluid. Enzymic hydrolysis of a urine or bile specimen was used in the identification of metoclopramide, as well as its glucuronide and sulphate conjugates, from the human samples. A preliminary study on metoclopramide determinations from plasma and urine samples of a healthy subject and from bile samples of a patient demonstrated the clinical applicability of the method for therapeutic monitoring and pharmacokinetic studies.

High-dose oral and intravenous metoclopramide in doxorubicin/cyclophosphamide-induced emesis. A randomized double-blind study

Emesis remains a major side effect of cancer chemotherapy. High-dose intravenous metoclopramide has proved to be effective antiemetic therapy for cisplatinum induced emesis. It has not been rigorously tested in nonplatinum chemotherapy. This double-blind, noncrossover, randomized trial compared high-dose oral and intravenous metoclopramide to standard oral prochlorperazine in emesis caused by doxorubicin [70 mg/m2 body surface area (BSA)] and cyclophosphamide (700 mg/m2 BSA). Prochlorperazine (10 mg/dose), oral metoclopramide, and intravenous metoclopramide (2 mg/kg/dose each) were given 30 min before chemotherapy and then every 4 h for 24 h. Ten patients were randomized to prochlorperazine therapy, 10 to oral metoclopramide, and 9 to i.v. metoclopramide. Median number of emeses for the first chemotherapy cycle was 3, 3, and 7 for prochlorperazine, oral, and i.v. metoclopramide, respectively. Statistical analysis showed no significant advantage of any regimen (p greater than 0.4). For patients who continued the antiemetic study, frequency of emesis increased with each successive cycle of chemotherapy. Six of 19 patients treated with metoclopramide developed dystonic reactions compared with zero of 10 on prochlorperazine. High plasma metoclopramide levels were achieved with both metoclopramide regimens and did not correlate with frequency of emesis. High-dose oral and i.v. metoclopramide in an every 4 h regimen did not show any advantage over standard antiemetic therapy for doxorubicin/cyclophosphamide-induced emesis and were associated with significant toxicity.

High-dose metoclopramide and chlorpromazine in the treatment of cisplatin-induced emesis

Twenty patients with lung cancer, treated with cisplatin and etoposide, were divided into two groups at random and given antiemetic therapy consisting of either high-dose metoclopramide (MCL) intravenously (8 mg/kg over 7 hours) and chlorpromazine (CPZ) (50 mg orally), or a reduced dose of MCL (6 mg/kg over 7 hours) and CPZ (50 mg orally). Serum MCL concentrations were monitored during the infusions. In the two groups, 33% and 38% vomited during and after the courses, and antiemetic control was achieved in 83% and 75% of the patients. There was no significant difference between the groups, and side effects were negligible. MCL concentrations exceeded 0.7 microgram/ml in all patients, with great inter-individual variation.

Bioavailability of controlled-release metoclopramide. 2nd communication: multiple dose study

The bioavailability of metoclopramide monochloride hydrate after oral multidose administration of controlled-release metoclopramide capsules (Gastro-Timelets) was compared with that of oral metoclopramide monochloride hydrate solution in 10 healthy men. 30 mg of each product was administered to each subject in a cross-over fashion for 5 consecutive days and the plasma metoclopramide concentration was measured using a HPLC assay. Peak plasma metoclopramide levels were lower, and occurred later after controlled-release capsules administration than after solution. The graphs representing plasma metoclopramide levels after controlled-release formulation were smooth and devoid of sharp peaks and troughs. The area under the plasma metoclopramide level-time curve (AUC) values showed that the products were bioequivalent with the mean AUC values for the capsule (0-24 h) 837.9 ng/h/ml and (120-150 h) 993.2 ng/h/ml; and for the solution (0-24 h) 878.8 ng/h/ml and (120-150 h) 1054.0 ng/h/ml.

Bioavailability of controlled-release metoclopramide. 1st communication: single dose study

The bioavailability of metoclopramide monochloride hydrate after single dose oral administration of a controlled-release capsule (Gastro-Timelets) was compared with that of oral metoclopramide monochloride hydrate solution in four normal volunteers. 30 mg of each product was administered to each subject in a cross-over manner on two separate occasions and plasma metoclopramide levels were measured using a HPLC method. Although peak plasma metoclopramide concentrations were lower, and occurred later after capsule treatment than after solution, analysis of the area under the plasma concentration-time curve (AUC) values for the two formulations demonstrated that the products were equivalent in terms of the extent of absorption, with the mean AUC value (0-30 h) for the capsule 943.7 ng/h/ml and that for the solution 896.2 ng/h/ml.

Metoclopramide suppositories in the treatment of diabetic gastroparesis

Gastroparesis diabeticorum is a common complication that develops in patients with diabetes mellitus. Although the pathogenesis remains unclear, the clinical symptoms of nausea, vomiting, and gastric dilatation frequently respond to metoclopramide hydrochloride, an agent that stimulates gastric emptying in addition to acting centrally as an antiemetic. Occasionally, patients are encountered whose severe gastroparesis is unresponsive to oral metoclopramide and who require intravenous therapy or drainage procedures (eg, pyloroplasty or gastrojejunostomy). Rectal administration of metoclopramide successfully controlled the clinical symptoms of gastroparesis diabeticorum in an outpatient after failure of oral dosing, thus avoiding the need for intravenous therapy. Gastric emptying studies and serum metoclopramide levels following a 25-mg rectal dose of metoclopramide hydrochloride verified the efficacy of therapy.

Pharmacokinetics and bioavailability of the anti-emetic agent bromopride

The pharmacokinetics of bromopride, an anti-emetic agent chemically related to metoclopramide, has been investigated in normal human subjects. After intravenous bolus doses of 10 mg, a one-compartment open model appeared adequate to describe the plasma drug concentration data. The systemic clearance of bromopride was 899 ml min-1 +/- 22 per cent CV, the volume of distribution was 2151 +/- 16 per cent CV, and the elimination half-life was 2.9 h +/- 21 per cent CV. Over a wide drug concentration range of up to 650 ng ml-1, bromopride was only 40 per cent bound to plasma proteins. The systemic availability of orally and intramuscularly administered solution doses of 20 mg of bromopride was 54 per cent and 78 per cent, respectively. Formulation of bromopride as the solid material in capsules delayed absorption but did not affect the extent of drug bioavailability. The pharmacokinetics of bromopride appeared similar to that of metoclopramide. No evidence for non-linear kinetics was found when bromopride was administered orally in the dose range 10-30 mg: after single oral doses of 10, 20, and 30 mg, peak mean plasma drug concentrations were 20 ng ml-1 +/- 32 per cent CV, 38 ng ml-1 +/- 16 per cent CV, and 64 ng ml-1 +/- 23 per cent CV, respectively.

Increased dopaminergic activity inhibits basal and metoclopramide-stimulated prolactin and thyrotropin secretion

The influence of physiological to pharmacological doses of dopamine (DA) on basal and metoclopramide (MTC)-stimulated PRL and TSH secretion was studied in 11 regularly menstruating women between days 3 and 8 of the cycle. In groups of 6, the women received 5-h infusions of either 5% glucose or DA in a solution of 5% glucose at a rate of 12-16 ml/h, adjusted according to weight. Infusion rates of DA were 0.04 microgram/kg . min (low), 0.4 microgram/kg . min (medium), and 4.0 micrograms/kg . min (high). After 3 h of infusion, 10 mg MTC were given iv. Blood samples were collected every 15 min from 1 h before to 2 h after the infusion, for a total of 8 h, for measurements of PRL and TSH. The mean serum PRL concentrations declined significantly (P less than 0.05) during DA infusions to nadir values of 62 +/- 5% (+/- SEM; low), 43 +/- 3% (medium), and 43 +/- 6% (high) of the basal levels, whereas basal TSH levels declined significantly, to 64 +/- 5% of basal levels (P less than 0.05), during both the medium and high dose DA infusions. On paired comparisons, the hormone responses to MTC were lower (P less than 0.05) during the infusion of high dose DA (PRL, 2286 +/- 495% vs. 891 +/- 328%; TSH, 100 +/- 43% vs. 60 +/- 15%), but were not changed when MTC was given during the low and medium doses of DA. A rebound phenomenon was found for PRL (P less than 0.05) after the medium and high doses of DA and for TSH (P less than 0.05) after the high dose. These results indicate that doses of DA considered physiological inhibit PRL and TSH secretion and larger doses inhibit their responses to the DA antagonist MTC.

Metoclopramide decreases renal plasma flow

Intravenous dopamine has been shown to increase renal plasma flow in man. The role of endogenous dopamine in the maintenance of renal plasma flow has not been described. We speculated that if endogenous dopamine activity is important in the maintenance of renal plasma flow, then high doses of a potent dopamine blocking drug such as metoclopramide would decrease renal flow. To test this hypothesis, we measured renal plasma flow using a single-injection technique with 131I-labeled orthoiodohippurate. Measurements were made before and after the administration of high doses of metoclopramide (1 to 2.5 mg/kg) to 20 patients receiving metoclopramide as an antiemetic before chemotherapy. Seven control subjects underwent sequential measurements of renal plasma flow without intervening metoclopramide dosing. Mean (+/- SD) renal plasma flow did not change in the control population (from 441 +/- 198 to 437 +/- 117 ml/min), but declined significantly in the patients who received metoclopramide (443 +/- 115 ml/min before metoclopramide and 387 +/- 137 ml/min after metoclopramide; P less than 0.001). In 25% of our study population the decline in renal plasma flow was greater than 20% below baseline levels. The magnitude of the effect did not appear to correlate with the pretreatment creatinine clearance, age, or sex of the patients. We conclude that high doses of metoclopramide decrease renal plasma flow in man. These data suggest a role for dopamine in the maintenance of renal plasma flow in patients receiving intravenous hydration. Changes of the magnitude we observed may well be of clinical importance. These findings therefore also suggest the possibility of metoclopramide potentiation of cisplatin nephrotoxicity.