Human Biodistribution and Radiation Dosimetry of the P-Glycoprotein Radiotracer [11C]Metoclopramide

Purpose

To assess in healthy volunteers the whole-body distribution and dosimetry of [¹¹C]metoclopramide, a new positron emission tomography (PET) tracer to measure P-glycoprotein activity at the blood-brain barrier.

Procedures

Ten healthy volunteers (five women, five men) were intravenously injected with 387 ± 49 MBq of [¹¹C]metoclopramide after low dose CT scans and were then imaged by whole-body PET scans from head to upper thigh over approximately 70 min. Ten source organs (brain, thyroid gland, right lung, myocardium, liver, gall bladder, left kidney, red bone marrow, muscle and the contents of the urinary bladder) were manually delineated on whole-body images. Absorbed doses were calculated with QDOSE (ABX-CRO) using the integrated IDAC-Dose 2.1 module.

Results

The majority of the administered dose of [¹¹C]metoclopramide was taken up into the liver followed by urinary excretion and, to a smaller extent, biliary excretion of radioactivity. The mean effective dose of [¹¹C]metoclopramide was 1.69 ± 0.26 μSv/MBq for female subjects and 1.55 ± 0.07 μSv/MBq for male subjects. The two organs receiving the highest radiation doses were the urinary bladder (10.81 ± 0.23 μGy/MBq and 8.78 ± 0.89 μGy/MBq) and the liver (6.80 ± 0.78 μGy/MBq and 4.91 ± 0.74 μGy/MBq) for female and male subjects, respectively.

Conclusions

[¹¹C]Metoclopramide showed predominantly renal excretion, and is safe and well tolerated in healthy adults. The effective dose of [¹¹C]metoclopramide was comparable to other ¹¹C-labeled PET tracers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11307-021-01582-4.

Influence of Cation Transporters (OCTs and MATEs) on the Renal and Hepatobiliary Disposition of [11C]Metoclopramide in Mice

PURPOSE

To investigate the role of cation transporters (OCTs, MATEs) in the renal and hepatic disposition of the radiolabeled antiemetic drug [11C]metoclopramide in mice with PET.

METHODS

PET was performed in wild-type mice after administration of an intravenous microdose (<1 μg) of [11C]metoclopramide without and with co-administration of either unlabeled metoclopramide (5 or 10 mg/kg) or the prototypical cation transporter inhibitors cimetidine (150 mg/kg) or sulpiride (25 mg/kg). [11C]Metoclopramide PET was also performed in wild-type and Slc22a1/2(-/-) mice. Radiolabeled metabolites were measured at 15 min after radiotracer injection and PET data were corrected for radiolabeled metabolites.

RESULTS

[11C]Metoclopramide was highly metabolized and [11C]metoclopramide-derived radioactivity was excreted into the urine. The different investigated treatments decreased (~2.5-fold) the uptake of [11C]metoclopramide from plasma into the kidney and liver, inhibited metabolism and decreased (up to 3.8-fold) urinary excretion, which resulted in increased plasma concentrations of [11C]metoclopramide. Kidney and liver uptake were moderately (~1.3-fold) reduced in Slc22a1/2(-/-) mice.

CONCLUSIONS

Our results suggest a contribution of OCT1/2 to the kidney and liver uptake and of MATEs to the urinary excretion of [11C]metoclopramide in mice. Cation transporters may contribute, next to variability in the activity of metabolizing enzymes, to variability in metoclopramide pharmacokinetics and side effects.

Anticholinergic Load and Nutritional Status in Older Individuals

OBJECTIVES

The association between anticholinergic load-based Anticholinergic Risk Scale scores and nutritional status is unclear in Japanese patients. The aim of this study was to establish whether anticholinergic load affects the nutritional status of geriatric patients in convalescent stages.

DESIGN

Retrospective longitudinal cohort study.

SETTING

Convalescent rehabilitation wards.

PARTICIPANTS

Of the 1490 patients aged ≥65 years who were discharged from convalescent rehabilitation wards between July 2010 and October 2018, 908 patients met the eligibility criteria. They were categorized according to the presence or absence of increased anticholinergic load from admission to discharge.

MEASUREMENTS

Demographic data, laboratory data, the Functional Independence Measure were analyzed between the groups. The primary outcome was Geriatric Nutritional Risk Index (GNRI) at discharge. Multiple linear regression analysis was performed to analyze the relationship between anticholinergic load and GNRI at discharge.

RESULTS

Multiple linear regression analysis after adjusting for confounding factors revealed that anticholinergic load was independently and negatively correlated with GNRI at discharge. Particularly, the use of chlorpromazine, hydroxyzine, haloperidol, metoclopramide, risperidone, etc. increased significantly from admission to discharge.

CONCLUSION

Increased anticholinergic load during hospitalization may be a predictor of nutritional status in geriatric patients.

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.

Should we stop prescribing metoclopramide as a prokinetic drug in critically ill patients?

Regulatory agencies in North America and Europe recently re-evaluated the safety of metoclopramide. This re-evaluation resulted in recommendations and restrictions in order to minimise the risk of neurological and other adverse reactions associated with the use of metoclopramide. In the ICU, off-label prescription of metoclopramide is common. We have reviewed the evidence for safety, effectiveness and dosing of metoclopramide in critically ill patients. Furthermore, tachyphylaxis is addressed and alternatives are summarised. Finally, recommendations are presented not to abandon use of metoclopramide in ICU patients, because metoclopramide is considered effective in enhancing gastric emptying and facilitating early enteral nutrition.

Effect of metoclopramide on the excretion rate of paracetamol using HPLC-DAD

A simple, precise, accurate and robust high-performance liquid chromatography assay was developed and validated for the simultaneous analysis of metoclopramide and paracetamol in human urine. The drugs were isolated from urine samples by solid-phase extraction using C8 cartridges, then analyzed on a C18 reversed-phase column using a mixture of aqueous phase (water containing 0.2% TEA adjusted to pH 3 using ortho-phosphoric acid) and methanol in a ratio of 80:20 (v/v). The method was found to be linear for both drugs in a concentration range of 0.5 to 160 µg/mL using a concentration of 10 µg/mL of internal standard (theophylline) in urine samples (r > 0.999). The accuracy of the method was higher than 91.73% (percentage of the grand mean of recoveries) and the precision was lower than 3.4% (overall percentage of relative standard deviation) for both metoclopramide and paracetamol. The method was applied to the determination of the drugs in urine samples obtained from male volunteers, following the administration of two formulations, one containing paracetamol alone (Paracetamol(®)) and the other containing a mixture of paracetamol and metoclopramide (Migracicid(®)). Determination of the drugs was conducted and the effect of increasing the rate of absorption, consequently increasing the mean urinary excretion of paracetamol due to the presence of metoclopramide in the pharmaceutical formulation, was recorded.

Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studies

Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was peformed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (dvs) in the range of about 3–10 μm. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1–3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug.

Evidence of lowest brain penetration of an antiemetic drug, metopimazine, compared to domperidone, metoclopramide and chlorpromazine, using an in vitro model of the blood–brain barrier

PURPOSE

The objective of the current study was to determine the ability of some antiemetic compounds to cross the blood-brain barrier (BBB) and thereby to determine possible side effects of compounds for the central nervous system (CNS).

METHODS

We compared the brain penetration of some antiemetic compounds using an in vitro BBB model consisting in brain capillary endothelial cells co-cultured with primary rat glial cells.

RESULTS

This study clearly demonstrated that the metopimazine metabolite, metopimazine acid, has a very low brain penetration, lower than metopimazine and even less than the other antiemetic compounds tested in this study.

CONCLUSIONS

The poor brain penetration of metopimazine acid, metopimazine biodisponible form, seems very likely related to the clinically observed difference in therapeutic and safety profile.

Sustained release of hydrophobic and hydrophilic drugs from a floating dosage form

Floating dosage forms enable the sustained delivery of drugs in the gastro-intestinal tract. In this study, a type of multi-unit floating gel bead was synthesized with calcium alginate, sunflower oil, and a drug of interest through an emulsification/gelation process. The alginate beads with oil addition were able to continuously float over the medium for 24h under constant agitation while the non-oily beads could not. Three kinds of drugs with different hydrophilicities, ibuprofen, niacinamide and metoclopramide HCl, were tested in the study. The hydrophobic drug ibuprofen was released in a sustained manner for 24h, due to the oil partitioning. With suitable modification, the beads were able to also release the hydrophilic drugs, niacinamide and metoclopramide HCl, for a similar duration. Therefore a floating dosage form that is able to sustain release both hydrophobic and hydrophilic drugs within its extended gastric retention time has been developed.

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).

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.

Effect of Anticholinergics (Atropine, Glycopyrrolate) and Prokinetics (Metoclopramide, Cisapride) on Gastric Motility in Beagles and Labrador Retrievers

The effect of atropine, glycopyrrolate, metoclopramide and cisapride on the antral motility was investigated in eight dogs (four Beagles and four Labradors) using passive telemetry. Both anticholinergics induced a pronounced and lasting reduction of the intensity and frequency of the contractions. A definite dose-related inhibition of the antral motility was seen in Beagles, similar for both active substances. Low doses of atropine (0.02 mg/kg BW i.m.) and glycopyrrolate (0.005 mg/kg BW i.m.) completely inhibited the gastric motility for at least 30 min, whereas higher doses (0.04 or 0.01 mg/kg BW) caused a cessation of activity for more than 3 h. In Labradors, the effects of both active substances were not so dose related and the effect of glycopyrrolate lasted at least 6 h, whereas the effect of atropine gradually decreased after 3 h. A distinct breed difference regarding the effect of the two prokinetics on the antral motility was also observed. In Beagles, the prokinetics, at a low dose (metoclopramide 0.3 mg/kg BW, cisapride 0.2 mg/kg BW), resulted in a significant increase in the amplitude integral. Higher doses (metoclopramide 0.6 mg/kg BW, cisapride 0.5 mg/kg BW) also increased the integrals of the pressure profiles, but significantly less than with the lower doses. In Labradors, both medications, mainly at higher doses, resulted in an increase of the contraction amplitudes. The low dose had no (cisapride) or only a transient effect (metoclopramide). The frequency of the antral contractions was not at all influenced by cisapride, and only in Beagles metoclopramide resulted in a dose-related increase. It is not clear if the different results in Labradors and Beagles are because of breed or body weight.

Pharmacokinetic interaction between fluoxetine and metoclopramide in healthy volunteers

The pharmacokinetic interaction of fluoxetine with metoclopramide in healthy volunteers was evaluated. A dose of 20 mg metoclopramide in combination with 60 mg fluoxetine was administered to 24 healthy male volunteers in a two treatment study design, separated by 8 days in which the fluoxetine alone was administered as a single p.o. dose daily. Plasma concentrations of metoclopramide were determined during a 24 h period following drug administration. Metoclopramide plasma concentrations were determined by a validated HPLC method. Pharmacokinetic parameters of metoclopramide were calculated using non-compartmental analysis. In the two periods of treatment, the mean peak plasma concentrations (Cmax) were 44.02 ng/ml (metoclopramide alone) and 62.72 ng/ml (metoclopramide after pre-treatment with fluoxetine). The times taken to reach Cmax and tmax, were 1.15 h and 1.06 h, respectively. The total areas under the curve (AUC(0-infinity)) were 312.61 ng.h/ml and 590.62 ng.h/ml, respectively. The half-life values (t1/2) were 5.52 h and 8.47 h. Statistically significant differences were observed for both AUC(0-infinity) and t1/2 of metoclopramide when administered alone or after 8 days treatment with fluoxetine. The experimental data demonstrate the pharmacokinetic interaction between fluoxetine and metoclopramide and suggest that the observed interaction may be clinically significant, but its relevance has to be confirmed.

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.

Pro-kinetic medications as aids in imaging the small bowel by video-capsule

The m2a wireless video-capsule (Given Imaging Ltd., Israel) is a miniature ingestible camera utilized for the color imaging of the small intestine walls. Despite its diagnostic yield superiority over all other diagnostic modalities, a substantial part of the pathologies are not spotted. Considering the transmitted pictures high quality a resolution problem is ruled out, but rather it is assumed that parts of the intestinal wall surface are missed in the imaging process. Another important problem is the difficulty encountered by the capsule in crossing the antro-duodenal junction, probably due to pyloric hypomotility. Pro-kinetic drugs are capable of increasing the small intestine peristaltic wave velocity and contractile amplitude, thus assisting the video-capsule movements and widening the camera photo arc. The arc width is directly proportional to the surface imaging capacity. A specific dose range (cisapride 25-30 mg, metoclopramide 30 mg approximately) is calculated and an analysis is made of the use of these pro-kinetic drugs to increase the device diagnostic yield. It should be emphasized that: (1) despite a potential risk for complications, such as bleeding from small intestine lesions, radiological studies underline the high safety profile of metoclopramide; (2) increased capsule speed of progress is not expected to cause a loss of imaged area; (3) an oral dose below 15 mg (metoclopramide or cisapride) may not suffice to accelerate the capsule transit through the antro-duodenal junction. The concept is patent protected.

Maternal medication causing drug dystonia in a newborn: placental transfer of drugs

Dystonia is a movement disorder characterized by sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. Drug-induced dystonia may occur within minutes or hours of exposure to an inciting drug; it is seen with familial pattern and cannot be correlated with blood level of the drug.

[Incidence of pain upon injection of a new formula of propofol in a fat emulsion of medium- and long-chain triglycerides]

OBJECTIVE

To study the incidence of pain upon injection of 1% propofol (Propofol-Lipuro 1%, B. Braun, Melsungen, Germany) in a 10% fat emulsion containing equal proportions (50:50) of medium- and long-chain triglycerides.

PATIENTS AND METHODS

The subjects were 600 adult patients scheduled for elective surgery. The use of premedication was left to the discretion of the anesthesiologist. All patients received the study anesthetic injected slowly (20-40 mg per 10 seconds) at a dose of 1.5 to 2.5 mg/Kg. Variables recorded were incidence and type of pain upon administering the anesthetic, the patients' clinical characteristics, premedication administered, and method of venous puncture. Bivariate and multivariate statistical analyses were performed to determine factors associated with the appearance of pain.

RESULTS

The overall incidence of pain upon administration of propofol-lipuro was 27%. Pain was moderate to intense in 9%. Premedication did not affect the incidence of pain with injection. The risk factors that predicted the appearance of pain were injection through a small-caliber catheter (> 18 G) and injection on the dorsal hand (P < 0.05).

CONCLUSIONS

The incidence of pain upon injection of propofol-lipuro is low in comparison with incidence rates reported in the literature for the traditional formula, but administration of the fat emulsion formula through a vein on the dorsal side of the hand or through a venous catheter smaller than 18 G should be avoided. Double-blind randomized controlled trials should be conducted to clarify the advantages that propofol-lipuro seems to offer.

Mucoadhesive Delivery Systems. II. Formulation and In‐Vitro/In‐Vivo Evaluation of Buccal Mucoadhesive Tablets Containing Water‐Soluble Drugs

From the previous work (Part I), mucoadhesive formulae containing 5% CP/65% HPMC/30% lactose and 2% PC/68% HPMC/30% mannitol as well as formulae based on sodium carboxymethyl cellulose (SCMC) were selected. Medicated tablets were prepared using diltiazem hydrochloride (DZ) and metclopramide hydrochloride (MP) in two different doses (30 and 60 mg). The effect of drug and dose on the mucoadhesive properties and in-vitro drug release was evaluated. All formulae produced extended drug release (over 8 to 12 h). Polyacrylic acid based matrices (PAA) showed Fickian's diffusion release pattern for both drugs. SCMC ensured zero-order release for DZ, which deviated to anomalous behavior in case of MP. Doubling the dose significantly reduced the bioadhesion strength (p<0.05) with a slight improvement in drug release rate. The formulation of bilayer tablets containing drug-free layer and medicated layer enhanced the drug release without affecting the bioadhesive performance. The bilayer tablet formulated with 2% PC/68% HPMC/30% mannitol (PC2) was selected for studying the in-vivo metoclopramide release in four healthy volunteers. The tablet ensured controlled drug release for 12 h, in addition, good correlation (r=0.9398) was observed between in-vitro and in-vivo data. The effect of ageing on selected formulae containing DZ and MP, respectively, was studied. Storage at 40 degrees C and 75% relative humidity for 6 months didn't influence the mucoadhesive performance, however, an enhanced released rate was observed.

Pharmacokinetic interaction study between ranitidine and metoclopramide

The pharmacokinetics of metoclopramide in healthy volunteers was evaluated to determine if previously repeated doses of ranitidine inhibit the metabolism of the gastrointestinal prokinetic drug. Metoclopramide 20 mg (tablets) in combination with ranitidine 150 mg (tablets) were administered to 14 healthy human volunteers in a two treatment study design, separated by 5 days in which the ranitidine alone was administrated in single p.o. doses twice daily. Plasma concentrations of metoclopramide were determined during a 24 hour period following drug administration. Metoclopramide plasma concentrations were determined by a validated RP-HPLC method. Pharmacokinetic parameters were calculated with compartmental and non-compartmental analysis. In the two periods of treatments, the mean peak plasma concentrations Cmax were 44 ng/ml (metoclopramide alone) and 49.2 ng/ml (metoclopramide and ranitidine). The time taken to reach the peak, Tmax, was 1.15 hrs, and 1.21 hrs, respectively. The total areas under the curve (AUC) was 314.3 ng.hr/ml and 354.06 ng.hr/ml, respectively. The half-life (T 1/2) was 5.6 hr and 6.7 hr. A statistically significant difference was observed for both AUC and half-life of metoclopramide when administered alone or after 5 days of treatment with ranitidine. The experimental data proved the pharmacokinetic interaction between ranitidine of metoclopramide, and suggest monitoring adverse effects in patients.

Drug release from injectable depots: two different in vitro mechanisms

Certain poly (lactide-co-glycolide) (PLGA)/benzyl benzoate (BB) solutions can form gels when injected into buffer (depot formation) as well as upon ageing under ambient conditions. When evaluating various PLGAs in benzyl benzoate, we have found that only those that gel upon ageing also form gel depots in buffer. This indicates that depot formation in this system may be fundamentally different from the phase inversion depot formation that has been observed for PLGA in water-miscible solvents. The drug release kinetics in vitro is controlled both by diffusion and erosion, with the base form of the drug being always released faster than its salt form. This is due to base-catalyzed hydrolysis. While gel permeation chromatography (GPC) measurements show a continuous decrease in molecular weight, the rheological properties upon buffer injection show maxima, for the base drug and the salt drug. The location of the viscosity maximum with time is dependent on the nature of the drug and its concentration.

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.

Controlled delivery of metoclopramide using an injectable semi-solid poly(ortho ester) for veterinary application

In animal health care, current therapeutic regimens for gastrointestinal disorders require repeated oral or parenteral dosage forms of anti-emetic agents. However, fluctuations of plasma concentrations produce severe side effects. The aim of this work is to develop a subcutaneous and biodegradable controlled release system containing metoclopramide (MTC). Semi-solid poly(ortho ester)s (POE) prepared by a transesterification reaction between trimethyl orthoacetate and 1,2,6,-hexanetriol were investigated as injectable bioerodible polymers for the controlled release of MTC. MTC is present in the polymeric matrix as a solubilised form and it is released rapidly from the POE by erosion and diffusion because of its acidic character and its high hydrosolubility. If a manual injection is desired, only low molecular weight can be used. However, low molecular weight POEs release the drug rapidly. In order to extend polymer lifetime and decrease drug release rate, a sparingly water-soluble base Mg(OH)(2) was incorporated to the formulation. It was possible to produce low molecular weight POE that can be manually injected and releasing MTC over a period of several days.

Effects of acute moderate hypoxemia on kinetics of metoclopramide and its metabolites in chronically instrumented sheep

Hypoxemia is known to induce various physiological changes which can result in alteration in drug pharmacokinetics. To examine the effect of acute moderate hypoxemia on metoclopramide (MCP) pharmacokinetics, a continuous 14-hour infusion of MCP during a normoxemic, hypoxemic and subsequent normoxemic period was conducted in eight adult sheep. Arterial blood and urine samples were collected to examine the effects on the pharmacokinetics of MCP and its deethylated metabolites. MCP and its mono- and di-deethylated metabolites were quantitated using a GC/MS method. Steady-state concentrations of MCP were achieved in each of the three periods. During hypoxemia, MCP plasma steady-state concentration increased significantly from 50.72 +/- 1.06 to 63.62 +/- 1.79 ng/mL, and later decreased to 55.83 +/- 1.15 ng/mL during the post-hypoxemic recovery period. Total body clearance (CL(TB)) of MCP was significantly decreased from 274.2 +/- 48.0 L/h to 205.40 +/- 28.2 L/h during hypoxemia, and later restored to 245.8 +/- 44.2 L/h during the post-hypoxemic period. Plasma mono-deethylated MCP concentration (32.78 +/- 1.73 ng/mL) also increased, compared to the control group (21.20 +/- 1.39 ng/mL), during hypoxemia and subsequent normoxemic period. Renal excretion of MCP and its metabolites was also decreased during hypoxemia, while urine flow was increased with a concomitant decrease in urine osmolality. Thus, the results indicate that acute moderate hypoxemia affects MCP pharmacokinetics.

Analysis of formulation and food effect on the absorption of metoclopramide

OBJECTIVES

Assessment of the relative and absolute bioavailability of immediate release and sustained release formulations of metoclopramide. Assessment of the effect of a high-fat meal on the pharmacokinetics of sustained release metoclopramide.

MATERIAL AND METHODS

In a balanced 4-way crossover study in 16 healthy male volunteers, a sustained release (SR) formulation of metoclopramide was compared with a solution for injection (A) and an immediate release tablet (B). The SR formulation was administered after a fasting period (C) as well as after a high-fat meal (D). A single dose of 30 mg metoclopramide was investigated in each treatment. Metoclopramide concentrations were determined by HPLC.

RESULTS

The absolute bioavailability of the sustained release formulation (fasting state) was 58% and thus about 17% lower than the bioavailability of the immediate release formulation. Comparing the treatments C (sustained release, fasting state) and D (sustained release, high-fat meal) no significant influence of food on the absorption of sustained release metoclopramide could be detected.

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.

Sustained release microspheres of metoclopramide using poly(D,L-lactide-co-glycolide) copolymers

Metoclopramide was encapsulated with poly(D,L-lactide co glycolide) copolymers of different molecular weights using the emulsification/solvent evaporation technique. These polymers included poly(D,L-lactide-co-glycolide) 50:50 with inherent viscosity (i.v.) 0.2, and average molecular weight 8000, poly(D,L-lactide-co-glycolide) 50:50 with i.v. 0.8 and average molecular weight 98000 and poly(D,L-lactide-co-glycolide) 85:15 with i.v. 1.4 and average molecular weight 220000. The effect of the polymers' molecular weights as well as the polymer-to-drug ratios on the yield, the particle size distribution, and the drug content of the microspheres was investigated. The release rate of the drug was studied for 96 h in a phosphate buffer of pH 7.4. The study also investigated the effect of the new poly(lactide-co-glycolide)-H series on the characteristics of the prepared microspheres. Data revealed that a higher yield was obtained with polymers of lower molecular weights. A lower yield was also obtained with increasing the drug-to-polymer ratios for all the investigated polymers. The drug content of the microspheres was lower than expected, ranging from 49-85%, which suggested a chemical interaction between the drug and the polymers, as proved by differential scanning calorimetry (DSC) and infra red (IR) studies. A higher interaction was obtained with the H-series of the copolymers. The release of the drug mainly followed zero order kinetics on increasing either the polymers' molecular weights or the polymer-to-drug ratios. Diffusion kinetics was observed only with those batches prepared with low polymer-to-drug ratios. The release rate was a function of both the polymers' molecular weights and the drug-to-polymer ratios.

Formulation optimization of controlled-release pellets of metoclopramide hydrochloride using dissolution fit factor approach

The purpose of this study was to optimize the formulation variables for the preparation of ethyl cellulose-coated nonpareils loaded with metoclopramide hydrochloride (MCL). The approach to evaluate the effectiveness of formulation parameters was monitored by release rate testing using dissolution fit factors as a tool. The content of ethyl cellulose used in the formulation was based on the drug-loaded weight. The interrelationship of each developed formulation and the reference formulation Gastro-Timelets and their respective dissolution curves were evaluated using Moore's equation: [equation: see text]. The relationship between the ethyl cellulose content in the formulation and the dissolution fit factor f2 can be described as the following regression equation: Y = -0.054X2 + 3.347X - 1.915 (r2 = 0.99). The optimum ethyl cellulose content obtained from the equation was 30.8%. The type and content of plasticizer used in the formulation to achieve the greatest f2 were determined to be Myvacet 9-40 at the concentration of 25%. Results indicated that using the release rate testing approach with the dissolution fit factor as a tool could provide valuable information for formulation optimization.

Controlled release of solid-reversed-micellar-solution (SRMS) suppositories containing metoclopramide-HCl

The investigated drug delivery system is a solid-reversed-micellar-solution (SRMS). The composition of this solution is 70% Witepsol W35 and 30% (w/w) lecithin. 1% (w/w) metoclopramide-HCl (MCP) was solubilized in the SRMS. After melting and on contact with water or any physicological aqueous media the SRMS exhibits an application induced transformation into a semisolid system of liquid crystalline microstructure. The structure of the liquid crystal has been identified by polarized light microscopy as a lamellar mesophase. Due to a low coefficient of diffusion in this mesophase a controlled release of the drug may be possible. The release profiles of the in vitro experiments have shown zero order kinetics and a sustained release of the SRMS-suppositories (SRMS-supp.) in comparison with commercial suppositories (Gastrosil-supp.). To examine bioavailability an in vivo study with rabbits was carried out. Five SRMS-supp. (10 mg MCP) and five Gastrosil-supp. (10 mg MCP) were tested in a parallel-group study. These experiments have shown a five times longer mean residence time (parameter of sustained release) in comparison with Gastrosil-supp. In vitro and in vivo studies have shown that rectal application of SRMS-supp. provides an appropriate route for controlled release of MCP via application induced transformation into liquid crystals.

Sequential single doses of cisapride, erythromycin, and metoclopramide in critically ill patients intolerant to enteral nutrition: a randomized, placebo-controlled, crossover study

OBJECTIVE

To evaluate the comparative efficacy of enteral cisapride, metoclopramide, erythromycin, and placebo for promoting gastric emptying in critically ill patients with intolerance to gastric enteral nutrition (EN).

DESIGN

A randomized, crossover study.

SETTING

Adult medical intensive care unit at a university-affiliated private hospital and trauma intensive care unit at a university teaching hospital.

PATIENTS

Ten adult, critically ill, mechanically ventilated patients not tolerating a fiber-containing EN product defined as a single aspirated gastric residual volume >150 mL or two aspirated gastric residual volumes >120 mL during a 12-hr period.

INTERVENTIONS

Patients received 10 mg of cisapride, 200 mg of erythromycin ethylsuccinate, 10 mg of metoclopramide, and placebo as 20 mL of sterile water every 12 hrs over 48 hrs. Acetaminophen solution (1000 mg) was administered concurrently. Gastric residual volumes were assessed, and plasma acetaminophen concentrations were serially determined by TDx between 0 and 12 hrs to evaluate gastric emptying.

MEASUREMENTS AND MAIN RESULTS

Gastric residual volumes during the study were not significantly different between agents. No differences in area under the concentration vs. time curve or elimination rate constant were identified between agents. Metoclopramide and cisapride had a significantly shorter mean residence time of absorption than erythromycin (6.3+/-4.5 [SEM] mins and 10.9+/-5.8 vs. 30.1+/-4.5 mins, respectively [p<.05]). Metoclopramide (9.7+/-15.3 mins) had a significantly shorter time to peak concentration compared with erythromycin and placebo (60.7+/-8.1 and 50.9+/-13.5 mins, respectively [p<.05]). The time to onset of absorption was significantly shorter for metoclopramide vs. cisapride (5.7+/-4.5 vs. 22.9+/-5.7 mins [p<.05]).

CONCLUSION

In critically ill patients intolerant to EN, single enteral doses of metoclopramide or cisapride are effective for promoting gastric emptying in critically ill patients with gastric motility dysfunction. Additionally, metoclopramide may provide a quicker onset than cisapride.

Effect of transdermal iontophoresis codelivery of hydrocortisone on metoclopramide pharmacokinetics and skin-induced reactions in human subjects

The effects of transdermal iontophoresis (IP) codelivery of hydrocortisone (HC) on metoclopramide hydrochloride (MCP) pharmacokinetics and on skin-induced reactions were evaluated in a randomized, crossover clinical study. MCP, an antiemetic, low molecular weight, cationic drug intended for systemic delivery, was delivered from the anode of IP systems at a constant current of 100 microA/cm(2). HC, a neutral endogenous antiinflammatory agent, was codelivered from the same electrode, primarily by electroosmotic processes. Each subject (n = 7) wore two identical IP systems (MCP alone or MCP plus HC), each supplying 500 microA, one on each upper arm for 4 h. One week later, each subject repeated the procedure with the alternate type of MCP system. HC did not change the pharmacokinetics of MCP: There were no statistically significant differences in MCP plasma concentrations, half-life, area under the curve (AUC), or rate of absorption between the two treatment groups. However, HC significantly decreased erythema and edema scores produced by the IP of MCP. In both groups, a steady-state MCP flux of about 100 microg/(cm(2) x h) was achieved after only 1 h of transport, and input rate dropped dramatically immediately after removal of the system. In vitro, HC flux through human epidermis from an MCP plus HC formulation was 2.8 +/- 1.1 microg/(cm(2) x h) after 4 h transport at 100 microA/cm(2), suggesting negligible systemic exposure to hydrocortisone. These data indicate that MCP input rate and its clearance from the skin are unaltered by HC and that the codelivery of HC by IP is an effective strategy for inhibition of local reactions resulting from the transdermal delivery of drugs.

Evaluation of prochlorperazine buccal tablets (Bukatel) and metoclopramide oral tablets in the treatment of acute emesis

The dizziness associated with vertiginous disorders is often accompanied with nausea and/or vomiting. Antiemetic effect of prochlorperazine (PCZ) is diminished by its low bioavailability owing to a significant gastric and hepatic first pass effect. This effect could be further diminished by likelihood of regurgitation of nauseating patients further limiting the therapeutic effect of oral PCZ. A buccal preparation achieves higher plasma concentrations through direct systemic absorption. In this study buccal prochlorperazine (Bukatel) was compared for its efficacy and tolerability with commonly used metoclopramide. Bukatel was well tolerated and well rated by both patients and investigators with no adverse effects on buccal mucosa and causing less drowsiness and sedation. Results indicate that Bukatel is safe and effective for the treatment of nausea and/or vomiting in patients suffering from vertiginous disorders and could be safely and strongly recommended as an alternative to less bioavailable and indiscriminately used oral metoclopramide tablets.

Pharmacokinetics and central nervous system toxicity of declopramide (3-chloroprocainamide) in rats and mice

Declopramide (3-chloroprocainamide) has been identified in previous studies as a representative of a new class of chemosensitizers. In this study, the toxicity and pharmacokinetics of declopramide have been investigated and compared with a structural analog, metoclopramide (MCA). Declopramide has not induced central nervous system (CNS)-related side effects in rats at doses up to 200 mg/kg, whereas MCA does at 12.5 mg/kg. In addition, declopramide did not bind to dopamine D2 receptors in subcellular preparations at doses up to 100 microM, whereas MCA showed affinity at 1 microM. Declopramide bound with affinity to 5-hydroxytryptamine3 receptors which are important in controlling vomiting. In contrast to MCA, declopramide has a rapid clearance from serum, a lower tissue concentration (about 15-fold lower than MCA) and a lower oral bioavailability (about 6-fold lower than MCA). However, declopramide was shown in vitro to possess a higher tumor cell absorption rate. One of the main metabolites of declopramide was identified as N-acetyl declopramide. Taken together, these data suggest that the clinical development of declopramide as a sensitizer of radio- and chemotherapies is an improvement over MCA, because it can be administered in a high dose and is devoid of CNS side effects.

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.

Neutral metoclopramide sensitizes cytotoxicity induced by ionizing radiation in SCID mice xenografted with a human brain astrocytoma

A formulation of metoclopramide (MCA) conformationally altered by neutralization of pH (nMCA, Neu-Sensamide) has been shown to have the same efficacy of enhancing the cytotoxicity of a single dose of 1 Gy radiation as acidic formulations (e.g., Primperan, Sensamide) in a human lung adenocarcinoma (H2981) xenografted into SCID mice. In the present study, 2 x 1 Gy radiation was combined with 2 x 2 mg nMCA/kg body weight injected 2 hr before radiation treatment for evaluation of radiosensitization in SCID mice xenografted with a human brain astrocytoma (T24). Given in this treatment schedule, nMCA alone at 2 mg/kg showed no cytotoxic effect on tumor growth in vivo. When combined with 2 x 1 Gy of radiation, however, the cytotoxicity was significantly increased as measured by tumor growth delay over the radiation-only-treated group. Furthermore, nMCA was absorbed into brains of mice and rats as efficiently as acidic MCA (aMCA) when analyzed 45 min after i.m. injection by high-performance liquid chromatography.

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.

Pharmacokinetics, toxicity, side effects, receptor affinities and in vitro radiosensitizing effects of the novel metoclopramide formulations, sensamide and neu-sensamide

Metoclopramide is a drug which has experienced worldwide use in the clinic for over 30 years as an antiemetic. Recently, it has also been shown to possess radio- and chemosensitizing properties in both animal tumour models and humans at the higher dose of 2 mg/kg. Two new metoclopramide formulations are being clinically developed and they differ mainly in whether the pH of their formulations are acidic (pH 2.5-3.5) or neutral (pH 6.5-7.0). Here we report that intramuscular administration of neutral metoclopramide is about 100% bioavailable, safer and with reduced side effects compared to acidic metoclopramide delivered by intramuscular injection to rats within the dose range of 3.5 to 14 mg/kg. The intramuscular administration of metoclopramide was also about 100% bioavailable compared to the intravenous route of administration. Furthermore, neutral metoclopramide had significantly decreased affinity for dopamine D2 receptors and increased affinity for 5-hydroxytryptamine, receptors, but the radiosensitizing potency was the same, when compared to equimolar concentrations of acidic metoclopramide. Taken together these data support the continued development of neutral metoclopramide for high dose intramuscular administration of metoclopramide for future clinical use as both an antiemetic and radiosensitizer.

Comparative central nervous system effects and pharmacokinetics of neu-metoclopramide and metoclopramide in healthy volunteers

Metoclopramide, a drug used for the relief of nausea and emesis, is currently under development as a radio- and chemosensitizing agent. Its usefulness in high doses, however, is limited by its central nervous system side effects. Neu-metoclopramide (Neu-Sensamide), a novel, concentrated, phosphate-buffered, pH-adjusted (pH = 6.5-7.0) formulation of metoclopramide, has been shown to have an improved side-effect profile in animal studies. The present double-blind, four-way crossover study compared the central nervous system effects and pharmacokinetics of neu-metoclopramide (intravenously and intramuscularly at 1.8 mg/kg) with intravenous metoclopramide and intramuscular placebo in 19 healthy male volunteers. Eight participants withdrew from the study, one because of noncompliance and seven because of adverse events. A total of 28 central nervous system events were observed with intravenous metoclopramide administration, whereas 16, 15, and 6 such events were attributed to intravenous neu-metoclopramide, intramuscular neu-metoclopramide, and placebo, respectively. Extra-pyramidal effects occurred on 10 occasions: 7 after intravenous metoclopramide, 2 after intravenous neu-metoclopramide, and 1 after intramuscular neu-metoclopramide. No significant differences were observed in the pharmacokinetic profiles of the three formulations of metoclopramide. It may be speculated, therefore, that the molecular conformational changes inherent to neu-metoclopramide result in a reduced side-effect profile compared with conventional metoclopramide formulations.

Pharmacokinetic optimisation in the treatment of gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GORD) is a very common disorder of upper gastro-intestinal motility, differing widely in severity and prognosis. Medical therapy of GORD has involved antacids, alginates, prokinetic agents and antisecretory compounds, primarily H2 receptor antagonists and proton pump inhibitors. Knowledge of the pharmacokinetics of these compounds is important, to optimise the therapeutic benefit in each patient. GORD patients are often elderly and pharmacokinetics are move variable in this group. Furthermore, they often suffer from other diseases needing medical therapy and may need a combination of drugs to heal reflux oesophagitis and relieve reflux symptoms. The ideal therapy for GORD will have linear pharmacokinetics, a relatively long plasma half-life (t1/2), a duration of action allowing once daily administration, and a stable effect independent of interactions with food, antacids and other drugs. Over-the-counter antacids and alginates are widely used, buy may affect absorption of H2 receptor antagonists like cimetidine and ranitidine. Aluminium-containing antacids may, over time, cause toxicity in patients with renal insufficiency. In the treatment of GORD, cisapride presents important advantages over earlier prokinetic compounds, with a longer plasma t1/2, low penetration of the blood-brain barrier and fewer adverse effects. The group of H2 receptor antagonists is still the most frequently use therapy for GORD. Linear pharmacokinetics make dose adjustments easy and safe. In individual patients, suppression of gastric secretion is related to the area under the plasma concentration-time curve (AUC), but there is wide interindividual variation in the effect of the same oral dose. Only with frequent administration and high doses will acid suppression approximate that of proton pump inhibitors. Tolerance, with loss of effect over time, however, is most pronounced in this situation. H2 receptor antagonists seem well suited for on-demand treatment of reflux symptoms, due to the rapid onset of effect and a decrease likelihood of the development of tolerance. Effervescent formulations provide more rapid absorption and almost immediate clinical effect. Cimetidine, however, causes interference with the metabolism of several other drugs in common use. In elderly patients elimination is delayed and in patients with renal insufficiency, dose reductions of all H2 receptor antagonists are recommended. The most effective medical therapy for any severity of GORD, particularly in severe oesophagitis, are the proton pump inhibitors. The substituted benzimidazoles (omeprazole, lansoprazole and pantoprazole), are prodrugs which once trapped and activated in the acid milieu of the gastric glands potently suppress gastric secretion of acid and pepsin. Their long duration of action, more related to the slow turnover of parietal cell H(+)-K+ ATPase molecules, allows once daily administration in most patients. Interindividual variation in bioavailability sometimes calls for higher doses or twice daily administration. Acid suppression is closely related to the AUC. Omeprazole is prone to interaction with the metabolism of other drugs, some of which may e be clinically important. Lansoprazole seems to have an earlier onset of action than omeprazole, ascribed to higher bioavailability during the first days of treatment. Proton pump inhibitors have a slow onset of action, which makes them unsuited for on-demand therapy. Clinical practice in GORD calls for the use of not one but several substances, according to the severity and symptom pattern of the patient. Pharmacokinetic optimisation in the treatment of GORD is a question of selecting the most suitable substances and administration schemes within each group. Cisapride is superior to other prokinetics in terms of longer plasma t1/2 and less toxicity. Amongst H2 receptor antagonists, the more long-acting compounds, ranitidine and famotidine, will improve acidity control througho

Indirect parasympathomimetic activity of metoclopramide: reversible inhibition of cholinesterases from human central nervous system and blood

Inhibitory effects of the dopamine D2-receptor antagonistic benzamide compound metoclopramide (MCP) on acetylcholinesterase (AChE; EC 3.1.1.7) isoenzymes of both erythrocytes and human caudate nucleus and on human serum cholinesterase (ChE; EC 3.1.1.8) were studied in vitro using a spectrophotometric assay with acetylthiocholine (ASCh) as substrate. MCP concentrations in the assays varied from 0.30 microM to 0.15 mM. All isoenzymes studied were inhibited by metoclopramide in a concentration-dependent manner. MCP inhibition of AChE and ChE isoenzymes was not time-dependent and of the reversible type. Double reciprocal plots of the reaction velocity against varying ASCh concentrations revealed that, for AChE isoenzymes of erythrocytes and of the caudate nucleus, MCP reduced both maximal reaction velocity (Vmax) and substrate affinity (apparent Michaelis constant, KM, increased). Thus, MCP inhibition of both AChE isoenzymes was of mixed competitive/non-competitive type. MCP constants for reversible competitive (Ki) and non-competitive (Ki) inhibition could be determined for erythrocyte AChE (Ki = 10 microM; Ki = 70 microM) and caudate nucleus AChE (Ki = 9.3 microM; Ki = 82 microM). In contrast to MCP inhibition of AChE isoenzymes, the type of reversible MCP inhibition of human serum ChE depended on substrate concentration. If substrate concentration exceeded 0.2 mM, MCP inhibition was of mixed competitive/non-competitive type (Ki = 0.19 microM; Ki = 1.4 microM). MCP inhibition was of uncompetitive type, if substrate concentration was below 0.2 mM (Ki(u) = 1.0 microM). The mixed-type MCP inhibition of cholinesterase isoenzymes, because of its non-competitive component, can only partially be overcome by increased concentrations of the cholinergic transmitter acetylcholine (ACh). Since, with intravenous infusions, peak MCP plasma concentrations in humans reach 4 microM, MCP inhibition of ACh hydrolysis in vivo may contribute both to prokinetic and anti-emetic actions of the substance and to its extrapyramidal side effects.

[The bioequivalence of metoclopramide in two tablet formulations]

An investigation on the bioavailability of a tablet with 10 mg metoclopramide-HCl (CAS 363-62-5) Cerucal was performed in a two-way cross-over study with 12 volunteers. Metoclopramide was determined in serum by HPLC. The relative bioavailability (mean and nonparametric 95% confidence interval) with respect to a reference preparation was 0.95 (95% CI 0.88-1.02) for AUC and 0.92 (95% CI 0.79-1.07) for Cmax. A positive decision for bioequivalence was derived from the usual confidence intervals for both parameters. The tmax-values did not differ significantly. Statistical evaluation of all parameters revealed bioequivalence between the two preparations.

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.

Comparison of the efficacy, safety, and pharmacokinetics of controlled release and immediate release metoclopramide for the management of chronic nausea in patients with advanced cancer

BACKGROUND

The short elimination half-life of metoclopramide necessitates frequent administration for optimal relief of nausea. This study compares a newly developed controlled release preparation of metoclopramide (CRM) and immediate release metoclopramide (IRM) with respect to efficacy, safety, and pharmacokinetics in patients with chronic nausea associated with advanced cancer.

METHODS

Thirty-four patients with advanced cancer with nausea lasting more than 1 month and with no evidence of involvement of the gastrointestinal tract, peptic ulcer or gastritis, brain metastases, or metabolic abnormalities were randomized, in a double-blind cross-over study, to receive 40 mg of CRM every 12 hours or 20 mg of IRM every 6 hours for 3 days. Nausea, food intake, and side effects were assessed four times daily. On Day 3, sequential venous samples were taken (12 patients) to determine plasma metoclopramide concentrations.

RESULTS

In 29 evaluable patients, the intensity of nausea on Day 3, measured by a 0-100-mm visual analogue scale and 0-3 categoric scale was 15 +/- 17 and 0.6 +/- 0.6 after IRM, versus 8 +/- 9 (P = 0.033) and 0.4 +/- 0.5 (P = 0.055) after CRM, respectively. Visual analogue scale nausea scores recorded by time of day and by day for the 3 treatment days were significantly lower for patients who received CRM compared with those who received IRM (P = 0.047 and P = 0.043, respectively), but categoric nausea scores were not significantly different between treatments by time of day and by day across the 3 treatment days. No differences were observed in caloric intake or side effects between treatments. In a pharmacokinetic analysis, the CRM/IRM ratio for area under the curve0-12 (microgram x hours x L-1), Cmax (microgram/L), and Tmax (hours) was 100%, 98%, and 2.3 fold, respectively.

CONCLUSION

Controlled release metoclopramide is safe and effective in managing chronic nausea in patients with advanced cancer. Future studies should focus on characterizing this syndrome more clearly and on determining the optimal dose of metoclopramide and the effects of drug combinations that have proven to be useful in managing chemotherapy-induced emesis (i.e., metoclopramide plus corticosteroids).