Pharmacokinetics of high-dose metoclopramide in cancer patients

Unveiling the Unprecedented: An Astonishing Rarity of Metoclopramide Hydrochloride-Triggered Nystagmus in a Pregnant Woman

Metoclopramide hydrochloride is a widely used medication for the treatment of gastrointestinal disorders such as nausea, vomiting, and gastroparesis. However, it has been associated with extrapyramidal side effects (EPS) such as tardive dyskinesia, nystagmus, and other locomotive disorders on rare occasions. These reactions are commonly seen in children and females, particularly in young people. In this article, we report a rare case of a 15-week pregnant woman who was prescribed metoclopramide hydrochloride in view of nausea and vomiting, which was later diagnosed as vomiting in pregnancy not relieved with first-line medications, and has later developed drug-induced nystagmus, highlighting its unpredictable nature and shortcomings of management in the pregnant woman. This article will draw the attention of obstetricians and gynecologists to wisely prescribe metoclopramide hydrochloride for treating nausea and vomiting in pregnant women.

Self-assumed Neurologic Related Condition Deviated Metoclopramide-Induced Acute Dystonic of Oculogyric Crisis in a Woman of Childbearing Age: A Case Report

A 26-year-old Malaysian woman (childbearing age) attended a private primary care clinic with a known case of gastroesophageal reflux disease (GERD) and complained of persistent nausea and a few episodes of vomiting. She had no known drug allergy, no surgical history, no hospitalization in the last two years, was a non-smoker, and no history of drug or alcohol abuse. The patient was prescribed Tab metoclopramide 10 mg TDS and Tab ranitidine 150 mg BD for five days. About 30 min after oral administration of both medicines, her eyes rolled involuntary upward, leading to lateral deviation of the eyes, and mouth jaws clenched as if “dislocated jaws.” The patient was immediately brought into an emergency department (ED) of a public tertiary care hospital. A drug challenge test was done which resulted in the withdrawal of metoclopramide. The accompanied sister later disclosed that the patient had taken metoclopramide and ranitidine from a private clinic earlier in the day. The patient self-assumed to have a sudden seizure, due to excessive hot weather and dehydration. A slow intravenous infusion of 50 mg/mL diphenhydramine hydrochloride in 0.9% w/v NaCl 100 mL was administered stat. Consequently, the symptoms vanished after approximately 30 min of the therapy, devoid of relapse. The patient was discharged from ED post 8 hours of monitoring with complete recovery. Physicians frequently prescribe metoclopramide to treat nausea and vomiting, which may cause adverse drug reaction of acute dystonic oculogyric crisis (OGC). Due to its unwanted and unpredictable extrapyramidal symptoms, metoclopramide should be prescribed and dispensed with caution. Thorough history taking at ED is imperative for correct early diagnosis and treatment, as metoclopramide-induced dystonic OGC has a high probability of confusion with other causes of dystonia such as conversion and seizures, encephalitis, tetanus, and hypercalcemic tetany.

Postmortem Drug Redistribution: A Compilation of Postmortem/Antemortem Drug Concentration Ratios

Postmortem drug redistribution (PMR) is a well-known phenomenon in forensic toxicology with implications for medico-legal death investigations. Paired antemortem (AM) specimen and postmortem (PM) mortuary admission femoral blood drug concentrations from 811 coronial cases were used to construct a retrospective compilation of PM/AM drug concentration ratios for 42 parent drugs and metabolites. The median PM/AM ratios for all antidepressants were > 1 and consistent with PMR In contrast, the median PM/AM ratios of most benzodiazepines were < 1. The antipsychotics were varied (0.63-3.3) and suggest the mixed effects of PMR and drug instability. Amphetamines exhibited no trends (0.90-0.95) and are likely confounded by many factors. The PM/AM ratios of cardiovascular drugs, opioids and other drugs are also reported. This research represents an expansive retrospective compilation of paired AM and PM drug concentrations for many toxicologically relevant drugs. While the median PM/AM ratios demonstrate some drug-dependent trends, there was no obvious relationship between AM specimens and PM femoral blood taken at mortuary admission.

Interactions between metoclopramide and morphine: enhanced antinociception and motor dysfunction in rats

1. Opioid analgesics and anti-emetics are often used concomitantly to treat pain and nausea and vomiting in people with malignant disease. We investigated interactions between the opioid analgesic morphine and the anti-emetic metoclopramide, a dopamine D2 receptor antagonist, on nociception and gross motor function. 2. To assess for antinociceptive interactions, 11 Sprague-Dawley rats were injected intraperitoneally with morphine (5.0 mg/kg) or saline in combination with metoclopramide (0.5, 1.5 and 5.0 mg/kg) or saline and, 30 min later, the tail-flick latencies to a noxious thermal stimulus (49 degrees C water) were measured. Immediately thereafter we induced reperfusion hyperalgesia in the rats' tails using a tourniquet cuff and tested nociception again. Because, in addition to its ability to block D2 receptors, metoclopramide is also a weak 5-HT(3) receptor antagonist, we assessed in a further 11 rats whether any antinociceptive interactions occurred between morphine (5.0 mg/kg) and ondansetron (0.2 and 2.0 mg/kg), an anti-emetic that selectively antagonizes 5-HT(3) receptors. To assess for motor interactions, we injected another group of nine rats with morphine (5.0 mg/kg) or saline in combination with metoclopramide (0.5 and 5.0 mg/kg) or saline and tested the ability of the animals to run on an 80 mm diameter rod rotating at 25 r.p.m. for 30 min. 3. Metoclopramide was not inherently analgesic or antihyperalgesic, but the highest dose of metoclopramide (5.0 mg/kg) enhanced the analgesic and antihyperalgesic effects of morphine. Neither dose of ondansetron was analgesic or antihyperalgesic or enhanced the antinociceptive actions of morphine. 4. Only the high dose of metoclopramide compromised running performance when administered with saline. However, coadministering morphine with metoclopramide (both doses) decreased motor performance. 5. Therefore, metoclopramide, possibly through its actions on D2 receptors and not 5-HT(3) receptors, enhances the analgesic and antihyperalgesic effects of morphine, but morphine exacerbates metoclopramide-induced motor dysfunction in rats.

In vitro protection of plasma cholinesterases by metoclopramide from inhibition by paraoxon

Metoclopramide (MCP) is a dopamine receptor antagonist and serotonine receptor agonist widely used as an antiemetic and gastric prokinetic drug. In addition MCP is a reversible inhibitor of cholinesterases from human central nervous system and blood. MCP may have a cholinesterase protective effect against inhibition by organophosphates. The purpose of the study was to quantify "in vitro" by means of the IC(50)-shift the extent of MCP conferred protection, using paraoxon (POX) as an inhibitor. POX is a widely used organophospate responsible for a large number of accidental or suicidal exposures. Cholinesteratic activities (ChE) (with acetyl-thiocholine (A) and butyryl-thiocholine (B) as substrates) in human plasma were measured photometrically in the presence of different POX concentrations and IC(50) was calculated. Determinations were repeated in the presence of increasing MCP concentrations. It appears that the shift induced by the presence of MCP increases with the MCP concentration in a linear manner. In the presence of a clinically easily achievable plasma concentration of 1 micro M MCP the IC(50) of POX for ChE 'shifts' by a factor of approximately 2-3. The protective effect of metoclopramide on cholinesterases could be of practical relevance in the treatment of paraoxon poisoning. We conclude that in vivo testing of MCP as an organophosphate protective agent is warranted.

In vitro protection of red blood cell acetylcholinesterase by metoclopramide from inhibition by organophosphates (paraoxon and mipafox)

Metoclopramide (MCP) is a dopamine receptor antagonist and serotonin receptor agonist widely used as an antiemetic and gastric prokinetic drug. In addition, MCP is a reversible inhibitor of cholinesterases from the human central nervous system and blood, and may have a red blood cell (RBC) acetylcholinesterase (AChE) protective effect against inhibition by organophosphates. The purpose of the study was to quantify 'in vitro', by means of the IC50 shift, the extent of MCP conferred protection, by using paraoxon (POX) and mipafox (MPFX) as inhibitors. Paraoxon is a widely used non-neuropathic organophospate responsible for a large number of accidental or suicidal exposures. Mipafox is a neuropathic organophospate. Red blood cell AChE activities in human plasma were measured photometrically in the presence of different POX, MPFX and MCP concentrations and the IC50 was calculated. Determinations were repeated in the presence of increasing MCP concentrations. It appears that the IC50 shift induced by the presence of MCP increases with the MCP concentration in a linear manner. The protective effect of MCP on cholinesterases could be of practical relevance in the treatment of POX and MPFX poisoning. We conclude that in vivo testing of MCP as an organophosphate protective agent is warranted.

Analgesic action of metoclopramide in prosthetic hip surgery

Prosthetic hip surgery was performed under subarachnoidal anaesthesia with bupivacaine 16-20 mg and morphine 0.2 mg. Preoperatively, metoclopramide 1 mg.kg-1 was given i.v., followed by an infusion of 1.5 mg.kg-1 over 9 h (n = 17). Control patients received corresponding volumes of solvent (n = 23. The design of the study was double blind. The characteristics of the spinal block (level of analgesia to pinprick and muscular block) and postoperative VAS pain scores were similar in both groups. During the 24 h following the start of the infusion, four patients receiving metoclopramide required i.v. opioids, compared to 15 in the control group (P < 0.05). The pain-free period was longer (P < 0.05) in the metoclopramide group. Arterial PCO2-levels were increased, reaching a maximum within 6 h of infusion, with no significant difference between the groups. The study suggests an analgesic action of metoclopramide.

Controlling cancer chemotherapy-induced emesis. An update

Cytotoxic chemotherapy can induce acute, delayed and anticipatory nausea and vomiting. The efficacy and toxicity data of the available anti-emetics and their role in chemotherapy-induced emesis are reviewed. Moreover, some pitfalls in the methodology of anti-emetic trials as well as factors known to affect the individual sensitivity of patients for the emetic challenge are illustrated. So far, high-dose metoclopramide (3-6 mg.kg-1.d-1) was the most effective single agent in the control of acute emesis. However, extrapyramidal reactions caused by its dopamine antagonism remained a major drawback. The addition of dexamethasone and/or lorazepam decreases the incidence of extrapyramidal reactions, and further improves anti-emetic control. In animals, serotonin type 3 receptor antagonists have demonstrated promising anti-emetic results against chemotherapy-induced and radiotherapy-induced emesis; the results of clinical studies are awaited. Delayed nausea and vomiting have not been studied as extensively. At present, the combination of metoclopramide and dexamethasone offers an optimal protection in approximately 50% of patients on cisplatin chemotherapy. Anticipatory nausea and emesis remain major problems, and an effective pharmacological treatment is lacking. Attempts to control this type of emesis focus on drugs with amnesic properties and on behaviour therapy.

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.

Continuous infusion of high-dose metoclopramide: comparison of pharmacokinetically adjusted and standard doses for the control of cisplatin-induced acute emesis

Metoclopramide was administered by continuous infusion to two groups each of 14 patients on chemotherapy, randomized to receive either doses adjusted to individual pharmacokinetic parameters or doses adjusted as usual to body weight. The mean plasma concentration at the end of the infusion in the adjusted group was 1.01 mg.l-1, close to that aimed for (1.20 mg.l-1). It was significantly different from that in the other group. v 0.54 mg.l-1. Antiemetic efficacy, defined as less than or equal to 2 emetic events in the 24 h following cisplatin, was similar in both groups (being found in 12/14 (86%) and 10/14 patients (71%), respectively). Analysis of the cumulative percentage of responders according to plasma concentration showed a clear plasma concentration-effect relationship. Routine MCP pharmacokinetic dosage adjustment is not indicated, but this therapeutic approach can be used to optimize antiemetic therapy in poor responder patients.

Pharmacokinetics of metoclopramide in patients with liver cirrhosis

The pharmacokinetics of metoclopramide were investigated after intravenous and oral administration in eight patients with severe alcoholic cirrhosis and in eight healthy volunteers. As a consequence of a 50% lower clearance (0.16 +/- 0.07 vs 0.34 +/- 0.09 l h-1 kg-1, plasma drug concentrations and the half-life of metoclopramide were greater in patients following both routes of drug administration. Volume of distribution (3.1 +/- 0.8 vs 3.4 +/- 1.2 l kg-1) and absolute bioavailability (79 +/- 19 vs 84 +/- 15%) were similar in the two groups. The adverse effects of metoclopramide observed in patients with marked hepatic impairment are likely to result from increased accumulation of the drug as a result of impaired clearance. Consequently a reduction in dose of 50% is recommended in patients with severe liver cirrhosis.

Population analysis of the pharmacokinetic variability of high-dose metoclopramide in cancer patients

Metoclopramide infusions are used to prevent nausea and vomiting in cancer patients during chemotherapy. 47 patients received metoclopramide during 109 chemotherapeutic treatments as a loading (dose range = 0.55 to 4.5 mg/kg over 15 minutes) and maintenance (dose range = 0.57 to 4.8 mg/kg over 8 hours) infusion. During and up to 24 hours after the end of the maintenance infusion between 4 and 10 blood samples were collected per treatment. Metoclopramide was analysed in plasma by liquid chromatography. Pharmacokinetic and demographic data of 83 treatments were analysed by the NONMEM program using a linear 2-compartment model. It was found that bodyweight and serum alkaline phosphatase activity explain some of the interindividual variability in clearance (CL). The typical pharmacokinetic parameters for an average individual (70kg, alkaline phosphatase = 100 IU/L) were: CL = 20 L/h; volume of distribution at steady state (Vdss) = 190L; terminal half-life = 8h. The interindividual variabilities in clearance, volume of central compartment and Vdss were 50%, 35% and 35%, respectively. The residual variability in plasma concentrations was estimated as 13%.