The pharmacokinetics of high dose metoclopramide in patients with neoplastic disease

A systematic review of the treatment of nausea and/or vomiting in cancer unrelated to chemotherapy or radiation

CONTEXT

A systematic review of antiemetics for emesis in cancer unrelated to chemotherapy and radiation is an important step in establishing treatment recommendations and guiding future research. Therefore, a systematic review based on the question "What is the evidence that supports antiemetic choices in advanced cancer?" guided this review.

OBJECTIVES

To determine the level of evidence for antiemtrics in the management of nausea and vomiting in advanced cancer unrelated to chemotherapy and radiation, and to discover gaps in the evidence, which would provide important areas for future research.

METHODS

Three databases and independent searches using different MeSH terms were performed. Related links were searched and hand searches of related articles were made. Eligible studies included randomized controlled trials (RCTs), prospective single-drug studies, studies that used guidelines based on the etiology of emesis, cohort studies, retrospective studies, and case series or single-patient reports. Studies that involved treatment of chemotherapy, radiation, or postoperation-related emesis were excluded. Studies that involved the treatment of emesis related to bowel obstruction were included. The strength of evidence was graded as follows: 1) RCTs, A; 2) single-drug prospective studies, B1; 3) studies based on multiple drug choices for etiology of emesis, B2; and 4) cohort, case series, retrospective, and single-patient reports, E. Level of evidence was determined by the Oxford Centre for Evidence-Based Medicine Levels of Evidence (May 2001) (A, B, C, D).

RESULTS

Ninety-three articles were found. Fourteen were RCTs, most of them of low quality, based either on lack of blinding, lack of description of the method of randomization, concealment, and/or attrition. Metoclopramide had modest evidence (B) based on RCTs and prospective cohort studies. Octreotide, dexamethasone, and hyoscine butylbromide are effective in reducing symptoms of bowel obstruction, based on prospective studies and/or one RCT. There was no evidence that either multiple antiemetics or antiemetic choices based on the etiology of emesis were any better than a single antiemetic. There is poor evidence for dose response, intraclass or interclass drug switch, or antiemetic combinations in those individuals failing to respond to the initial antiemetic.

CONCLUSION

There are discrepancies between antiemetic studies and published antiemetic guidelines, which are largely based on expert opinion. Antiemetic recommendations have moderate to weak evidence at best. Prospective randomized trials of single antiemetics are needed to properly establish evidence-based guidelines.

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.

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.

Linearity of metoclopramide kinetics at doses of 5-20 mg

The disposition of metoclopramide was studied on a four-way crossover basis in six healthy non-smoking volunteers. The linearity of kinetic parameters and absolute bioavailability of metoclopramide were examined. In contrast to previous reports, metoclopramide obeyed linear kinetics over oral doses ranging from 5 to 20 mg. The absolute bioavailability of metoclopramide was 0.76 +/- 0.38 (mean +/- s.d.) from the oral dosage forms examined in this study.

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%.

Bioavailability and disposition of metoclopramide after single- and multiple-dose administration in diabetic patients with gastroparesis

The disposition of metoclopramide after acute and chronic administration was determined in four diabetic patients with gastroparesis who had a creatinine clearance of 70.8 +/- 10.7 mL/min (mean +/- SD). Single, 10-mg oral and intravenous doses were administered on days 1 and 2, respectively, followed by 10 mg orally every six hours for three weeks. A second, 10-mg intravenous bolus dose was administered on the last morning of chronic therapy. Metoclopramide concentrations were determined by high performance liquid chromatography. The elimination half-life, steady-state volume of distribution, and total body clearance after the initial intravenous dose were 3.9 +/- 1.2 hr, 2.7 +/- 0.3 L/kg, and 0.57 +/- 0.14 L/hr/kg, respectively. The initial bioavailability was 67.7 +/- 12.6%. After three weeks of chronic therapy, no significant differences in total body clearance (0.72 +/- 0.42 L/hr/kg) or bioavailability (77.5 +/- 16.8%) were observed. Thus the pharmacokinetics and bioavailability of metoclopramide were not altered during chronic therapy in these diabetic patients.

High-dose metoclopramide by infusion: a double-blind study of plasma concentration-effect relationships in patients receiving cancer chemotherapy

We have carried out a randomized, double-blind trial to investigate the relationship between the dose and plasma concentration of metoclopramide and its anti-emetic efficacy and adverse effects in patients receiving cancer chemotherapy. Seventeen patients received four different infusion regimens of high-dose metoclopramide in random order with four consecutive courses of chemotherapy, to achieve an approximately eight-fold range in plasma metoclopramide concentrations. In patients receiving cisplatin the incidence of vomiting decreased with increasing metoclopramide dose, but the overall efficacy was poor. There was no relationship between anti-emetic efficacy and either dose or plasma concentration of metoclopramide in patients receiving cyclophosphamide and doxorubicin. The adverse effects of high-dose metoclopramide included diarrhoea, which increased in incidence with increasing metoclopramide dose, and sedation and extrapyramidal reactions, which were not related to dose or plasma concentration. Although anti-emetic efficacy increases with increasing metoclopramide dose in patients receiving cisplatin, high-dose metoclopramide alone does not adequately control cisplatin-induced nausea and vomiting.

Pharmacokinetics of high-dose metoclopramide in cancer patients

The introduction of new cytotoxic drug regimens has been associated with an increase in the incidence and severity of adverse effects. This in turn has highlighted the need for more effective adjuvant therapy. The use of metoclopramide for the prophylaxis of nausea and vomiting, in high intravenous doses (50 to 1000 mg), has become established since 1981. As a lipid-soluble drug, metoclopramide has a large volume of distribution. The reported mean values after high doses range between 2.8 and 4.6 L/kg. The mean values for total body clearance and terminal half-life range from 0.31 to 0.69 L/kg/h and from 4.5 to 8.8 hours, respectively. The values of these pharmacokinetic parameters are essentially similar to those obtained after conventional doses (less than 50mg). Pharmacokinetic parameters appear unaffected by age, although no high-dose study has been conducted in children. Bodyweight is apparently correlated with clearance. An influence of renal function indices on terminal half-life and clearance has been shown, which is rather surprising since renal clearance accounts for only 20% of the total clearance. No thorough investigations exist which examine the influence of hepatic disease, cancer type and cytotoxic drug regimen on the disposition of metoclopramide. A relationship between dose (or concentration) and therapeutic or adverse effects of metoclopramide is outlined. The therapeutic benefit of high doses (up to 14 mg/kg) may be dependent on age, and on the combination of cytotoxic drugs. The advantages of high doses of metoclopramide are most apparent when the drug is used as protection against the adverse effects of high doses of cisplatin (greater than 60 mg/m2). Despite considerable pharmacokinetic variability, intravenous administration of high doses of metoclopramide is relatively safe due to its large therapeutic index.