General
In one study in hypertensive patients, intravenously
administered metoclopramide was shown to release catecholamines; hence, caution
should be exercised when metoclopramide is used in patients with
hypertension.
Because metoclopramide produces a transient increase in plasma aldosterone,
certain patients, especially those with cirrhosis or congestive heart failure,
may be at risk of developing fluid retention and volume overload. If these side
effects occur at any time during metoclopramide therapy, the drug should be
discontinued.
Adverse reactions, especially those involving the nervous system, may occur
after stopping the use of metoclopramide tablets. A small number of patients may
experience a withdrawal period after stopping metoclopramide tablets that could
include dizziness, nervousness and/or headaches.
Information for Patients
The use of metoclopramide tablets is recommended for adults
only. Metoclopramide may impair the mental and/or physical abilities required
for the performance of hazardous tasks such as operating machinery or driving a
motor vehicle. The ambulatory patient should be cautioned accordingly.
For additional information, patients should be instructed to see the
Medication Guide for Metoclopramide tablets.
Drug Interactions
The effects of metoclopramide on gastrointestinal motility
are antagonized by anticholinergic drugs and narcotic analgesics. Additive
sedative effects can occur when metoclopramide is given with alcohol, sedatives,
hypnotics, narcotics, or tranquilizers.
The finding that metoclopramide releases catecholamines in patients with
essential hypertension suggests that it should be used cautiously, if at all, in
patients receiving monoamine oxidase inhibitors.
Absorption of drugs from the stomach may be diminished (e.g., digoxin) by
metoclopramide, whereas the rate and/or extent of absorption of drugs from the
small bowel may be increased (e.g., acetaminophen, tetracycline, levodopa,
ethanol, cyclosporine).
Gastroparesis (gastric stasis) may be responsible for poor diabetic control
in some patients. Exogenously administered insulin may begin to act before food
has left the stomach and lead to hypoglycemia. Because the action of
metoclopramide will influence the delivery of food to the intestines and thus
the rate of absorption, insulin dosage or timing of dosage may require
adjustment.
Carcinogenesis, Mutagenesis, Impairment of Fertility
A 77-week study was conducted in rats with oral doses up to
about 40 times the maximum recommended human daily dose. Metoclopramide elevates
prolactin levels and the elevation persists during chronic administration.
Tissue culture experiments indicate that approximately one-third of human breast
cancers are prolactin-dependent in vitro, a factor of
potential importance if the prescription of metoclopramide is contemplated in a
patient with previously detected breast cancer. Although disturbances such as
galactorrhea, amenorrhea, gynecomastia, and impotence have been reported with
prolactin-elevating drugs, the clinical significance of elevated serum prolactin
levels is unknown for most patients. An increase in mammary neoplasms has been
found in rodents after chronic administration of prolactin-stimulating
neuroleptic drugs and metoclopramide. Neither clinical studies nor epidemiologic
studies conducted to date, however, have shown an association between chronic
administration of these drugs and mammary tumorigenesis; the available evidence
is too limited to be conclusive at this time.
An Ames mutagenicity test performed on metoclopramide was negative.
Pregnancy Category B
Reproduction studies performed in rats, mice and rabbits by
the I.V., I.M., S.C., and oral routes at maximum levels ranging from 12 to 250
times the human dose have demonstrated no impairment of fertility or significant
harm to the fetus due to metoclopramide. There are, however, no adequate and
well-controlled studies in pregnant women. Because animal reproduction studies
are not always predictive of human response, this drug should be used during
pregnancy only if clearly needed.
Nursing Mothers
Metoclopramide is excreted in human milk. Caution should be
exercised when metoclopramide is administered to a nursing mother.
Pediatric Use
Safety and effectiveness in pediatric patients have not
been established (see OVERDOSAGE).
Care should be exercised in administering metoclopramide to neonates since
prolonged clearance may produce excessive serum concentrations (see CLINICAL PHARMACOLOGY—Pharmacokinetics).
In addition, neonates have reduced levels of NADH-cytochrome b5 reductase which, in combination with the aforementioned
pharmacokinetic factors, make neonates more susceptible to methemoglobinemia
(see OVERDOSAGE).
The safety profile of metoclopramide in adults cannot be extrapolated to
pediatric patients. Dystonias and other extrapyramidal reactions associated with
metoclopramide are more common in the pediatric population than in adults. (See
WARNINGS and ADVERSE REACTIONS—Extrapyramidal Reactions.)
Geriatric Use
Clinical studies of metoclopramide tablets did not include
sufficient numbers of subjects aged 65 and over to determine whether elderly
subjects respond differently from younger subjects.
The risk of developing parkinsonian–like side effects increases with
ascending dose. Geriatric patients should receive the lowest dose of
metoclopramide tablets that is effective. If parkinsonian like symptoms develop
in a geriatric patient receiving metoclopramide tablets, metoclopramide tablets,
should generally be discontinued before initiating any specific
anti-parkinsonian agents(see WARNINGS
and DOSAGE AND ADMINISTRATION – For the
Relief of Symptomatic Gastroesophageal Reflux).
The elderly may be at greater risk for tardive dyskinesia (see WARNINGS –Tardive Dyskinesia).
Sedation has been reported in metoclopramide tablets users. Sedation may
cause confusion and manifest as over-sedation in the elderly (see CLINICAL PHARMACOLOGY, PRECAUTIONS-Information for Patientsand ADVERSE REACTIONS – CNS Effects).
Metoclopramide tablets is known to be substantially excreted by the kidney
and the risk of toxic reactions to this drug may be greater in patients with
impaired renal function (see DOSAGE AND
ADMINISTRATION - Use in Patients with Renal or Hepatic Impairment).
For these reasons, dose selection for an elderly patient should be cautious,
usually starting at the low end of the dosing range, reflecting the greater
frequency of decreased renal function, concomitant disease, or other drug
therapy in the elderly (see DOSAGE AND
ADMINISTRATION – For the Relief of Symptomatic Gastroesophageal Reflux
and Use in Patients with Renal or
Hepatic Impairment).
Other Special Populations
Patients with NADH-cytochrome b5
reductase deficiency are at an increased risk of developing methemoglobinemia
and/or sulfhemoglobinemia when metolcopramide is administered. In patients with
G6PD deficiency who experience metoclopramide-induced methemoglobinemia,
methylene blue treated is not recommended (see OVERDOSAGE).