In general, the incidence of adverse reactions correlates with the dose and duration of metoclopramide administration. The following reactions have been reported, although in most instances, data do not permit an estimate of frequency.
CNS Effects: Restlessness, drowsiness, fatigue, and lassitude occur in approximately 10% of patients receiving the most commonly prescribed dosage of 10 mg q.i.d. (see PRECAUTIONS). Insomnia, headache, confusion, dizziness, or mental depression with suicidal ideation (see WARNINGS) occur less frequently. There are isolated reports of convulsive seizures without clearcut relationships to metoclopramide. Rarely, hallucinations have been reported.
Extrapyramidal Reactions (EPS): Acute dystonic reactions, the most common type of EPS associated with metoclopramide, occur in approximately 0.2% of patients (1 in 500) treated with 30 to 40 mg of metoclopramide per day. Symptoms include involuntary movements of limbs, facial grimacing, torticollis, oculogyric crisis, rhythmic protrusion of tongue, bulbar type of speech, trismus, opisthotonus (tetanus-like reactions), and rarely, stridor and dyspnea possibly due to laryngospasm; ordinarily these symptoms are readily reversed by diphenhydramine (see WARNINGS).
Parkinsonian-like symptoms may include bradykinesia, tremor, cogwheel rigidity, masklike facies (see WARNINGS).
Tardive dyskinesia most frequently is characterized by involuntary movements of the tongue, face, mouth, or jaw, and sometimes by involuntary movements of the trunk and/or extremities; movements may be choreoathetotic in appearance (see WARNINGS).
Motor restlessness (akathisia) may consist of feelings of anxiety, agitation, jitteriness, and insomnia, as well as inability to sit still, pacing, foot-tapping. These symptoms may disappear spontaneously or respond to a reduction in dosage.
Endocrine Disturbances: Galactorrhea, amenorrhea, gynecomastia, impotence secondary to hyperprolactinemia (see PRECAUTIONS). Fluid retention secondary to transient elevation of aldosterone (see CLINICAL PHARMACOLOGY).
Cardiovascular: Hypotension, hypertension, supraventricular tachycardia, bradycardia, fluid retention, acute congestive heart failure and possible AV block (see CONTRAINDICATIONS and PRECAUTIONS).
Gastrointestinal: Nausea and bowel disturbances, primarily diarrhea.
Hepatic: Rarely, cases of hepatotoxicity, characterized by such findings as jaundice and altered liver function tests, when metoclopramide was administered with other drugs with known hepatotoxic potential.
Renal: Urinary frequency and incontinence.
Hematologic: A few cases of neutropenia, leukopenia, or agranulocytosis, generally without clearcut relationships to metoclopramide. Methemoglobinemia, especially with overdosage in neonates (see OVERDOSAGE).
Sulfhemoglobinemia in adults.
Allergic Reactions: A few cases of rash, urticaria, or bronchospasm, especially in patients with a history of asthma. Rarely, angioneurotic edema, including glossal or laryngeal edema.
Miscellaneous: Visual disturbances. Porphyria. Rare occurrences of neuroleptic malignant syndrome (NMS) have been reported. This potentially fatal syndrome is comprised of the symptom complex of hyperthermia, altered consciousness, muscular rigidity, and autonomic dysfunction.
Transient flushing of the face and upper body, without alterations in vital signs, following high doses intravenously.