Incomplete absorption of glucose-galactose (Lapp lactase deficiency or galactose intolerance)
As Ondansetron contains lactose and therefore patients with galactose intolerance should not take this medicine.
Patients with liver problems should consult with the doctor. Also, for children who are on Ondansetron treatment in combination with chemotherapeutic agents having damaging effects on the liver should be monitored closely for any damage to the liver.
Masking of bleeding
Patients who have undergone the surgical procedure for removal of adenoids (patch of tissues behind the nose), for the prevention
and vomiting with Ondansetron are at an increased risk of masking of bleeding
. Such patients should be carefully monitored after giving Ondansetron.
Time taken for food to travel through the digestive tract (bowel transit time)
Patients with signs of subacute prevention
of passage of digested food through the bowel (intestinal obstruction) should be monitored following dosage, as Ondansetron increases the large bowel transit time.
Genetic birth defect causing the build-up of an amino acid in the body (phenylketonuria)
Patients with phenylketonuria
should be informed that Ondansetron orally disintegrating tablets contain phenylalanine, which is a component of sweetener.
Masking of progressive bloating of the stomach (ileus and gastric distension)
Patients using Ondansetron after the stomach surgery
or in patients with chemotherapy-induced nausea
and vomiting may mask a progressive ileus
and gastric distension. Monitoring of decreased bowel activity, particularly in patients who are at an increased risk for stomach and intestinal blockage is recommended. Ondansetron should not be used to activate a series of muscle contractions in the digestive tract (gastric or intestinal peristalsis).
Life-threatening syndrome induced by use of serotonergic drugs (serotonin syndrome)
Patients who are on treatment with certain medicines (histamine receptor antagonists, serotonin reuptake inhibitors, serotonin, and norepinephrine reuptake inhibitors) are at an increased risk to develop serotonin syndrome
which can be fatal in some cases. The syndrome has also occurred in patients after inducing a temporary loss of sensation (anesthesia
) or in an infusion center. These patients may develop symptoms such as agitation, hallucinations
, increased heartbeat, sudden rise in blood pressure, dizziness
, sweating (diaphoresis), flushing, increased body temperature, tremor
, rigidity, sudden muscle contraction
), overactive reflexes (hyperreflexia), incoordination, seizures
, vomiting, or diarrhea
. Such patients should be carefully monitored for the development of serotonin syndrome, occurring most commonly with the use of Ondansetron and other serotonergic drugs together. If any symptom of serotonin syndrome appears, the use of Ondansetron should be discontinued, and supportive treatment should be started.
Abnormal heartbeat (QT prolongation)
Patients consuming Ondansetron are at increased risk of developing abnormal heartbeat (QT prolongation). Avoid the use of Ondansetron in patients with abnormal heartbeat (congenital QT prolongation). An ECG monitoring is recommended in patients with congestive heart failure, slow heartbeat, electrolyte abnormalities, and abnormal heart rhythms.
Severe allergic reactions
Patients who are allergic to Ondansetron are at an increased risk when using this medicine. Such patients may have an increased risk of developing allergic reactions such as life-threatening allergic reaction (anaphylaxis
) and tightening of the muscles of the lungs (bronchospasm). If such allergic reactions occur, the use of Ondansetron should be discontinued, and the patient should be monitored carefully until the signs and symptoms go away.