Ondansetron - instructions for use, dose, side effects, contraindications

Antiemetic drug, most effective for preventing vomiting during chemotherapy of tumors. Antineoplastic cytotoxic agents act primarily on rapidly dividing cells, in particular on the epithelium of the gastrointestinal tract. With the action of cytotoxic substances on the epithelium of the stomach and intestines is released serotonin, which activates serotonin 5-HT₃- receptors on the ends of the afferent nerve fibers and causes vomiting. The drug selectively blocks serotonin 5-HT₃- receptors both in the central (bottom IV ventricle), and in the peripheral nervous system (the end of the vagus in the intestine), which are responsible for the implementation of the emetic reflex.

Pharmacokinetics:

Bioavailability of the drug is 56%. The connection with plasma proteins is 70-76%. Metabolized in the liver with the participation of isoenzymes of the cytochrome system. The half-life is 5.7 hours in adults and 2.5-3 hours in children. Excreted by the gastrointestinal tract, to a lesser extent by the kidneys (5%).

Indications:

Prevention of vomiting and nausea in the postoperative period.

Prevention of vomiting and nausea when carrying out anti-tumor chemotherapy or radiation therapy.

ICD-10

XVIII.R10-R19.R11 Nausea and vomiting

XX.Y83-Y84.Y84.2 Radiological procedure and radiation therapy

XXI.Z40-Z54.Z51.0 Radiotherapy course (supportive)

XXI.Z40-Z54.Z51.1 Chemotherapy for neoplasm

XXI.Z80-Z99.Z98.8 Other specified post-surgical conditions

Contraindications:

- hypersensitivity to ondansetron;

- Pregnancy I trimester;

- breast-feeding;

- combined use with apomorphine;

- congenital lengthening syndrome QT;

- Children under 6 months of age by indication of nausea and vomiting in chemotherapy or radiotherapy;

- children's age up to 1 month according to nausea and vomiting in the postoperative period.

Carefully:

Surgical interventions on the abdominal cavity. Children's age (experience in children under 1 year is not enough), suppression of GI motility, signs of intestinal obstruction (patients should be under special supervision). Patients with a violation of heart rate and conduction; patients receiving antiarrhythmic drugs and beta-blockers; patients with significant electrolyte imbalance; patients with lengthening or risk of QT prolongation, including patients with electrolyte balance disorders, chronic heart failure, bradyarrhythmia or taking other medicines that may cause prolongation of the QT interval.

Pregnancy and lactation:

Category FDA - B. The drug is contraindicated in breastfeeding and in I trimester of pregnancy.

Dosing and Administration:

Dosing regimen is individual.

Intravenously, intramuscularly, inside, rectally.

Cytostatic therapy: the choice of the dosing regimen is determined by the emetogenicity of antitumor therapy. For adults, the daily dose is usually 8-32 mg. The efficacy of ondansetron can be increased by a single intravenous administration of a glucocorticoid (eg 20 mg dexamethasone) prior to chemotherapy.

To prevent delayed emesis that occurs 24 hours after the initiation of chemotherapy or radiotherapy, it is recommended to continue taking the medication internally at 8 mg every 12 hours or rectally at 16 mg once daily for 5 days.

Children over 2 years old - 5 mg / m² intravenously immediately before the start of the course, followed by oral administration at a dose of 4 mg after 12 hours; after the end of the course it is recommended to continue treatment 4 mg 2 times a day inside within 5 days.

Prevention of postoperative nausea and vomiting: adults - in a single dose of 4 mg intramuscularly or intravenously (slowly) at the beginning of anesthesia or inside at a dose of 16 mg for 1 hour before the onset of anesthesia; children older than 2 years - only parenterally in a single dose of 0.1 mg / kg (maximum to 4 mg) in the form of a slow intravenous injections before or after anesthesia.

Duplication of developed postoperative nausea and vomiting: adults - 4 mg intramuscularly or intravenously; children over 2 years - 0.1 mg / kg (up to 4 mg) intravenously slow.

Intramuscularly in the same body region ondansetron can be administered at a dose not exceeding 4 mg!

With pronounced impairment of liver function, significantly decreases the clearance of ondansetron, increases the half-life of plasma, so do not exceed the daily dose (8 mg).

Side effects:

From the nervous system: headaches, involuntary movements, transient disturbances of vision, dizziness.

From the gastrointestinal tract: diarrhea, abdominal pain, constipation, transient increase in the level of transaminases in the serum.

From the cardiovascular system: Arterial hypertension, chest pain, bradycardia, arrhythmias.

Other: flushes of blood to the head and epigastric region, bronchospasm, anaphylactic reactions, angioedema.

Overdose:

Constipation, hypotension, transient AV block II degree, amaurosis, weakness.

Treatment is symptomatic.

Interaction:

Allopurinol, antidepressants (MAO inhibitors), valproic acid and its salts, verapamil, diltiazem, disulfiram, isoniazid, ketoconazole, lovastatin, macrolides, metronidazole, omeprazole, propranolol, fluconazole, fluoroquinolones, quinidine, quinine, chloramphenicol, cimetidine, estrogen-containing oral contraceptives (inhibitors of cytochrome P450 isoenzyme 2D6, 3A) increase the toxicity of ondansetron.

Barbiturates, glutethimide, griseofulvin, dinitrogen oxide, carbamazepine, carisoprodol, papaverine, rifampicin, tolbutamide, phenylbutazone, phenytoin (and possibly other hydantoins) decrease the effectiveness of ondansetron.

Dexamethasone with a single intravenous dose of 20 mg before the start of chemotherapy increases the effectiveness of ondansetron.

When vanundanib was used together with ondansetron, an insignificant additive effect on the QTc interval prolongation was observed (approximately 10 msec), therefore, the concomitant use of these medicines Not recommended. In the case of ondansetron with vandetanib, careful monitoring is requiredconcentration of electrolytes in serum and ECG, as well as intensive therapy of any disorders.

It should avoid the use of toremifene with ondansetron (may extend the interval QT). If ondansetron is needed, it is recommended to interrupt toremifene therapy. If interruption of treatment with toremifene is not possible, careful monitoring ECG.

Special instructions:

With severe liver damage, the dose should not exceed 8 mg per day.

It should be special observation of patients with symptoms of sub-acute intestinal obstruction (due to increased transit time through the colon).

Impact on the ability to drive vehicles and manage mechanisms

Not found.

Instructions

Ondansetron (Ondansetronum)