Ranitidine

BRAND NAMES:

Zantac – Zantac is available in tablets and syrups which contain ranitidine hydrochloride as the active ingredient. It is available in strengths of Zantac 150 mg, 300 mg tablets, Zantac 25 effervescent tablets, and Zantac syrup.

Wal-zan – It is a composition of ranitidine hydrochloride available in tablets as Wal-zan 150 mg.

MECHANISM OF ACTION:

Ranitidine lowers gastric acid output by reducing the effect of histamine on histamine H2-receptors on the stomach wall's parietal cells. Histamine is a chemical transmitter that causes parietal cells to release stomach acid. Ranitidine inhibits histamine's effect by inhibiting H2 receptors, lowering stomach acid output.

PHARMACOKINETICS:

Absorption: The bioavailability of ranitidine is about 50-60%. It takes 1 -3 hours to reach its peak concentration.

Distribution: The volume of distribution of ranitidine is 1.4 L/Kg.

Metabolism: N-oxide is the major metabolite present in the urine which represents less than 4% of the dose. Ranitidine includes other metabolites S-oxide and desmethyl ranitidine.

Excretion: It is mainly excreted through urine and the remaining through feces.

PHARMACODYNAMICS:

Ranitidine inhibits the release of stomach acid triggered by food and other medicines by reversibly binding to histamine receptors on gastric parietal cells.

DOSAGE AND ADMINISTRATION:

Ranitidine is available in tablets, injections, and syrups.

For Gastroesophageal reflux disease 

• In adults, the recommended dose is 150mg orally every 12 hours or 50mg intramuscular/intravenously every 6 – 8 hours.

• Oral dosage for children ages one month to sixteen years is 5–10 mg/kg day, divided every 12 hours, with a daily maximum of 300 mg. The recommended intravenous dose is 2-4 mg/kg/day every 6 hours, with a maximum of 50 mg/dose or 200 mg/day.

For treating gastric ulcers, 

• In adults, the dose starts with 150mg orally for every 6 hours or 50mg intramuscular / intravenously for every 6-8 hours.

• In children the recommended dose is 4 – 8mg/kg orally every 12 hours, and should not exceed 300 mg/day. 2 -4 mg/kg/day is recommended intravenously for every 6-8 hours and should not exceed 50 mg/dose or 200mg/day.

In Hypersecretory conditions, the drug recommended is 150 mg orally every 12 hours. 50 mg intramuscular or intravenous bolus or infusion every -8 hours, not exceeding 40 0mg/day, 6.25 mg/hour continuous infusion.

CONTRAINDICATIONS:

It is contraindicated in patients with hypersensitivity to the drug or any of its components, gastric cancer, and hepatitis disease.

DRUG INTERACTIONS:

When taking ranitidine some medication in order should be avoided to decrease adverse effects. If it is mandatory to take the drugs that have been already used for other treatments then it's important to discuss with the doctor before taking them. Below are the few medications where ranitidine can interact

•   Anticoagulants -  Warfarin, Aspirin

•   Antifungals – Ketoconazole, Fluconazole

•   Cancer medicines – Dasatinib, Bosutinib, pazopanib, erlotinib, neratinib.

•   Hepatitis medicines – Loperamide, metformin, multivitamins, theophylline, sofosbuvir.

FOOD INTERACTIONS:

Avoid alcohol and tobacco to avoid dehydration.

ADVERSE EFFECTS:

•   Agitation

•   Hypersensitivity

•   Dizziness

•   Confusion

•   Abdominal pain

•   Anemia

•   Muscle and joint pains

•   Hair loss

•   Constipation

•   Inflammation of small intestines

•   Pancreatitis

•   Deficiency of platelets

TOXICITY:

Overdose of ranitidine can cause some toxic effects 

•   Gait abnormalities

•   Hypotension

•   Bradycardia

•   Tachycardia

•   Vomiting

•   Diarrhea