Zantac 150 mg Tablets

Brand Name

The medication is marketed under the brand name Zantac, a widely recognized label in the field of gastrointestinal acid reduction and symptom relief.

International Nonproprietary Name (INN)

The active ingredient in this product is identified globally as ranitidine, a name standardized for consistency across international pharmacological practices.

Form of Release

Zantac is available as oral tablets, effervescent tablets, oral syrup, and an injectable solution. Tablets come in strengths of 75 mg, 150 mg, and 300 mg, effervescent tablets match these doses, the syrup provides 15 mg per mL, and the injectable form offers 25 mg per mL, typically in vials or ampules.

Composition

Each tablet of Zantac contains ranitidine hydrochloride as the primary active substance, with dosages of 75 mg, 150 mg, or 300 mg (equivalent to ranitidine base). The formulation includes several inactive ingredients, such as microcrystalline cellulose, which provides structural support, and magnesium stearate, acting as a lubricant. Additional excipients like hypromellose serve as binders, while the effervescent form includes sodium bicarbonate and citric acid for dissolution. The syrup contains sorbitol as a sweetener and sodium benzoate as a preservative, and the injectable solution includes sodium chloride for isotonicity, ensuring stability across all forms.

Pharmacologic Properties

Pharmacodynamics

Zantac functions as a histamine H2-receptor antagonist, exerting its effects by competitively blocking H2 receptors on gastric parietal cells. This inhibition reduces histamine-stimulated gastric acid secretion, decreasing both basal and meal-induced acid output, which elevates intragastric pH and alleviates acid-related irritation. Its selective action provides rapid relief from heartburn and promotes healing in conditions like ulcers by reducing acid-mediated damage to mucosal tissues.

The medication also lowers pepsin secretion indirectly by reducing acid levels, though it does not affect gastrin release or gastric motility significantly. Clinical studies demonstrate its ability to reduce acid secretion by 50–70% within 1–2 hours, with effects lasting up to 12 hours per dose. It lacks anticholinergic or central nervous system effects, focusing solely on gastric acid control. This targeted mechanism supports its efficacy in managing acid-related conditions efficiently.

Pharmacokinetics

Following oral administration, Zantac is absorbed from the gastrointestinal tract, with peak plasma concentrations reached within 2 to 3 hours. Bioavailability averages 50%, reduced by first-pass metabolism, and food does not significantly alter absorption. The drug binds to plasma proteins at approximately 15%, distributing widely to tissues, including the stomach, liver, and kidneys.

Metabolism occurs in the liver via N-oxidation, S-oxidation, and demethylation, forming inactive metabolites like ranitidine N-oxide and S-oxide. The half-life ranges from 2 to 3 hours, supporting once- or twice-daily dosing. Elimination is predominantly renal, with 50–70% excreted unchanged in urine and the remainder as metabolites, with minor fecal clearance via bile, reflecting its dependence on kidney function for clearance.

Indications for Use

Zantac is prescribed for the treatment of active duodenal ulcers in adults, promoting healing and relieving pain within 4–8 weeks. It is also indicated for maintenance therapy in healed duodenal ulcers to prevent recurrence, offering sustained acid suppression. The medication manages gastroesophageal reflux disease (GERD), including erosive esophagitis, addressing heartburn and esophageal irritation.

It treats benign gastric ulcers and provides symptomatic relief in non-erosive GERD or dyspepsia caused by excess acid. Injectable use is indicated for hospitalized patients with pathological hypersecretory conditions like Zollinger-Ellison syndrome or for those unable to take oral medications. Over-the-counter formulations address occasional heartburn, acid indigestion, or sour stomach, making it versatile for both prescription and self-care use.

Contraindications

Zantac is contraindicated in patients with known hypersensitivity to ranitidine, other H2-receptor antagonists, or any formulation component, such as sorbitol in syrup, where reactions could range from rash to anaphylaxis. It is also prohibited in those with porphyria, as it may exacerbate this condition.

Use is restricted in patients with undiagnosed gastrointestinal bleeding, as it may mask malignancy symptoms, requiring diagnostic evaluation first. Severe renal or hepatic impairment does not strictly contraindicate it, but caution is essential. The medication should not be used in neonates or infants under 1 month for injectable forms due to limited safety data. Immediate acid suppression needs unavailable via oral forms also limit its use unless injectable administration is feasible.

Method of Administration and Dosage

Administration Guidelines

The tablets should be taken orally, swallowed whole with water, with or without food, though nighttime dosing enhances overnight acid control. Effervescent tablets require dissolution in water before drinking, and the syrup needs measuring with a provided device. Injectable doses are administered by healthcare professionals intravenously or intramuscularly over 5–20 minutes. Timing aligns with symptom onset or prevention needs for optimal relief.

Dosage for Adults and Children

For adults with active duodenal ulcers, the typical dose of Zantac is 150 mg twice daily or 300 mg once daily at bedtime for 4–8 weeks. Maintenance therapy uses 150 mg once daily. GERD with esophagitis requires 150 mg twice daily for 6–12 weeks, while symptomatic GERD uses 150 mg twice daily for up to 8 weeks. Over-the-counter use is 75–150 mg as needed, up to 300 mg daily. Children aged 1 month–16 years with GERD or ulcers receive 2–4 mg/kg twice daily, up to 150 mg twice daily; infants under 1 month use 2 mg/kg daily for supervised injectable administration.

Dose Adjustment in Specific Conditions

In moderate to severe renal impairment (creatinine clearance below 50 mL/min), doses are reduced to 150 mg once daily or 75 mg twice daily to prevent accumulation. Mild liver dysfunction allows standard dosing, with caution in severe cases due to minor metabolism. Elderly patients or those with mild symptoms may start at 75 mg daily, adjusted by response. Injectable dosing mirrors oral regimens for acute needs, transitioning to oral as soon as possible.

Side Effects

Zantac may cause a variety of side effects, though many patients experience only mild reactions with short-term use. Common issues include headache, dizziness, or diarrhea, often resolving without intervention. Constipation, nausea, or fatigue are also reported, typically transient as the body adjusts.

Less frequent effects include rash, abdominal discomfort, or mild tachycardia, linked to systemic exposure. Rare but serious reactions, such as agranulocytosis, bradycardia, or reversible confusion, require immediate cessation and medical attention, particularly with prolonged use or injectable administration. Elevated liver enzymes or pancreatitis may occur infrequently. Monitoring helps distinguish drug-related effects from underlying conditions.

Overdose

Symptoms of Overdose

Excessive intake of Zantac is unlikely to cause acute toxicity due to its wide therapeutic index, with symptoms limited to amplified side effects like drowsiness, confusion, or tachycardia. Doses up to 6,000 mg have shown no consistent severe pattern, reflecting rapid clearance.

First Aid Measures

In case of overdose, medical consultation is advised, though emergency measures are rarely needed. No specific antidote exists, so treatment focuses on supportive care, such as hydration for diarrhea or monitoring cardiac status. Activated charcoal may limit absorption if given within 1 hour, with recovery typically within 12–24 hours.

Drug Interactions

Effects on Other Medications

Zantac minimally affects cytochrome P450 enzymes, reducing interactions with drugs like warfarin or theophylline. It may decrease absorption of pH-dependent drugs (e.g., ketoconazole) by raising gastric pH, potentially lowering efficacy, requiring spacing by 1–2 hours. Co-use with antacids may reduce bioavailability if taken simultaneously, though this is uncommon.

Drugs like procainamide or midazolam may have slightly increased levels due to minor renal competition, though adjustments are rarely needed. Patients should report all medications to their healthcare provider to manage these minor interactions, especially in chronic use.

Compatibility with Alcohol and Food

Moderate alcohol use does not directly impair efficacy but may worsen acid-related symptoms, suggesting limited intake during therapy. Food does not significantly affect absorption, allowing administration with or without meals, though nighttime dosing without food enhances acid control.

Special Precautions

Use During Pregnancy and Breastfeeding

Zantac is Category B in pregnancy, with no clear fetal harm in limited data, used cautiously if benefits outweigh risks, typically for severe GERD. It passes into breast milk in small amounts, so short-term use is generally safe with monitoring for infant effects, guided by medical advice.

Women of childbearing age should confirm non-pregnant status before starting and discuss risks with their provider during therapy planning.

Impact on Driving and Operating Machinery

The medication may cause dizziness or drowsiness in some patients, suggesting caution with driving or machinery until tolerance is clear. Most individuals resume normal activities once adjusted, but initial use warrants observation for these effects, typically resolving within hours.

Considerations for Elderly and Pediatric Populations

Elderly patients tolerate Zantac well, with renal function monitoring key due to age-related decline, possibly requiring dose adjustment. Children over 1 month can use weight-adjusted dosing safely, while those under 1 month require careful supervision for injectable use due to limited data.