Name of the H2 blockers Drugs
- Ranitidine
- Famotidine
- Nizatidine
- Cimetidine
1.Ranitidine
| Ranitidine |
| Availability: Capsules (liquid-filled): 150 mg, 300 mg Solution for injection: 25 mg/ml in 2-, 6-, and 40-ml vials Solution for injection (pre-mixed): 50 mg/50 ml in 0.45% sodium chloride Syrup: 15 mg/ml Tablets: 150 mg, 300 mg Tablets (effervescent): 150 mg |
| Indications and dosages Active duodenal ulcer Adults: 150 mg or 10 ml P.O. b.i.d., or 300 mg or 20 ml P.O. daily, or 50 mg I.V. or I.M. q 6 to 8 hours To maintain healing of duodenal ulcers Adults: 150 mg or 10 ml P.O. Benign gastric ulcer Adults: 150 mg or 10 ml P.O. b.i.d. For maintenance, 150 mg or 10 ml P.O. or 50 mg I.V. or I.M. q 6 to 8 hours Active duodenal and gastric ulcers Children ages 1 month to 16 years: 2 to 4 mg/kg/day P.O., up to a maximum of 300 mg/day To maintain healing of duodenal and gastric ulcers Children ages 1 month to 16 years: 2 to 4 mg/kg/day P.O., up to a maximum of 150 mg/day Erosive esophagitis Adults: 150 mg or 10 ml P.O. q.i.d. Children ages 1 month to 16 years: 5 to 10 mg/kg P.O. daily in two divided doses Gastroesophageal reflux disease Adults: 150 mg or 10 ml P.O. b.i.d. Children ages 1 month to 16 years: 5 to 10 mg/kg P.O. daily in two divided doses Pathologic hypersecretory conditions, including Zollinger-Ellison syndrome Adults: 150 mg or 10 ml P.O. b.i.d., adjusted according to patient’s needs. In severe cases, up to 6 g/day may be needed. Continue therapy as long as indicated. Hospitalized patients with pathologic hypersecretory conditions, including Zollinger-Ellison syndrome; intractable duodenal ulcers; patients who can’t receive oral drugs Adults: 50 mg I.M. q 6 to 8 hours, or 50 mg intermittent I.V. bolus q 6 to 8 hours, or 50 mg intermittent I.V. infusion q 6 to 8 hours. Children ages 1 month to 16 years: 2 to 4 mg/kg/day I.V. in divided doses q 6 to 8 hours, up to a maximum of 50 mg q 6 to 8 hours. |
Mechanism of Action :
Reduces gastric acid secretion and increases gastric mucus and bicarbonate production, creating a protective coating on gastric mucosa
Administration
- For intermittent I.V. bolus injection, dilute in normal saline solution or other compatible solution to a concentration not exceeding 2.5 mg/ml.
- Inject no faster than 4 ml/minute (5 minutes).
- For continuous I.V. infusion in patients with Zollinger-Ellison syndrome, add to dextrose 5% in water (D5W) or other compatible solution; dilute to a concentration not exceeding 2.5 mg/ml, and start infusion at 1 mg/kg/hour. After 4 hours, if measured gastric acid output exceeds 10 mEq/hour or symptoms occur, increase dosage in increments of 0.5 mg/kg/hour, and remeasure acid output.
- Give P.O. doses with or without food. Give once-daily dose at bedtime.
- For intermittent I.V. infusion, dilute in D5W or other compatible solution to a concentration not exceeding 0.5 mg/ml. Infuse no faster than 7 ml/ minute (15 to 20 minutes).
- Be aware that premixed Zantac solution of 50 mg in half-normal saline solution (50 ml) doesn’t require dilution. Infuse over 15 to 20 minutes.
- Know that I.V. form may be added to total parenteral nutrition solutions.
- Inject I.M. undiluted deep into large muscle
Contraindications
- Hypersensitivity to drug or its components
- Alcohol intolerance (with some oral products)
- History of acute porphyria
Precautions :
- Renal or hepatic impairment, heart rhythm disturbances, phenylketonuria (effervescent tablets)
- Elderly patients
- Pregnant or breastfeeding patients.
Adverse reactions
- CNS: headache, agitation, anxiety
- GI: nausea, vomiting, diarrhea, constipation, abdominal discomfort or pain
- Hematologic: reversible granulocytopenia and thrombocytopenia
- Hepatic: hepatitis
- Skin: rash
- Other: pain at I.M. injection site, burning or itching at I.V. site, hypersensitivity reaction
Patient monitoring
- Assess vital signs.
- Monitor CBC and liver function tests
Patient teaching
- Tell patient he may take oral drug with or without food. Advise him to take once-daily prescription drug at bedtime.
- Instruct patient to dissolve EFFER dose in 6 to 8 oz of water before taking.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- Tell patient smoking may decrease drug effects.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.
Pharmacokinetics
- Bioavailability: 50% (PO); 90-100% (IM)
- Protein bound: 10-19%
- Metabolism: liver
- Half-life: 2.5-3 hr (PO; increases to 4.8 hr with CrCl 25-35 mL/min); 2-2.5 hr (IV)
- Peak serum time: 15 min (IM); 2-3 hr (PO)
- Excretion: Urine (30% PO; 70% IV)
2.Famotidine
| Famotidine |
| Availability: Gelcaps: 10 mg Oral suspension: 40 mg/5 ml Solution for injection: 10 mg/ml, 20 mg/50 ml of normal saline solution Tablets: 10 mg, 20 mg, 40 mg Tablets (chewable): 10 mg Tablets (orally disintegrating): 20 mg, 40 mg |
| Indications and dosages Active duodenal ulcers and benign gastric ulcers Adults: 40 mg P.O. once daily at bedtime or 20 mg P.O. b.i.d. for up to 8 weeks Prophylaxis of duodenal ulcers Adults: 20 mg P.O. once daily at bedtime Gastroesophageal reflux disease Adults: 20 mg P.O. b.i.d. for up to 6 weeks. Maximum dosage is 40 mg b.i.d. for up to 12 weeks. Children ages 1 to 16: 1 mg/kg P.O. daily in two divided doses, to a maximum of 40 mg b.i.d. Infants ages 3 months to 1 year: 0.5 mg/kg P.O. b.i.d. for up to 8 weeks Infants younger than age 3 months: 0.5 mg/kg P.O. once daily for up to 8 weeks Gastric hypersecretory conditions (such as Zollinger-Ellison syndrome) Adults: Initially, 20 mg P.O. q 6 hours, increased as needed to 160 mg q 6 hours Hospitalized patients with pathologic hypersecretory conditions or ulcers; patients who can’t take oral drugs Adults: 20 mg I.V. q 12 hours Prevention or treatment of heartburn, acid indigestion, and sour stomach (Pepcid AC only) Adults: For prevention, 10 mg P.O. 1 hour before eating, or 10-mg chewable tablet 15 minutes before eating, to a maximum of 20 mg/24 hours for up to 2 weeks. For symptomatic treatment, 10 mg P.O. once or twice daily |
Mechanism of Action :
Blocks action of histamine at histamine2-receptor sites in gastric parietal cells, inhibiting gastric acid secretion and stabilizing pepsin
Pharmacokinetics
- Bioavailability: 40-45% (PO; minimal 1st-pass metabolism)
- Protein bound: 15-20%
- Metabolism: liver
- Half-life: 2.5-4 hr (adults; increases with renal impairment, eg, 20 hr with CrCl <10 mL/min); 3-4 hr (children); 4.5 hr (infants 3-12 months); 8-10.5 hr (infants < 3 months)
- Peak plasma time: IV, 20 min; PO, 1-4 hr
- Excretion: Urine (25-30% as unchanged drug when administered PO; 70% when administered IV)
Administration
- Be aware that drug usually is given in one daily dose to patients with renal insufficiency.
- Give P.O. form with foods or liquids.
- Dilute I.V. form with 10 ml dextrose 5% in water or normal saline solution (100 ml) for I.V. piggyback administration.
- Deliver by I.V. push over 2 minutes or intermittent infusion over 30 minutes.
- Know that drug may cause transient irritation at I.V. site.
Contraindications
- Hypersensitivity to drug or other histamine2-receptor antagonists
Precautions :
- Renal impairment with prolonged QT interval and seizures (very rare)
- Rlderly patients
- Pregnant or breastfeeding patients.
Adverse reactions
- CNS: dizziness, headache, paresthesia, asthenia, fatigue, insomnia, somnolence, psychic disturbances
- CV: palpitations, arrhythmias, AV block
- GI: nausea, vomiting, diarrhea, constipation, dry mouth, anorexia, cholestatic jaundice, abdominal pain
- GU: decreased libido
- Hematologic: agranulocytosis, pancytopenia, leukopenia, thrombocytopenia (rare)
- Hepatic: liver enzyme abnormalities, hepatitis
- EENT: orbital edema, conjunctival redness, tinnitus
- Musculoskeletal: musculoskeletal pain, muscle cramps, arthralgia
- Respiratory: bronchospasm, interstitial pneumonia
- Skin: flushing, acne, dry skin, rash, urticaria, alopecia, pruritus; epidermal necrolysis and Stevens-Johnson syndrome (very rare)
- Other: altered taste, fever, pain at injection site, hypersensitivity reactions including anaphylaxis and angioedema
Patient monitoring
- Assess patient for GI signs and symptoms.
- Monitor blood urea nitrogen and creatinine levels in patients with renal impairment.
- Monitor patient for prolonged QT interval and seizures, which have been reported very rarely in patients with impaired renal function whose famotidine dosage or dosing interval may not have been adjusted appropriately. Also monitor patient for arrhythmia and AV block.
- Monitor patient for signs and symptoms of epidermal necrolysis, Stevens-Johnson syndrome, and hematologic or respiratory changes.
Patient teaching
- Tell patient that drug is most effective when taken at bedtime.
- Inform patient that pain relief may not begin until several days after therapy starts.
- Instruct patient to take drug exactly as prescribed and to immediately report cardiovascular signs and symptoms, seizures, and hematologic or respiratory changes.
- Tell female patient to inform prescriber if she is pregnant or breastfeeding.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the tests mentioned above
3.Nizatidine
| Nizatidine |
| Availability: Capsules: 150 mg, 300 mg Oral solution: 15 mg/ml Tablets: 75 mg |
| Indications and dosages Active duodenal ulcer Adults: 300 mg P.O. daily at bedtime or 150 mg b.i.d. for up to 8 weeks Maintenance of healed duodenal ulcers Adults and children ages 12 and older: 150 mg P.O. daily at bedtime for up to 1 year Esophagitis and associated heartburn caused by gastroesophageal reflux disease (GERD) Adults: 150 mg P.O. b.i.d. for up to 12 weeks Active benign gastric ulcer Adults: 150 mg P.O. b.i.d. or 300 mg P.O. once daily at bedtime Erosive esophagitis; GERD Children ages 12 and older: 150 mg P.O. b.i.d. for up to 8 weeks |
Mechanism of Action :
Inhibits histamine action at H2-receptor sites in gastric parietal cells, reducing gastric acid secretion and pepsin production
Pharmacokinetics
- Bioavailability: 48-50% (PO); 90-100% (IM)
- Protein bound: 15%
- Metabolism: Liver, unlike cimetidine, nizatidine does not inhibit microsomal enzymes
- Half-life: 2.5-3hr (PO); 2-2.5hr (IV)
- Peak plasma time: 2-3hr (PO); <15 min (IM)
- Excretion: Urine: 30% (PO); 70% (IV) ,Feces: <6%
Administration
Give with or without food.
If patient is to take drug twice daily, give one dose in morning and one at bedtime.
Contraindications
Hypersensitivity to drug or other H2-receptor antagonists
Precautions :
- Mild renal impairment
- Elderly patients
- Pregnant or breastfeeding patients
- Children younger than age 12 (safety and efficacy not established).
Patient monitoring
- Monitor liver and renal function tests.
- Check temperature; watch for fever and other signs and symptoms of infection.
Patient teaching
- Advise patient to take once-daily dose at bedtime with or without food, or twice-daily doses in morning and at bedtime. Instruct patient to take exactly as prescribed. Caution him not to take other OTC drugs (especially aspirin).
- Tell patient to report signs and symptoms of infection.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.
4.Cimetidine
| Cimetidine |
| Availability: Oral liquid: 200 mg/5 ml, 300 mg/5 ml Tablets: 200 mg, 300 mg, 400 mg, 600 mg, 800 mg |
| Indications and dosages Active duodenal ulcer (short-term therapy) Adults and children older than age 16: 800 mg P.O. at bedtime, or 300 mg P.O. q.i.d. with meals and at bedtime, or 400 mg P.O. b.i.d. Maintenance dosage is 400 mg P.O. at bedtime Active benign gastric ulcer (short-term therapy) Adults and children older than age 16: 800 mg P.O. at bedtime or 300 mg P.O. q.i.d. with meals and at bedtime Gastric hypersecretory conditions (such as Zollinger-Ellison syndrome); intractable ulcers Adults and children older than age 16: 300 mg P.O. q.i.d. with meals and at bedtime Erosive gastroesophageal reflux disease Adults and children older than age 16: 1,600 mg P.O. daily in divided doses (800 mg b.i.d. or 400 mg q.i.d.) for 12 weeks Heartburn; acid indigestion Adults and children older than age 16: 200 mg (two tablets of over-the counter product only) P.O. up to b.i.d. Give maximum dosage no longer than 2 weeks continuously, unless directed by prescriber. |
Mechanism of Action :
Competitively inhibits histamine action at histamine2-receptor sites of gastric parietal cells, thereby inhibiting gastric acid secretion
Pharmacokinetics
- Bioavailability: PO: 60-70% (undergoes minimal 1st pass metabolism)
- Protein bound: 15-20%
- Metabolism: Liver, inhibit microsomal enzymes
- Half-life: Adults: 2 hr; increases to 4-5 hr with renal impairment, Infant: 2.1-3.6 hr
- Peak plasma time: IM: 15 min, PO: 45-90 min
- Excretion: Urine: 48-75% ,Feces: 2-3% (<2% in bile)
Administration
Give with meals.
Contraindications
- Hypersensitivity to drug
- Alcohol intolerance
Precautions
- Renal impairment
- Elderly patients
- Pregnant or breastfeeding patients.
Adverse reactions
- CNS: confusion, dizziness, drowsiness, hallucinations, agitation, psychosis, depression, anxiety, headache
- GI: diarrhea
- GU: reversible erectile dysfunction, gynecomastia
Patient monitoring
- Monitor creatinine levels in patients with renal insufficiency or failure.
- Assess elderly or chronically ill patients for confusion (which usually resolves once drug therapy ends).
Patient teaching
- Inform patient with gastric ulcer that ulcer may take up to 2 months to heal. Advise him not to discontinue therapy, even if he feels better, without first consulting prescriber. Ulcer may recur if therapy ends too soon.
- Advise patient not to take over-thecounter cimetidine for more than 2 weeks continuously, except with prescriber’s advice and supervision.
- As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, foods, herbs, and behaviors mentioned above.
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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