Heartburn is a painful burning sensation experienced in the upper stomach and chest due to the reflux of stomach acid in the oesophagus.
This reflux is caused by the relaxation of lower oesophageal sphincter (LES) which normally guards the stomach entrance but in certain conditions, gives way to the acid to flow back up.
Poor diet and improper lifestyle are the common triggers of relaxation of LES but there can be other factors involved too.
Heartburn is a relatively common disorder which can be treated with simple medications and herbs.
Negligence of this condition can lead to a chronic and more severe problem called gastro-oesophageal reflux disease (GERD).
H2 antagonists for heartburn treatment
H2 blockers or H2 antagonists are the histamine type 2 receptor analogs that block these receptors in the stomach and inhibit the release of acid.
As compared to antacids, they are a little slow in their action and take about 30-90 minutes to be in full action.
Despite their slow effects, they are effective for a long time and are preferred for a higher level of heartburn, acidity and ulcers which cannot be treated by antacids.
H2 antagonists have a high efficacy and can stop 24 hour acid secretion in the stomach by up to 70%.
They are majorly used in treatment of nocturnal acid secretion which is the cause of most heartburns and peptic ulcers.
There are a number of compounds that act as H2 receptor antagonistic agents but four of them are majorly used in medications namely famotidine, cimetidine, ranitidine and nizatidine .
Famotidine
Famotidine is a common ingredient of many H2 receptor antagonistic medications available both by prescription and over the counter.
It is available in the form of tablets and syrups but the tablet form is more common. T
he tablets of 20 to 40 mg are available in generic (drugs with same composition and effects as some other brand) or parenteral (available for intravenous infusion or injection) forms in pharmacies.
Over the counter formulations are available in the form of gelcaps or tablets of 10 to 20 mg.
Famotidine is metabolised in the liver by cytochrome P450 system which is responsible for detoxification of many drugs and chemicals in the body, hence its toxicity and side effects are relatively low .
However, it still can cause mild headache, confusion, dizziness, diarrhoea and constipation.
Some serious side effects that need to be reported immediately include hoarseness in voice, difficulty in swallowing, swelling, hives and rashes.
Medications containing famotidine are usually taken once or twice a day, especially at bed time.
To prevent symptoms, it is taken about 15-60 minutes before meals or consumption of food or drinks that can cause heartburn.
Over the counter medications containing famotidine should not be taken more than twice (2 tablets) in 24 hours.
The course of medication should not be extended beyond 2 weeks without medical supervision whether or not the symptoms are improving .
Cimetidine
It is another common H2 blocker, widely used in several prescription and over the counter medications.
In prescription tablets, it is available in 200, 300, 400, and 800 mg in several generic and oral or parenteral forms, commonly sold with the brand name Tagamet.
Over the counter medications are of 200 mg. It is taken about 30 minutes before meals to prevent symptoms.
Common dosage of cimetidine containing tablets is 200-400 mg twice daily or 800 mg once at bed time taken with 6 to 8 ounces of water, for up to 8 weeks and maintenance dose is 400 mg daily.
Over the counter medications are to be taken once or twice daily for not more than 2 weeks without prescription.
Cimetidine is also metabolized in the liver by cytochrome P450 pathway but it can interfere with the metabolism of other compounds through this pathway due to its reactivity and hence can cause significant drug to drug interactions when taken with medications containing warfarin, digoxin, contraceptives, isoniazid and phenytoin .
It can usually cause mild side effects such as headache, dizziness, drowsiness, diarrhoea and breast enlargement.
Effects such as confusion, hives, hallucination, nervousness and excitement can be dangerous and require immediate medical attention .
Ranitidine
Ranitidine was the second H2 antagonistic chemical after cimetidine to be included in commercial medications.
It is available in 150 and 300 mg tablets in generic forms for both oral and parenteral administration.
Over the counter formulations are available usually in a composition of 75 mg each. A famous brand name containing ranitidine is Zantac which is an over the counter medication.
It is like other H2 antagonists, taken about 30-60 minutes before meals. Typical dose of ranitidine containing prescription tablets is 150 mg twice daily or 300 mg once at bed time for 4-8 weeks.
Maintenance therapy is done by taking 150 mg once daily. Over the counter preparations are to be taken once or twice daily for not more than 2 weeks.
Ranitidine is also metabolized in liver by cytochrome P450 pathway but it does not interfere with the intermediates of the system like cimetidine and thus is not harmful and is less likely to cause any serious drug to drug interactions .
Common side effects include headache, nausea, vomiting and stomach pain .
Nizatidine
This is usually taken to cure stress ulcers and stress induced gastro oesophageal reflux disease.
It is available in the concentrations of 150 and 300 mg in generic forms for both oral and parenteral administration.
Over the counter preparations contain usually 75 mg of nizatidine . It is widely available by the brand name Axid (prescription) and Axid AR (OTC).
Its dosage is similar to that of ranitidine and is to be taken 30-60 minutes before meals or at bed time.
If taking the medication over the counter, its course should not be extended beyond 2 weeks without prescription.
It is less likely to cause any major metabolic side effects or toxicity. Common side effects may include diarrhoea, vomiting, headache, runny nose, cough, stomach pain, sneezing and sweating .
Common H2 blockers available for heartburn treatment
Pepcid and Pepcid AC: both the drugs contain famotidine as an active ingredient. Pepcid AC is an OTC drug.
It should be taken in a dose of 1 tablet with a glass of water. It is strictly to be swallowed and not chewed.
For children above 12 years and adults, it should be taken 10-60 minutes before eating food or drinking beverages that cause heartburns.
It should never be given to children below 12 years of age without prescription .
A prescription drug containing famotidine manufactured by the same brand is called Pepcid.
The recommended oral dose in adults is 20 mg for up to six weeks and for those with chronic heartburn including ulceration and oesophageal erosion, the dose is followed up to 12 weeks.
For paediatric patients of ages 1-16 years, the dose kept is 2 mg/kg/day .
Fluxid: it also contains famotidine as an active ingredient and is a prescription medication. It should be taken in a dose of 1 tablet by keeping on tongue as it is an orally disintegrating tablet and doesn’t need any fluid for swallowing.
For children above 12 years and adults, ideal dose is 40 mg to be taken once during bedtime and for maintenance, 20 mg a day at bedtime .
Tagamet and Cimetidine hydrochloride: both the drugs contain cimetidine as an active ingredient.
Tagamet is an OTC drug and Cimetidine hydrochloride is a prescription medication.
Tagamet is taken by swallowing one tablet with a glass of water right before or anytime up to 30 minutes before eating food or drinking any beverages that cause heartburn.
The dose should not be exceeded beyond 2 tablets in 24 hours and children should not be given this without prescription .
Cimetidine hydrochloride: is available in the form of syrups/injection fluids and is used to treat diagnostically (via endoscopy) confirmed GERD.
The recommended dose is 1200 mg divided in a day (800 mg two times or 400 mg 4 times) for 12 weeks to heal heartburn and maintain the effects.
The results of use of cimetidine beyond 12 weeks have not been established .
Axid/Axid AR: the tablet contains nizatidine as an active ingredient and is available as an OTC drug.
For adults and children above 12 years of age, it is taken right before eating or anytime before 60 minutes of eating or drinking anything that can cause heartburn.
The dose should not be exceeded beyond 2 tablets in 24 hours and children below 12 years of age should not be given this drug without prescription.
Nizatidine capsule: as the name suggests, it contains nizatidine and is a prescription drug. It is taken by swallowing 1 tablet (with a concentration of 150 mg) with a glass of water twice a day.
It is given up to 8 weeks up till the treatment of symptoms and then it is taken in a dose of 150 mg once per day as a maintenance therapy .
Zantac: it contains ranitidine hydrochloride as an active ingredient and is an OTC medicine. It is taken in a dose of 150 mg or 10 mL of syrup (2 teaspoonfuls) twice daily .
Zantac is also available as tablets which can be taken in a dose of 1 tablet with a glass of water to relieve symptoms or 30-60 minutes before eating or drinking to prevent symptoms .
Dosage and consumption
H2 Blockers are usually taken 30-60 minutes before meal twice daily or at bed time once daily or as indicated by the doctor.
For prescription drugs, the instructions provided by the doctor should be strictly followed.
For OTC drugs, the proper dose is given in the label and the medication should be consumed according to what is indicated.
Occurrence of any disorder or exacerbation of the symptoms should be reported immediately.
OTC drugs should not be consumed beyond 2 weeks without prescription.
If a dose is missed, it should not be compensated by taking two doses at one time .
Side effects and precautions
Each H2 antagonist comes with its own set of precautions in diet and other medications which is indicated on the label and by the doctor if it’s taken by prescription.
All the instructions should always be followed to avoid any unwanted side effects.
Normally, H2 antagonists are safe to take but they can pose significant side effects if the patient is having any other disorder for which the medications are taken regularly because H2 blockers can interact with other drugs and their metabolism.
Thus, in such a case, H2 antagonists should never be taken without prescription and the doctor should be clearly informed about all other drugs being consumed.
Some of the other common side effects that H2 antagonists cause are headache, dizziness, vomiting, diarrhoea or constipation.
These effects differ according to the active ingredients of the medication .
Summary
H2 antagonists are effective heartburn relievers. Though showing a late effect, they help in amelioration of heartburn and ulcers for a long time.
They are available both by prescription and over the counter and are safe to take if all the precautions are strictly followed.
For low level heartburn, OTC drugs can provide relief, but for severe heartburn, it is always advised to consult a doctor to avoid any side effect and discomfort in future and for a better treatment.