When Is The Best Time To Antacids, Acid Blockers And PPI Medications?

In our latest question and answer, the pharmacist discusses the best time to dose over the counter antacid medication including antacids, H2 Blockers and PPIs.

When Is The Best Time To Antacids, Acid Blockers And PPI Medications?
Jan 25, 2018

Bubble asked

Yes, Hello! I am a nursing student studying for my NCLEX. One of my study questions says that you should take H2 blockers with meals and antacids 1 hour after meals. My question is, why does it make a difference when we take these medications with or without food? What happens if we take antacids with food? I guess I'm confused about the mechanisms behind how these medications work. Also with proton pump inhibitors...why should we take those 30 minutes before eating? What's the logic behind that?


TumsHeartburn is a common complaint and oftentimes precludes the consumption (and enjoyment!) of many foods for a variety of individuals. Heartburn generally occurs when acid from the stomach gets backed up into the throat and esophagus.  This often leads to negative symptoms such as indigestion, bloating, burning and pain. In addition, there are numerous disease states associated with this acid reflux such as GERD (gastroesophageal reflux disease) and Barrett's esophagus. Heartburn symptoms tend to happen at night or after a meal and more serious diseases  can form over time.

Fortunately, there are many medications that are useful for the treatment of heartburn and associated symptoms. There three main classes of antacid medications:

  • Antacids (i.e. acid neutralizers)
  • H2 Blockers
  • PPI (Proton Pump Inhibitors)

All medications have their place in therapy and can be extremely beneficial for reducing acid reflux symptoms. Due their their respective mechanisms of action, they typically need to be dosed at a specific time to provide maximum effect.

When To Dose Antacids

Antacids include Tums and Rolaids. These products contain calcium carbonate, which neutralizes stomach acid. Specifically, they neutralize gastric acid and increase the pH of the gastric contents. This helps to reduce gastrointestinal irritation and reduce the symptoms of heartburn. Below are some specifics regarding antacid medications:

  • Antacids are the fastest acting medications for heartburn. They typically work as soon as a few minutes after consumption.
  • Antacids are short acting. Once all of the medication has been used to neutralize acid, they are no longer effective. Generally antacids last for 1 to 2 hours.
  • They are best dosed with meals or about 30 minutes to 1 hour after eating. Antacids are only effective when there is acid to neutralize (which is brought on by food consumption etc...). As antacids don't last a long time, they aren't very effective if taken before food.
  • In addition to calcium carbonate products, antacids with aluminum and magnesium are available as well.
When To Dose H2 Blockers

H2 blockers include Zantac (ranitidine), Pepcid (famotidine) and Tagamet (cimetidine). H2 blockers block the binding of histamine to receptors on parietal cells (acid producing cells) in the stomach and therefore work by reducing acid secretion. Not only do H2 blockers block acid secretion continuously, they also block acid secretion in response to food. Below are some specifics regarding antacid medications:

  • H2 blockers don't work as fast as antacids but last longer, up to 12 hours per dose.
  • Some H2 blockers come in combination with antacids, for both immediate and long term relief (e.g. Pepcid Complete).
  • H2 blockers can generally be dosed with meals or before.  The onset of action of most H2 blockers is typically within 1 hour after administration. They are not very effective if taken only when symptoms begin to occur.
When To Dose PPIs
PPI (Proton Pump Inhibitors) include Prilosec, Prevacid and Nexium.  PPI medications block acid production through inhibition of the H+/K+ ATPase enzyme "pump".  An important clinical fact regarding PPI medications is that they only inhibit actively secreting pumps. In other words, the acid pumps must be stimulated (e.g. from food) in order to be blocked.  Below are some specifics regarding antacid medications:
  • PPI medications are potent and generally last longer than H2 blockers. They appear to more effective in the treatment of GERD and related symptoms.
  • PPI medications are best taken 30 minutes to one hour before food on an empty stomach.  This allows time for the drug to be absorbed and ready to work when food is consumed, which activates acid secretion (PPIs only work on active pumps).
  • While PPI medications are effective, they generally are not recommended for routine use over the counter due to the increased risk of side effects versus other over the counter options.
Administration Time Summary
  • Dose antacids with meals or when symptoms begin  (generally around 1 hour after food).
  • Dose H2 blockers before meals or with food. They take about 1 hour to begin working.
  • Dose PPI medications 1 hour before food. They need to be absorbed and ready to work when acid secretion begins as they only inhibit active pumps.

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