What is an empty stomach?

Clinical
By
Shani Pickering
-
empty stomach

Food can act as a prompt for medicine administration and be an easy way for patients to incorporate doses into their routines.

Explaining to patients that they should take a medicine on an empty stomach or in a specific way away from food may not always be met with great enthusiasm! Confusion, and not fitting into a patient’s routine where possible, can lead to poor adherence and negative patient outcomes. 

Why does food sometimes matter?

Food, or the absence of it, may significantly impact systemic exposure, safety, tolerability and effectiveness of a medicine, depending on its pharmacokinetics and adverse effects.

Take alendronate for example – the product information (PI) recommends taking it at least 30 minutes before the first food of the day as its bioavailability is negligible when taken with or up to 2 hours after a meal.1,2

Why do some PIs have a differing definition of an ‘empty stomach’?

This may stem from Food and Drug Administration (FDA) guidance in America, where many medicines are first introduced to the market.

FDA guidance for medicine sponsors suggests that if a medicine needs to be taken in fasted conditions, studies using an overnight fast of at least 10 hours before medicine administration, and waiting at least 4 hours after the dose before eating, are optimal. However, this might not be practical for all medicines and patients. It is then up to the medicine’s sponsor to provide pharmacokinetic data to support pragmatic and realistic dosing instructions for patients to separate food and medicine administration. Sponsors can use modified fasting conditions with differing separation times, and must consider frequency of medicine dosing, the likely demographics of the patient, the condition being treated and any other relevant factors.3 These could vary significantly between different medicines!

Why does CAL 3b say something different to the PI?

The Australian Pharmaceutical Formulary and Handbook (APF) considers that an empty stomach for the purposes of medicine absorption is ‘at least half an hour before food or two hours after food’, as reflected in the wording of Cautionary Advisory Label (CAL) 3b.4,5

This standardised approach is to ensure medicine instructions are simplified and practical for patients, and may differ from the medicine’s PI. Remember, CALs are intended to be used as an adjunct, not a replacement, to verbal counselling.5

Consider adherence and use professional judgement when providing advice on dose administration.

This may require weighing up optimal dose timing and adherence if a patient can’t easily accommodate the timing of doses, particularly when treating chronic conditions.4

References

  1. Therapeutic Goods Administration. Fosamax Plus Product Information. 2024. At: www.tga.gov.au/resources/artg/136846
  2. Alendronate. Martindale: The Complete Drug Reference; [updated 30 Oct 2024]. At: www.medicinescomplete.com/#/content/martindale/22524-r?hspl=alendronate#content%2Fmartindale%2F22524-r%2319721-a3-v
  3. US Food and Drug Administration. Assessing the effects of food on drugs in INDs and NDAs – clinical pharmacology considerations: guidance for industry. 2022. At: www.fda.gov/media/121313/download
  4. Grannell, L. When should I take my medicines? Aust Prescr 2019;42:86–9.
  5. Sansom LN, ed. Cautionary advisory labels Explanatory notes. Australian pharmaceutical formulary and handbook; [updated 2024 Jul 24]. At: https://apf.psa.org.au/dispensing-and-labelling/cautionary-advisory-labels/explanatory-notes