Published: 2 June 2016


Ghosts of Medicines Passed

This article is more than five years old. Some content may no longer be current.

Prescriber Update 37(2): 22

June 2016

Key Messages

  • The remains of controlled-release formulations can appear in the stools.
  • Commonly prescribed medicines can change the colour of urine.

Medicines Appearing in Stools?

A recent report to the Centre for Adverse Reactions Monitoring (CARM) described a patient whose venlafaxine tablets were being passed in the stools fully undigested.

The passing of a seemingly intact medicine may lead patients, carers and healthcare professionals alike to believe the medicine has not been absorbed1,2.

With some controlled-release formulations it is expected that the empty intact shell that housed the medicine ('ghost-pill' or 'ghost-tablet'), or other insoluble formulation parts, will appear in the stools1,2.

This is because controlled-release formulations (tablets, capsules and their parts) are designed to either disintegrate slowly to release the medicine over a predetermined period, or remain intact1.

Medicines that can appear in the stools include (this is not an exhaustive list):

  • Adefin XL (nifedipine)
  • Arrow-Venlafaxine XR and Efexor-XR (venlafaxine)
  • Concerta (methylphenidate)
  • Duride (isosorbide mononitrate)
  • OxyContin (oxycodone)
  • Span-K (potassium chloride).

When prescribing such medicines, make sure patients are aware that remnants of the medicine can appear in their stools and provide reassurance that the active medicine will be released. However, if a patient reports a lack of medicine efficacy, further investigations may be required.

Medicines can Discolour Urine

The colour of urine can be changed by medicines, certain foods and medical conditions3. A detailed history can usually determine the cause3.

There are a number of commonly prescribed medicines that can change the colour of urine (Table 1)3.

Table 1: Examples of medicines that can change the colour of urine3

Colour of Urine Examples
Red Deferoxamine, hydroxocobalamin, ibuprofen, rifampicin, warfarin
Orange Isoniazid, sulfasalazine, riboflavin
Brown Metronidazole, paracetamol (overdose), nitrofurantoin
Black Metronidazole, nitrofurantoin
White Propofol
Blue or Green Methylene blue, amitriptyline, metoclopramide, promethazine, propofol

Check the individual medicine data sheets and/or consumer medicine information (CMI) for more information ( and

  1. Tungaraza TE, Talapan-Manikoth P, Jenkins R. 2013. Curse of the ghost pills: the role of oral controlled-release formulations in the passage of empty intact shells in faeces. Two case reports and a literature review relevant to psychiatry. Therapeutic Advances in Drug Safety 4(2): 63-71.
  2. Tungaraza TE, Talapan-Manikoth P, Eboka YM, et al. 2014. Ghost pill: knowledge and awareness of this phenomenon among health care professionals. International Journal of Basic & Clinical Pharmacology 3(4): 602-607.
  3. Aycock RD, Kass DA. 2012. Abnormal Urine Color. Southern Medical Journal 105(1): 43-47.
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