We report the appearance of 'poppy seed'-like structures found in the aspirated stomach contents and faeces of a 3-month-old infant receiving an omeprazole liquid via nasogastric tube, prepared by dispersing an omeprazole tablet (10 mg MUPS(R)) in water. Electron microscopy and mass spectroscopy indicated that these particles were hollow, dark purple coloured spheres comprising undissolved omeprazole and its degradation products. These observations suggest rapid degradation of omeprazole in the acid stomach contents, with compromised absorption of active drug. Consequently, dispersion of omeprazole in water may be an inappropriate formulation in this setting.