Indometacin is well known as local eye drug for the prevention of cystoid macular oedema. The concentration is 50mg/5ml. Another inhibitor of the prostaglandin synthesis is flurbiprofen; its concentration is 1.5mg/5ml. Indometacin is a suspension and available in different concentrations dependent on the shaking procedure. We measured the concentration of indometacin in one single eyedrop from a full bottle, half full and a nearly empty bottle. After correct shaking the concentration of indometacin was between 48 and 53mg/5ml.