Published August 9, 2017 (revised December 20, 2024)
Some medicines, including many prescribed for children, come in a powder form. Water must be added to the powder so the medicine can be easily measured and taken. The ratio of water to powder must be precise, so that the prescribed amount of the final liquid mixture provides the correct dose of medicine per milliliter (mL). It is best for the pharmacist to add water right before the medicine is picked up. Once mixed, the medicine often needs to be refrigerated to stay potent. But if the pharmacist forgets to add the water, or if the wrong amount of water is added at home, a serious dosing error can occur.
In one case, a pharmacist forgot to add water to powdered amoxicillin (an antibiotic). The child received 20 times more medicine than the doctor prescribed. The directions said to give 9 mL of medicine for each dose. The child’s father filled a measuring cup with enough powder to reach the 9 mL line, and then gave it to his son in a little water.
In another case, a pharmacist dispensed a carton containing a bottle of azithromycin powder (an antibiotic) for a child without adding water first. The pharmacist checked the label on the carton to make sure it was correct. But she did not open the carton to look at the bottle. So, she did not notice that the powder medicine had not been diluted with water. Thankfully, in this case, the mother returned the medicine to the pharmacy for proper mixing with water before giving any of the medicine to her child.
Parents have also simply added a little water to the bottle of powder medicine and then followed the directions by giving their child carefully measured doses. The problem here is that the amount of water added to the bottle determines how much medicine is in each dose (mL). So, giving 5 mL of medicine that was mixed with a small amount of water will provide a much higher dose than giving 5 mL of medicine mixed with a large amount of water. The amount of water added to the powder medicine must be exact and should be added by a pharmacist.
Here’s what you can do: Here are some clues that the pharmacist has forgotten to add the water to a powder medicine:
When picking up a prescription, open the bag and read the label. If you expect a liquid medicine, shake the bottle to make sure it contains a liquid. Never try to add water to a powder medicine yourself. Bring it back to the pharmacy to have it mixed. The amount of water used must be carefully measured to be sure that each dose has the correct amount of medicine in it. Always double check with your pharmacist before taking or giving medicine if it is a powder.
