Medication should never replace good management, but sometimes a treatment is unavoidable. In poultry and pigs, medication is often administered via the drinking water. The water quality largely determines how successful the administration will be. The water composition influences the solubility and biological availability of the medication and can even have an influence on the efficacy. Hardness, pH, iron and cadmium levels are some important parameters that can interfere with the medication. This counts for medicines in general, but is of particular importance for antibiotics because partial inactivation of the antibiotic can cause antibiotic resistance. The following should be kept in mind when using antibiotic water medication:
Ampicillin/amoxicillin need a neutral to basic pH to dissolve well. They are sensitive to temperature swings and to the enzyme ‘beta lactamase’ that can be produced be bacteria present in the drinking water system (biofilm!).
Tetracycline’s are poorly soluble. Calcium in hard water forms complexes with tetracycline’s. These complexes are poorly absorbed in the digestive tract. Acidification of the water can improve the solubility as well as the absorption.
Sulphonamides can be captured by organic substances.
Most antibiotics are unstable in solution (e.g. amoxicillin solution: shelf life 6h). They should be administered in an appropriate volume of water so that the animals drink everything in time.
These examples illustrate the importance of water quality when administering antibiotics. For each specific antibiotic treatment via the water, the compatibility of the antibiotic with the drinking water (and water treatment products!) should be discussed with the advising veterinarian.