No, distilled water is not considered to be isotonic.
Isotonic solutions have the same osmotic pressure as the fluids in cells, which means they contain similar concentrations of solutes (like salts and sugars) as found in the body. Distilled water, on the other hand, is pure water without any dissolved salts or other solutes. This lack of solutes means that when distilled water is introduced to a biological system, it can cause osmotic pressure imbalances.
When cells are placed in distilled water, water moves into the cells by osmosis to equalize the concentration of solutes inside and outside the cells. This can lead to cell swelling and even bursting in extreme cases. Therefore, while distilled water may be pure and free from contaminants, it does not exhibit the properties of an isotonic solution.