As the pH of most body fluids is 7.4, products such as injections, eye drops and nasal drops should, in theory, be buffered at this value to avoid irritation.

Many body fluids themselves, however, have a buffering capacity and, when formulating low volume intravenous injections or eye drops, a wide pH range can be tolerated.
This is potentially useful should a compromise be necessary when choosing a pH that is physiologically acceptable for a drug whose optimum stability, solubility and absorption may depend on different pHs.