Twenty-four hour ambulatory nasal pH monitoring

The nasal delivery of drugs, both for systemic and local use, is an expandi ng field with many drugs being delivered by this route. It is known that ch anges in pH can affect drug absorption but there is no data regarding intra nasal pH over time. We present the results of 24-h ambulatory nasal pH moni toring in four subjects, each of whom had monitoring on two separate occasi ons. The apparatus consisted of a pH monitor with two electrodes, thus enab ling us to take readings from 1 and 4 cm behind the anterior end of the inf erior turbinate. Measurements were recorded every 6 s by the posterior elec trode and every 30 s by the anterior electrode. The recording apparatus was worn around the subjects waist. Analysis of the results showed that there was no diurnal variation and no significant differences between the subject s. The mean pH from the anterior electrode was higher than that from the po sterior (7.1 versus 6.6). The pH did not fluctuate with daily activities su ch as eating, drinking or sleeping. The results are interesting and may be of importance with regard to the design of formulations for nasal drug deli very systems.