Nocturnal gastric acidity and acid breakthrough on different regimens of omeprazole 40 mg daily

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Abstract
On chronic intake of omeprazole, most healthy volunteers and patients still have nocturnal acid breakthrough (NAB), defined as night-time periods with gastric pH < 4.0 lasting for longer than 1 h. Gastro-oesophageal reflux during NAB may be particularly injurious to the oesophageal mucosa, contributing to the chronic lesions complicating the condition. To compare the effect of three different dosing regimens of omeprazole 40 mg daily with regard to suppressing nocturnal gastric acidity and avoiding NAB. Eighteen healthy volunteers were given three different regimens of omeprazole for 7 days each in randomized order: 40 mg before breakfast (qAM), 40 mg before dinner (qPM) and 20 mg before breakfast and dinner (b.d.). On day 7, 24-h intragastric and intra-oesophageal pH-metry was performed. Tracings were analysed for the period from 22.00 h until 06.00 h with regard to the percentage of time at which gastric pH was below 4.0, 3.0 and 2.0, and also the occurrence and duration of NAB. Nocturnal acid breakthrough was significantly more common on qAM than on qPM and b.d. (P < 0.05) dosing. The percentage of time gastric pH was less than 4.0 overnight was significantly lower on qPM (median 31.3) and b.d. (median 20.5) than on qAM (median 66.3) dosing (P = 0.01 and P < 0.02, respectively). A pH threshold of 3 and 4 showed the same differences, as did median 24-h gastric pH. Daytime acidity was not significantly different. In healthy volunteers, dinner time or split dosing of omeprazole 40 mg daily is significantly more effective than dosing before breakfast in preventing NAB and controlling gastric acidity. These regimens should be preferred in patients in whom suppression of nocturnal gastric acidity is desirable.