Short-term effects on blood pressure of reducing nitrate metabolism using antibacterial mouthwash in treated hypertensive individuals

A randomised, controlled, cross-over designed trial will be performed. Each participant will complete 2 intervention periods of 3 days each in random order. These will be separated by a 10 to 12 day washout period. The 3 day intervention periods will correspond to use of either an antibacterial mouth wash (20 ml with 2mg/mL chlorhexidine gluconate) or plain tap water (20 ml) to rinse the mouth after brushing teeth. This will be performed twice daily: in the morning after breakfast; and in the evening after dinner. On each occasion participants will wash their mouth with 20 ml of mouthwash or plain tap water by swishing and gargling for 30 seconds, and then spitting out. During one of the 3 day periods participants will use the mouthwash and the other 3 day period they will use plain tap water. The order of the two periods will be random. Adherence to use of the moutwash/water will be established by participant diaries and measurement of nitrate reduction in the mouth. Throughout each 3 day intervention period participants will be asked to measure their blood pressure at home each day in the morning (shortly after waking), during the afternoon (at a convenient time) and during the evening (shortly before going to sleep). Three home blood pressure measurements, with a 1 minute interval between measurements, will be performed at each time each day (a total of nine blood pressure measurements each day). Participants will be provided with instructions regarding these measurements. The aim is to determine if reducing nitrate metabolism to nitrite (the precursor of NO) using antibacterial mouthwash will alter blood pressure. The antibacterial mouth wash can temporarily reduce the number of bacterial on the tongue that can reduce nitrate to nitrite. On the morning of day 4, at the end of each 3 day intervention period, (visit 2 and visit 3) participants will visit attend the School of Medicine and Pharmacology at the Royal Perth Hospital once for approximately 1.5 hours. Participants do not need to fast, but are asked to have the same breakfast meal prior to each visit. Prescribed medication will be taken as usual. At each of the two visits participants will: *Have a 15 ml fasting blood sample (approximately 3 teaspoons) taken to measure the metabolism of the nitrate, and to measure biochemical factors related to blood pressure. * Provide a 5 minute saliva sample. *Have the nitrate reduction by the bacteria in the mouth tested. This will involve holding a water and a nitrate solution in the mouth for 5 minutes each, before spitting them into a collection vessel. *Have arterial (blood vessel) stiffness measured using the CR2000 device. * Bring in the home blood pressure monitor for downloading of blood pressure measurements from the previous 3 days.