NEW YORK (Reuters) -- Nitrates, a class of drugs used to treat the crushing heart pain of angina, work better with one simple act -- taking a drink of water before placing the pill underneath the tongue.
The drugs, which decrease the oxygen requirement of the heart muscle, are also used during cardiac catheterization, a heart diagnostic procedure.
According to the first study of its kind, when patients undergoing cardiac catheterization wet their mouths before placing a nitrate pill underneath their tongue, there was a significant drop in blood pressure compared to those who did not wet their mouths. The significant drop suggests that the patients with wet mouth membranes absorbed more of the drug.
However, wetting the mouth did not have any effect on those given a spray form of the drug, according to the report in the September 1 issue of the American Journal of Cardiology.
"Dry mucous membranes, due to fasting for cardiac catheterization, after mouth breathing with exercise, or during the night, may further impair the absorption of sublingual [beneath the tongue] nitrates," wrote lead study author, Dr. Scott Kinlay, of the Cardiac Catheterization Laboratory at Brigham and Women's Hospital in Boston.
It is unclear why wetting the mouth can help the drug work more efficiently. But "water may improve the action of sublingual nitrate tablets by increasing the speed of dissolution of the tablet, especially when the mouth is dry," he said.
In contrast, "the spray preparation permits exposure of the full dose of nitrate to a greater surface area of absorption, and wetting the mucous membranes did not result in a statistically significant increased effect in this study," he wrote.
The researchers did not test to see if mouth wetting could help quicken the action of nitroglycerin, the type of nitrate most often used by angina sufferers to control the pain.
However, "the timing of the changes coincides with the relief from angina," Kinlay concluded.
SOURCE: The American Journal of Cardiology (1996;78:555-558)
