Washington, November 7 : The conventional blood pressure medicines may be replaced by a hypertension vaccine, if the results form a small study testing the safety and tolerability of the vaccine are replicated in further research.

“Despite the fact that effective drugs are available, only about one out of four people has their blood pressure successfully controlled,” said Dr. Juerg Nussberger, professor of medicine at the University Hospital of the Canton of Vaud, in Lausanne, Switzerland.

“Many patients are apparently unable or unwilling to take pills every day for the rest of their lives. If we could add or substitute a vaccine that would need to be given just every few months, I think we could achieve better control of high blood pressure,” added Dr. Nussberger, who is also the lead author of the study reported at the American Heart Association’s Scientific Sessions 2007.

The vaccine works by reducing the production of angiotensin II, a molecule that constricts blood vessels and raises blood pressure, which is already the indirect target of several blood pressure medications.

During the study, 72 patients with mild-to-moderate high blood pressure were injected with either 100 or 300 micrograms of the vaccine or a placebo. The patients included 65 men and seven women, average age 51.5 years old.

After injections at zero, four and 12 weeks from the start of the study, patients who were administered the vaccine showed a strong antibody response against angiotensin II, which was significantly higher in those receiving the higher dose. Blood pressure changes were evaluated at week 14.

Among patients who were administered the vaccine, daytime systolic blood pressure (the top number of a blood pressure reading, measuring pressure as the heart constricts) reduced significantly by 5.6 millimetres of mercury, and diastolic blood pressure (the bottom number of a blood pressure reading, measuring pressure as the heart rests between beats) decreased by 2.8 millimetres of mercury.

“Quite unexpectedly, our vaccine had the most striking effect early in the morning, the most dangerous time to have high blood pressure because it raises the risk of heart attack and stroke,” said Dr. Martin Bachmann, senior co-author of the study.

“Antibodies produced by the vaccine seem to function like a sponge. The sponge empties out during the night when little angiotensin II is produced, so it is able to take up all the angiotensin II produced early in the morning,” Bachmann added.

As compared to ACE inhibitors and ARBs, the vaccine induces only a low increase in renin, an enzyme that is thought to cause inflammation and is implicated in kidney failure.

Dr. Buchmann has revealed that the next step in developing the vaccine is another small trial to determine whether a different injection regimen will create a larger antibody response and a greater reduction in blood pressure. (ANI)