Influence of purinoceptor antagonism on diadenosine pentaphosphate-induced hypotension in anesthetized rats.

Diadenosine polyphosphates (ApnA; n = 3-6) are potent vasoactive agents in isolated vessels. Information on effects of ApnA in vivo is still limited despite the fact that these compounds are starting to be used in humans. This study was designed to compare the effects of ApnA and their possible metabolites on blood pressure in vivo and to functionally identify purinoceptors involved in their action. All four ApnA and their degradation products induced a sustained drop of mean arterial blood pressure during i.v. infusion, which was fully reversible. The rank order of potency was Ap4A > or = Ap6A > Ap5A = Ap3A = ATP = ADP > AMP > or = adenosine, suggesting that the hypotensive effect is predominantly evoked by the original dinucleotides and not by their degradation products. The hypotensive effect of Ap5A was reduced by the P2X and P2Y(1) purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, the A(1) purinoceptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, and the A(2) purinoceptor antagonist 3, 7-dimethyl-1-propargylxanthine. The hypertensive effect by the prototype P2X receptor agonist alphabeta-methylene ATP was inhibited by pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, too. Purinoceptor antagonists reduced the maximal effects of the agonists indicating a noncompetitive inhibition. In summary, the reported vasocontractile effect of ApnA seems to be limited to isolated preparations under resting tone conditions; however, the systemic cardiovascular effects of all four ApnA are hypotensive, also making them candidates for blood pressure reduction in humans. These effects are fast in onset and easily reversible. Activation of different purinoceptors in the vasculature (most probably P2Y(1) and A(2) receptors) contributes to the Ap5A-induced decrease of mean arterial blood pressure.

Availability of antibiotics as over-the-counter drugs in pharmacies: a threat to public health in Vietnam.

A survey on the use of antibiotics purchased through retail pharmacies was conducted in the Badinh district of Hanoi, Vietnam. The survey found that purchasers visit a pharmacy when they or those who felt they needed antibiotics had minor symptoms such as cough (34.1%), sore throat (32.5%), stomach upsets (10.0%) and diarrhoea (8.8%). The most often purchased antibiotics were ampicillin (31.1%), amoxyllin (16.7%), cotrimoxazol (11.6%), tetracycline (5.2%) and cephalexin (4.8%). The median of the purchased quantity was 10 tablets, the mean 11.34 tablets (95%CI 9.65-12.97). About 30% of the purchasers intended to take antibiotics for three days or less. The mean cost of a antibiotic purchase was US$1.27 (95%CI 1.06-1.39). The main reason for not taking a full course of antibiotics was not economic constraint, but the purchasers' poor knowledge about antibiotics. Logistic regression analysis indicates that age of purchasers, length of symptoms and kinds of treatment used before visiting a pharmacy could be used as predictive variables for the decision to buy antibiotics in preference to alternative drugs. Antibiotics are used when illness lasts longer than one week and antibiotics have not yet been taken. Antibiotics are also purchased by young rather than old people. The study documents the need for better health education about the rational use of antibiotics in the general public.