Tolazoline is a drug that affects the muscles that control the compression of the blood vessels. Its primary use is to treat high blood pressure in newborn babies, but tolazoline is not available in North American markets, for this use or for others, as of 2012. Possible side effects of the drug in babies includes a sudden drop in blood pressure, hemorrhage in the intestinal tract and kidney failure, which means that babies receiving this treatment require professional supervision and monitoring of vital signs.
Blood vessels carry blood around the body because their walls are made from flexible material. The muscles surrounding the hollow interior of the vessels can contract and expand, in order to speed up or slow down the rate at which the blood moves through the vessels. This is partly intrinsically necessary as the heart pumps blood through in beats, making the movement of the blood vary in volume. Tolazoline affects the muscle that alters the interior diameter of the vessels outward, thus reducing the blood pressure.
The drug appears to only produce a useful effect in this way in newborn babies, and not in adults. Specifically, it works on the artery in the lungs, called the pulmonary artery, and so is used to treat persistent pulmonary hypertension in newborns, which describes a condition where the artery coming from the lungs sends blood into the body at too high a pressure. In addition, tolazoline is not suitable for all conditions of this kind in babies, but only in those children for whom other methods of altering blood pressure like ventilation and extra oxygen have not worked.
Restrictions like this for the use of tolazoline stem from the fact that the drug can produce some serious side effects. Sometimes the blood pressure can drop past safe levels into dangerously low levels. It can also cause ulcers in the baby's stomach and produce bleeding in the intestinal system. The child's kidneys may fail or the platelets in the blood, which are essential for normal blood clotting, may become reduced in number.
Commonly, the method in which tolazoline is administered to babies is through an infusion into a vein, such as a vein in the scalp. Babies may also receive antacid treatment beforehand to reduce the chance of ulcers and bleeding developing. A typical dose for a child is from 1 mg to 2 mg per kilogram of body weight as an initial dose; the dosage may be topped up every hour or so after this with a smaller dose.
