The days of pills and injections may one day be a troublesome memory. Recent advances in transdermal drug technology -- in which drugs enter the skin directly through patches -- are convincing researchers that tablets and syringes may go the way of leeches in medical care.

"Transdermal medication is the frontier of the pharmaceutical industry," said Yie W. Chien, director of the Controlled Drug Delivery Research Center at Rutgers University. "Skin patches are already used for heart ailments and other diseases. We are now developing patches that can deliver drugs at a controlled, therapeutically effective rate for angina, hypertension, diabetes and contraception."

Everyone has a physiological clock. Ideally, drugs should be administered to fit that timetable. Some medications, for example, are more effective if they are delivered to the bloodstream in the morning. Others, such as insulin, are best applied after meals when the glucose level is high.

Contraceptive patches would be among the most eagerly awaited acheivements in the industry.

"A woman would wear it for a week, replace it with another patch and then repeat that procedure continuously," said Chien.

The patch, which would be smaller than the average Band-Aid, would hold varying amounts of medication -- including the hormones estrogen and progestin -- depending on the woman's normal physiological cycle from week to week.

Patches can work while the wearer is swimming or bathing. Unlike oral medication, the medicine cannot be broken down by stomach acids and liver enzymes.

Research is focusing on the timing of drug delivery and proper dose regulation from the patches. While pharmacists are convinced that the patches will have a place in the medical system of tomorrow, they are not certain how soon tomorrow will come.