A simple and inexpensive packet of sugar and salts that may be administered as a home remedy could save the lives of tens of thousands of infants throughout the world each year, according to spokesmen for international child health agencies.

The technique, called Oral Rehydration Therapy, which has been in limited use in parts of Asia, Africa, India, Indonesia and South and Central America, was only recently made available in the United States.

The pre-measured mixture, dissolved in water, can be administered orally to the child or infant to restore the essentual fluids and electrolytes which are lost during bouts of diarrhea. Previously, only intravenous therapy in a hospital could provide adequate treatment for a dehydrated baby.

Electrolyte imbalance and fluid loss are the major causes of death and disability from diarrhea, which causes an estimated one-third to one-half of 17 million infant and children deaths in the world each year.

The mixture was found to be effective during a cholera epidemic in India in the early 1970s. Although it was cited by the British medical journal Lancet as "potentially the most important medical advance this century," it has been slow to reach more than a fraction of the estimated 500 million children worldwide who suffer from diarrhea caused by diseases like cholera or a host of microbes, parasites and viruses.

In countries like the United States, the problem is less critical because hospitalization and equipment for intravenous therapy is readily available.

But the World Health Organization and the United Nations Children's Emergency Fund are expected to launch a major drive later this year to make the packets of dehydration treatment as ubiquitous "as a pack of matches" all over the world, according to UNICEF executive director James P. Grant.

"You can bet," Grant said, "if this were a cure for cancer it would have gotten to every part of the world instantaneously. But it's not only something for children, it's something for poor children."

The packets prepared by the World Health Organization are inexpensive, amounting to less than 1 percent the cost of hospital treatment.

Even when the packets are unavailable, researchers have found that a home mixture of sugar and salt is about 80 percent as effective in an emergency. Leaflets distributed in Zimbabwe suggest that six capfuls of sugar and a half capful of salt be added to a liter of water.

In the United States, the mixture is manufactured by the Pennwalt Corp. It went on sale in pharmacies in mid-September as "Infalyte." Advertised to physicians rather than to consumers directly, according to a company spokesman, it sells for $1 a packet wholesale.

Its usefulness for better nourished children in developed countries was established in a study published this spring in the New England Journal of Medicine.

The study was conducted over a four-year period ended in March, 1981, with 52 children in four hospitals--three in Baltimore and one in New Orleans--and, for five months, with an additional 94 youngsters in a Panama City Hospital. The children ranged in age from three months to two years and had been hospitalized with acute diarrhea.

Among the team conducting the study was Dr. R. Bradley Sack of the Johns Hopkins University Medical School. A member of a World Health Organization task force on oral therapy, he helped establish the exact mix of glucose, sodium chloride, sodium bicarbonate and potassium chloride.