Today the White House, tomorrow the world for Nancy Reagan's highly successful crusade to draw attention to drug abuse.

First up on her expanded agenda will be an April 23 White House briefing for the first ladies of 27 foreign countries she is inviting to Washington, many of whom have expressed an interest in her efforts to curb the use of illegal drugs. The next day Mrs. Reagan will fly with them to an international drug abuse conference in Atlanta sponsored by Parent Resources and Information on Drug Education (PRIDE).

It's all part of Mrs. Reagan's efforts to "internationalize" the high-visibility media approach she's used to try to get America to kick the drug habit. Depending upon President Reagan's post-economic summit travel plans, there is some thought that the first lady could take off from Bonn on her own to view anti-drug work in several European cities, maybe even making a couple of speeches.

Calling it an "evolution" rather than a restructuring of her program, the first lady's press secretary, Sheila Tate, says that Mrs. Reagan has built "such a credible base that she could do anything in this field. That's why it's entirely appropriate to reach out to other first ladies."

Mrs. Reagan also will concentrate on the cost to society of drug abuse. There are plans for her to visit a jail and to try to focus on attendant problems of users, such as babies born addicted to heroin, child abuse and drugs in the work place.

"She's done so much in this country to raise drug abuse on the social agenda that the media is paying more attention to it and people are more sensitive to the scope of the problem. In order to reinforce that she has to keep building on it," says Tate. "I think she succeeded even beyond her own expectations of what she could do."

Though there may be other trips abroad -- some even to the source of illicit drug trade in Asia and South America -- Mrs. Reagan has no plans to pitch for stepped-up enforcement on behalf of her husband to foreign leaders.

"The president is very proud of what she's doing," says Tate, adding, "It tickles him."