During the 1980's, imports of coca by Stepan have ranged from 56 metric tons to 588 metric tons a year, according to figures from the Drug Enforcement Administration.

Some coca cultivation is still permitted in Peru, where coca leaves have been both chewed and brewed into teas for centuries. However, the United States has been pressuring Peru and other countries to eradicate the plant and substitute other crops.

Mr. Donaldson declined to discuss whether the Reagan Administration's planned attempt to reduce South American coca growing could have an impact on the company and the formula used to make its soft drink.

He also declined to say whether the new formula Coca-Cola introduced in 1985 contained a coca derivative, noting that it was company policy not to discuss its product formulas. The Coca Eradication Plan

American officials said recently that, as part of the Administration's war on drugs, they planned to begin testing a coca eradication program in Peru within 90 days. The testing, which is contingent on final approval by the Peruvian Government, would involve the aerial spraying of powerful herbicides.

Critics of the herbicide project charge that it is politically motivated - an attempt to convey an impression of bold action in an election year - and environmentally hazardous.

Others argue that it is bound to fail. According to estimates based on D.E.A. data, enough coca to satisfy the United States demand for cocaine can be produced on 96 square miles of land - an area smaller than the borough of Queens. The climates of much of Latin America as well as Africa and Asia are suitable for the cultivation of coca, a hardy, woody shrub. How the Coca Is Acquired