It's "first-year-in-review" time, and the Reagan administration has been taking it on the chin from the Heritage Foundation, Ralph Nader and other groups in between. The latest is Nader's Health Research Group, which yesterday detailed a drop in the Food and Drug Administration's enforcement efforts in 1981.

The study, based on the agency's weekly "Enforcement Report," found that there were 577 enforcement actions last year, compared with an average of 1,041 a year from 1977 to 1980, a 45 percent decrease. Product seizures dropped 65 percent, food enforcement activities dropped 47 percent and drug enforcement actions dropped 54 percent. "If 1981 is any indication, the Reagan administration is well on its way to bringing back adulterated foods and unsafe or unproven drugs and medical devices as a result of its promise to get government off the backs of industry," the group charged.

FDA spokesman Wayne Pines said the agency had not reviewed the group's study. But he conceded that during 1981 FDA enforcement actions did show a decline. "We haven't done an analysis as to why they are down. FDA has fewer employes than it did a year ago because of budget cuts, but we haven't done an analysis to find out if that is the reason."