Sebastian Coe insists athletics chiefs will intensify the war against drug cheats in the aftermath of the positive tests for Asafa Powell and Tyson Gay.
America's Gay, the fastest man in the world this year, and Jamaica's former world record holder Powell have both tested positive for banned substances.
It is not known which substance Gay took, although that should be confirmed after his B sample is analysed.
Powell, who has run 9.88secs this year but failed to make the Jamaican team for next month's Moscow world championships, was tested at the national trials in June and returned an adverse finding for oxilofrine - a stimulant that boosts fat-burning.
Jamaica's Sherone Simpson, a three-time Olympic medallist, also tested positive.
Coe, vice-president of the International Association of Athletics Federations (IAAF) and chairman of the British Olympic Association, is determined to clamp down on doping.
"The most important thing for me is that the testing system is working and, for the sake of clean athletes, it is very important we do not flinch in our efforts," he said.
"This is not a war we can afford to lose, and it is important for any athlete to know that if they want to risk cheating, that they are going to get caught.
"We are still waiting for the B samples ... But the message is getting through and we are not taking our foot off the pedal."