They boost each other and block side effects? (In mice)
Rapamycin and metformin are viewed by many as the two most promising anti-aging drugs, but now scientists have found that these drugs can work hand in hand and show combined benefits, boosting each other’s effectiveness and blocking side effects — or at least that’s what we’ve seen in mice.
When tested by the Intervention Testing Program metformin failed to significantly increase lifespan in mice. However, in combination with rapamycin, it worked synergistically, leading to a drastic increase in median and maximal lifespan.