Debating the evidence : oral contraceptives containing drospirenone and risk of blood clots

Skepticism is an essential quality in science. We doubt, re-examine and demand the highest quality of evidence. However, sometimes this puts us in an awkward situation. How much evidence do we need before we act? This dilemma is a constant problem in drug safety. Treatment decisions are always a balance of risks and benefits and there may be a paucity of evidence about rare or very rare adverse events.