I’ve been wondering - are the trials TRULY rando

I’ve been wondering - are the trials TRULY randomized or do the researchers ensure that for every 2 patients that receive the drug, 1 receives placebo. The reason I ask is that if you do an interim analysis of 51 patients where the treatments are TRULY randomized, you could end up with 30 placebo patients and only 21 L. patients, or 51 patients who have all received L., or a myriad of other combinations. Anyone have insight or knowledge?