A recent commentary in JAMA Dermatology highlights the problems associated with unpublished trials.
It looks at the case of imiquimod, widely considered beneficial for treating children with molluscum contagiosum (a viral infection that affects the skin). According to the commentary, 2 large randomised clinical trials have shown imiquimod is neither safe nor effective in these cases. However, neither trial has been published.
The author of the article predicts that prescriptions of imiquimod would decrease for molluscum contagiosum in children if the results of these trials were made available.