Trimix needs to be kept in the freezer and therefore must be thawed out prior to each use. Trimix does not require freezing nor refrigeration. Trimix contains 3 agents: prostaglandin, papavorin and phentolamine. Caverject contains only prostaglandin. Both are injected into the same area at the base of the penis away from the urethra and the main nerve on top of the penis.