Trimix as you may have realized is a Rx Formulary which has several variations on the mix of three ingredients which the Urologist prescribes. The prescription is in vial of usually 10 CC and is injected in the side of the penis shaft. Syringe is usually 1/2" 30 gauge,with initial dose of .15cc.
A powder form/fluid and mixed within inhector, is available yet not commonly prescribed and that is injected into the uretha.
To the best of my knowledge Trimix is taken via the urethra and not by injection with needle. Also, if it is the genuine product, it comes with a patient instruction sheet which you need to study.