Injecting - Increase effectiveness of IM Diazepam

[delphinen]

SWIM has many Diazepam ampoules of 10mg each one. He usually inject in the arms and very often in the buttocks and legs.

At first the feeling of relaxing was incredible, injecting under the shower felt godlike, but tolerance grew incredible fast and SWIM has to inject 3 ampoules to get the same relax now, he also tried and ampoule of 3mg Lorazepam which found nothing special, so:

SWIM was wondering if there is a particular muscle, particular syringe, or some form to increase the potence of genuine IM Diazepam.

Thanks in advance.