We are mixing our own and did the calculations to get the same concentration as we usually purchase. This works out to 0.01 ml of 1:1000 lidocaine per 1.0 ml of lidocaine. So, add 0.2 ml to a 20 ml vial, or 0.5 ml to a 50 ml vial. Since the solution is already buffered, we are not currently adding any bicarb. Also, since there is methylparaben as a preservative in the lidocaine and another type of preservative in the epinephrine MDV, I feel that with refrigeration, the shelf life should be at least 2 weeks... maybe 4. Don't mix more than you can use in a couple of weeks and be certain that sterile technique is adhered to for the mixing. The mix is the same whether the lidocaine is 1% or 2%. Sometimes you need to wait longer for the 1% to take full effect. The mixture needs to be stored in a dark, cool place. If it becomes discolored, it must be discarded.