I think what you are asking is if you can continue to use your drawing needle for drawing subsequent shots, and just change to a new shooting needle for each shot and discard that one, but re-use the drawing needle next shot. Still, bad idea. It is no longer sterile! Pins are too cheap to worry about wasting a few. What's the big deal about using two needles per injection? Look... here's what I do. I buy 3cc syringes equipped with 21ga 1-1/2" pins, in boxes of 100. I buy 25ga and 23ga needles, 1-1/2" long, in boxes of 100. I don't even remember what I pay... less than $20 for the rigs... I think Terumos work out about 16 cents each. The pins are really cheap... about 6 cents each as I recall figuring out one day. So small that I don't even notice the price. I draw with the 21ga already on the rig, then change to either 23 or 25ga for the shot. I discard both pins in my approved, labeled sharps container, and toss the syringe and wrappers and caps in the trash. The front section of my morning newspaper costs me more than my injection equipment. An abscess would cost me a lot more.

Do the right thing. DO NOT re-use pins for any purpose! It is the wrong thing to do.