Ill snakes often require medications as part of their road to recovery.  Many drugs do not work well if given by mouth, and some drugs cannot be given by mouth. In these cases, intramuscular (IM) injections are required.  

The muscles on either side of the snake's backbone (spine) is the best location to give intramuscular injections.  Press down on the center of the back. The hard projection you feel is a part of the spine. Now gently roll your finer to either side. The soft tissue you feel is muscle.
It helps to hold a section of snake securely in one hand to reduce the snake's ability to wriggle while you are giving the injection. After feeling for the location of the muscle, aim your syringe at a 45 degree angle, and insert the needle beneath a scale and into the muscle.  You do not have to go very deep, usually about 1/2 the length of the needle is sufficient.  Pull back on the syringe slightly to ensure that no blood or fluid is present where you have inserted the needle.  If you aspirate fluid remove your needle from the area and try again at a different position.  If nothing is seen when you draw back, you should give the injection.  Switching from side to side between injections will help prevent excessive soreness from repeated injections in the same place.  A little bit of patience and slow gradual movements will result in successful IM injection experiences.