Allergan (makers of Botox) specifically recommend using unpreserved saline (0.9% NaCl) which was used during the clinical trials on Botox and how the FDA approved its use.
Botox was approved for use when reconstituted with non-preserved saline. Having said that, many people use preserved saline for patient comfort.
I prefer to use preserved saline for reconstitution because it is slightly more comfortable for the patient but the FDA trials were done with unpreserved saline but there is no difference in duration of effect either way or onset of action.
I have not found that it matters. As my colleagues have pointed out, preserved saline is more comfortable than non-preserved. The package insert reflects the conditions used for initial studies of Botox.
Stephen Weber MD, FACS
Denver Facial Plastic Surgeon
The Allergan FDA clinical trials reconstituted "Botox" (onabotulinum) with non-preserved saline, but most injectors now use preserved saline as it has a mild anesthetic effect. This allows for more comfortable injections with no loss in efficacy.
It is recommend to mix with unpreserved saline, but it hurts more so I use presevered as well -- it is less painful and has no change in the clinical result. Best, Dr. Emer.
While it is recommended to use unpreserved saline, I use preserved saline because it does not hurt as much.
Botox comes as a fine powder. The doctor adds sterile saline to turn the medication into a liquid for treatment. The official FDA approved method is to used non-preserved saline this is based on evidence from studies performed with laboratory animals.. However, many very experienced physicians use preserved saline. The advantage is that preserved saline makes the injection more comfortable and has been proven, in many well done studies, to be just as safe and effective as non-preserved saline in treating humans.
I am surprised that you are asking this question because not one patient has ever asked me about this before, but....
Although Allergan recommends using non-preserved saline for reconstitution, the overwhelming number of providers will use preserved saline because the injections hurt less.