08/06/2026
DILUENTS FOR BOTULINUM TOXIN: ON-LABEL VS OFF-LABEL CONSIDERATIONS
When discussing botulinum toxin, we often focus on dosing and technique, but the choice of diluent also has important clinical, regulatory and medico-legal implications.
In the UK, preservative-free 0.9% sodium chloride is the manufacturer-approved diluent specified within botulinum toxin licences, making it the on-label choice for reconstitution.
Some practitioners choose to use bacteriostatic saline, which contains benzyl alcohol. Proposed benefits include reduced injection discomfort and the presence of a preservative that may support clinic review protocols and potential top-up appointments.
A key distinction often overlooked is that “off-label” and “unlicensed” are not the same thing. Off-label use refers to using a licensed medicine outside the terms of its licence, whereas an unlicensed medicine does not hold a UK marketing authorisation.
Some bacteriostatic saline products used in UK aesthetic practice may be supplied as unlicensed medicines and are therefore subject to the Human Medicines Regulations 2012. Under Regulation 167, unlicensed medicines (“specials”) are generally supplied to meet the special clinical needs of an individual patient, rather than for routine stock use.
The use of off-label and unlicensed medicines is not prohibited when there is a clear clinical rationale and it is in the patient’s best interests. However, this places greater responsibility on the prescriber.
Best practice includes:
• Having a clear clinical justification
• Informing the patient of the rationale
• Obtaining informed consent
• Documenting discussions and decision-making appropriately
Good aesthetic practice is about more than outcomes—it’s also about governance, transparency and defensible prescribing.
