It is recognized that many experimental compounds used in research may need to be diluted or combined for use in laboratory animal research. This Policy details ARC requirements for handling, use, and storage of fluids[1] and diluted drugs[2] that are intended for use in research animals at UCLA. Refer to the ARC Policy on Use of Pharmaceutical-Grade Compounds for expectations governing the use of medications, anesthetics, analgesics, euthanasia agents, and experimental agents, and the ARC Policy on Expired Medical Materials for further information on the use of expired drugs and medical materials in survival and non-survival procedures.


All substances used in animals must be listed in the approved ARC protocol, unless treatment is prescribed and directed by the DLAM veterinary staff. Furthermore, administration of combinations of drugs must also be described in the approved ARC protocol since there is a potential for unexpected and potentially toxic effects. When dilution of a pharmaceutical grade drug solution is necessary, it must be done using aseptic technique and the final product must be properly labeled and stored. Similarly, when preparing drug solutions for injection from solid material, the final solution for injection must be filter-sterilized. When multiple injections will be made from the same solution, the solution must be appropriately stored in sterile re-sealable septum-capped vials. In most cases, open-mouthed containers such as Eppendorf or centrifuge tubes must not be used as containers from which multiple injections are made, as the lack of a rubber stopper does not permit sterile entry of the needle into these types of containers. Exceptions are noted below.

Additional Guidance

Choose a dilution scheme that will result in a dosing volume that makes sense for your studies – neither too large a volume for the injection route into the animal, nor too small a volume for accurate dilution and delivery. This can be particularly important for anesthetics and analgesics. To avoid waste and contamination potential, only make up what is needed.

  1. All drugs requiring dilution must be diluted and maintained using sterile technique.
    1. Use sterile saline or sterile water as the diluent unless otherwise documented in your approved animal protocol.
    2. When diluting a pharmaceutical grade drug solution from a septum-capped vial, sterile needles and syringes must be used to transfer drug solution and diluent into sterile empty vials (see image below). These vials are available from the DLAM Pharmacy,, in both clear and amber glass, or may be purchased from any UCLA-approved vendor. Use a size appropriate for the volume of liquid.
      Sterile Empty Vial
    3. An exception to (b) would be if greater accuracy is required and/or if serial dilution is necessary, in which case dilutions may be made using sterile pipettes and pipettes and tubes under sterile conditions (i.e., in a tissue-culture hood), with the final solution being made into a sterile septum-capped vial.
      Eppendorf and centrifuge tube
    4. When making solutions and subsequent dilutions from solid drug material or when dilutions are made from non-pharmaceutical grade drug solutions, regular pipettes and tubes may be used, but the final solution for injection must be filter sterilized into a sterile septum-capped container.
      1. An exception to the requirement for use of a septum-capped container in such cases is when it is necessary to make multiple small-volume microinjections from a limited volume stock, over a short period of time (a few hours), and/or if blunt cannula injections are required. In such cases, smaller regular-capped sterile tubes may be used but care must be taken to reduce the chances of introducing contaminants by using new, sterile needles between injections.
      2. Another strategy would be to draw up the injectate into the dosing syringe in a sterile tissue-culture hood in the lab space; this syringe becomes both the sterile storage vial and the method for dosing. Change sterile needles with each animal injected.
  2. All diluted drugs must be labeled with the following information:
    1. Drug name
    2. Name of person who made the dilution
    3. Drug concentration
    4. Expiration date (see #4, below)
    5. Any additional information required by other entities, such as the DEA or ARC protocol
  3. Practice aseptic technique with the multi-use vial to maintain sterility.
    1. Multi-use vials must be disinfected prior to each use by swabbing the rubber stopper with alcohol.
      vial stopper swab alcohol
    2. A new, sterile, clean needle must be used when entering through the stopper into the multi-use vial.
  4. If handled as described above, diluted drugs expire 30 days from dilution or on the expiration date of the original drug if that is earlier than 30 days from dilution. A 30-day expiration date minimizes the likelihood of contamination while allowing for compound stability. If the solution turns cloudy or discolored or becomes ineffective, it must be discarded prior to the expiration date. If a lab has a method for validating efficacy of a drug or particular cocktail beyond the 30-day standard, or published data regarding stability is available, they can request an exception from the ARC, citing this justification..
  5. If handled as described above, multi-use fluid bags or vials (such as 0.9% saline) used for subcutaneous fluid administration or drug dilution must be discarded within 30 days to minimize the risk of contamination due to multiple needle entries into the stock bag or vial. The open date or expiration date must be written on the vial or bag to ensure that the container is discarded within 30 days. If a lab has a method for demonstrating sterility beyond the 30-day standard, they can request an exception from the ARC, citing this justification.
  6. If handled as described above, stock solutions that are divided into aliquots, but are not diluted, expire at the same time as the original stock solution. The expiration date must be written on the aliquot.
  7. Drugs should be stored according to special requirements (e.g., amber bottles for light-sensitive drugs such as carprofen). Refer to packaging provided with the original stock container or information on the manufacturer’s website. At any time, if the user notices any cloudiness or bacterial / fungal growth inside the vial, it must be discarded immediately.


  1. Fluids: for the purpose of this Policy, supplemental 0.9% (isotonic) sterile saline or lactated Ringers solution that is provided to an animal as a replacement or support for lost body fluid, either through blood loss or by dehydration, or as a preventative for perceived loss during surgery.
  2. Diluted drugs: for the purpose of this Policy, a solution of a compound removed from a stock bottle with a high concentration, and placed in a secondary container with a diluent, to achieve a lower concentration of the compound.


Assessment of Sterility in Fluid Bags Maintained for Chronic Use
Authors: Matthews, Kristin A; Taylor, Douglas K
Source: Journal of the American Association for Laboratory Animal Science, Volume 50, Number 5, September 2011, pp. 708-712(5)

Beyond-Use Dating of Extemporaneously Compounded Ketamine, Acepromazine, and Xylazine: Safety, Stability, and Efficacy over Time
Authors: J Taylor, Brett; Orr, Steven; Chapman, Jennifer; Fisher, Diana
Source: Journal of the American Association for Laboratory Animal Science, Volume 48, Number 6, November 2009, pp. 718-726(9)

Website: Veterinary Information Network

Drug Dilution & Storage Guidelines, University of Maryland Baltimore Animal Care and Use Program. Accessed 04.2023.

Guidelines for Use of Anesthetic Mixtures and Diluted Drugs in Laboratory Animals, UC Davis IACUC. Accessed 04.2023

Drug Dilution and Storage Guidelines, University of Toledo IACUC. Accessed 04.2023

Proper Preparation, Dilution, Usage and Storage of Drugs, Medical Materials and Controlled Substances, University of Rochester Medical Center, University Committee on Animal Resources. Accessed 04.2023.

Approved 3/27/23