Compatibility and Stability

The National Coordinating Committee on Large Volume Parenterals (NCCLVP) defines instability as "a phenomenon which occurs when an LVP or LVP drug product (IV admixture) is modified due to storage conditions (e.g. time, light, temperature, sorption)." An unsuitable product may be formed.

Incompatibility is defined as "a phenomenon which occurs when on drug is mixed with others and produces an unsuitable product by some physiochemical means." The new product is unsuitable for administration because the "active" drug has been modified (e.g., increase in toxicity), or because some physical change (e.g., solubility) has occurred.

If the instability or incompatibility of a given preparation is not known, the pharmacist should consider the factors listed in this section to anticipate the likelihood of these problems.

The pharmacist may use the following suggestions to minimize incompatibilitites and instability:

1. Use only freshly prepared solutions.
2. Follow an established order of mixing, and mix the preparation thoroughly after adding each ingredient.
3. Do not shake preparations vigorously unless indicated in the labeling. Rotate or swirl preparations to minimize foaming and the formation of air bubbles.
4. Use as few additives as possible.
5. Dilute any problem additive.
6. Develop an incompatibility table or file for frequently compounded preparations.
7. If the preparation is to be filtered, ensure that any removed particulate matter is not the active drug.

If an incompatibility cannot be corrected or prevented, consider the following administration techniques:

• Administer the preparations separately at staggered times.
• Flush the administration line or set between preparation administrations, and use normal saline, not heparin.
• Use an alternative site of administration.