The Need for Chemical Compatibility Studies of Subcutaneous Medication Combinations Used in Palliative Care

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When a person with a life-limiting illness is unable to swallow, the subcutaneous route of administration is a widely used way of administering many medications, either as repeated bolus injections or by continuous infusions to complement transdermal, sublingual, or rectal routes of administration. To optimize symptom control as changes are made from other routes of administration to subcutaneous delivery, basic principles for ensuring optimal net clinical benefit (therapeutic benefit and minimizing side effects) must be understood as fully as science will allow. Despite the widespread use of combinations of injectable medications in this clinical setting and the availability of the technology to do the studies, the limited work done suggests that there may be significant drug loss with some combinations of medications without any visual or physical changes apparent. Work needs to be done urgently to evaluate a wide range of medication combinations used extensively in hospice and palliative care for chemical compatibility, while ensuring the work that has been done in other areas (anesthetics, chronic pain) is adopted into practice as results become available. Almost all of these medications are off-patent and there is therefore no financial incentive for the pharmaceutical industry to do the studies on medications now produced generically. Other sources of funding need to be identified. At best, it is likely that optimal symptom control is at times compromised in palliative care without chemical compatibility data for combinations of injectable medications and, at worst, toxicity is generated unknowingly.