Chemical preservatives may include:
(1) phenol
(2) formaldehyde
(3) benzyl alcohol
(4) parabens
(5) polyethylene glycol
(6) sodium sulfite
Consequences of injecting a drug that contains a preservative or particulate matter:
(1) inflammation (arachnoiditis, ventriculitis, aseptic meningitis)
(2) neurotoxicity
(3) neuropathy
It may be hard to be sure that the preservative is the cause of a patient's problems, so usually it is easier to avoid the preservative all together. A preservative can be implicated with some certainty if:
(1) The patient has a problem after use of a formulation that contains a preservative, but not after use of formulation without the preservative (requires multiple injections).
(2) The preservative is a known toxin (like formaldehyde.
(3) The concentration of the preservative is high, above levels known to be safe.
Recommendations:
(1) Use a preservative-free formulation if possible.
(2) If a preservative-free formulation is not available, then select a formulation with a level of a preservative unlikely to cause harm.
(3) Filter out any particulate matter.
Differential diagnosis:
(1) true meningitis caused by injecting a contaminated solution or lack of sterile technique
(2) toxicity due to the drug being injected
(3) toxicity due to chemical solutions used to clean the skin prior to the injection
