The US Food and Drug Administration (FDA) last week warned that differences in how drugmakers and compounders label the strength of injectable drugs may lead to dangerous dosing errors.
"Conventional manufacturers label their injectable products with the strength per total volume as the primary and prominent expression of strength on the label, whereas some compounders label their injectable products differently," FDA writes.
For small volume parenteral drugs and biologics, FDA recommends that strength per total volume be the primary and most prominent expression of strength, followed by strength per milliliter enclosed by parentheses.
According to FDA, two recent MedWatch reports cited medication errors that led to patients overdosing on compounded injectables that featured strength per milliliter more prominently on the labels than the strength per total volume.
In one case, a patient was accidentally administered 50 times the prescribed dose of fentanyl. In that case the IV bag containing the compounded drug was labeled 50 mcg/mL in large font with the strength per total volume (2,500 mcg/50 mL) underneath it in smaller print, which the MedWatch report cited as the cause of the error.
In another case, a patient was given up to 10 times their prescribed dose of ketamine due to a similar misinterpretation of the amount of ketamine in the IV bag.
In the case of the patient that was given too much ketamine, FDA says the patient was reported to be abnormally drowsy as a result of the error. The agency does not indicate what happened to the patient that was overdosed with fentanyl.
FDA also says it has received numerous complaints from healthcare practitioners warning that compounded products featuring strength per milliliter could lead to confusion and dosing mix-ups.
Such mix-ups could be avoided, FDA says, if compounders were to follow the same labeling conventions as traditional drugmakers, though FDA does not review the labels of compounded drugs before they are sold.
As such, FDA is advising healthcare professionals to be vigilant when administering compounded products to patients to ensure they do not misinterpret the amount of the drug present. FDA also says that physicians could request that compounders they purchase from label their injectable drugs in terms of strength per total volume.