Lancing the finger and heel to obtain capillary blood for specimen collection and diagnostic testing is a painful and tissue damaging procedure. With each lance, there is direct splicing of capillaries along with free nerve endings resulting in an immediate localized pain response and hyperalgesia from the release of pain producing substances. Opioid agonists (morphine, fentanyl, loperamide) have demonstrated significant analgesia when locally injected or topically applied to a site of inflammation/injury in animal models.
Loperamide, a piperdine derivative with a structure similar to the synthetic opioid meperidine, has strong affinity for Mu opioid receptors. It was approved by the FDA in 1969 as an anti-diarrheal agent with Mu opioid activity mimicked the constipating effects of other opioids, but with markedly reduced CNS effects due to its affinity for p-glycoprotein, preventing crossing the blood brain barrier (BBB) under normal circumstances.
This prospective, double-blind, repeated measures, randomized investigational new drug trial used loperamide developed as a topical gel in 34 adult participants to determine its analgesic effects during repeat finger lancing. The investigators also assessed for any local skin reaction to the gel application and for any constipation or abdominal cramping which might be evidence of systemic absorption and Mu opioid agonist activity on the gut.
This study would be applicable for use in 28.9 million adults who are diabetic and require finger lancing for blood glucose monitoring and the high risk newborn population who require repeat heel lancing for specimen collection.
