Naloxone for the Treatment of Opioid-Induced Pruritus

Hypothesis: Naloxone co-administered simultaneously with standard Patient Controlled Analgesia (PCA) basal and bolus morphine will significantly reduce the incidence of Opioid Induced Pruritus (OIP) without affecting analgesia or opioid consumption in children.

Specific Objectives:

• To determine if naloxone (12 µg/ml) mixed in a single infusion with morphine (1 mg/ml) will be effective in the prevention of opioid induced pruritus (OIP).
• To determine if treatment with naloxone will result in attenuation of analgesia or an increase in opioid utilisation.
• To determine if treatment with naloxone will reduce other opioid induced side effects such as nausea and vomiting.

Methods: This study is divided into two phases. Phase 1 - Although, there are studies confirming the compatibility of morphine (4 mg/mL) with naloxone (16 µg/mL) in separate infusion pumps run into the same intravenous site, there are no studies confirming the chemical and physical compatibility of morphine and naloxone in the same syringe with the standard concentrations used at BCCH. Therefore, a compatibility and stability study of naloxone and morphine solution in the same syringe will be performed.

Phase 2 - Phase 2 is a blinded clinical trial where 70 subjects will be randomized to receive either morphine mixed with naloxone or morphine mixed with placebo.With institutional review board approval, and written parental/guardian informed consent (and assent if appropriate), we will recruit children, ages 5-16 years, receiving intravenous opioids via PCA for post-operative pain control. Subjects will be evaluated every 4 hr for pain scores, frequency of vomiting, nausea, pruritus, sedation, and respiratory depression. At 24 and 48 hr, the total morphine consumption will be calculated.

Data analysis: Differences in the incidence and intensity of pruritus between the two groups will be compared. We will review side effects using the following control variables: (1) demographic data; and (2) summation of opioid use in each 4 hr period for total opioid consumption. ANOVA and crosstabs will be used where appropriate to analyze data.

Inclusion criteria

• Children 5-18 years of age undergoing surgery at BCCH
• ASA I - II.
• Children receiving PCA morphine.
• Informed consent/assent provided by child/parent/guardian.

Exclusion criteria

• Children with known abnormal developmental profile.
• Children with known opioid allergy.
• Inability/failure to obtain informed consent/assent from parent/guardian/child.
• Children receiving concurrent opioids.
• Children with pre-existing pruritus from non-opioid related cause.
• Children receiving PCA hydromorphone or fentanyl.
• ASA 3 and above.
• Children who require admission to the Pediatric Intensive Care Unit (PICU). - Children involved in any investigational drug trial within the previous one month.
• Any child in the study that experiences unmanageable pruritus within the protocol time frame and is converted to hydromorphone will continue to be monitored for 48 hours. However, this will be taken into account during statistical analysis of study results. Appropriate conventional rescue medication for pruritus (diphenhydramine 0.5mg/kg IV 4hrly PRN) will be provided for any child who continues to experience pruritus.