Conditions: Pain
Keywords: Post-surgical pain Pharmacokinetics
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 50
Healthy volunteers: yes

Brief summary:
Morphine is the opioid used to treat pain after surgery. Acetaminophen (called APAP) can reduce the amount of opioids needed for this.

The problem is that morphine slows down digestion. That can delay pain relief from APAP pills. It can even change what the body does to the drug \[pharmacokinetics (PK)\].

Some doctors have started using intravenous (IV) APAP with morphine, instead of the pills.

This study will measure the PK of APAP pills and IV when used with morphine in healthy volunteers.

IV APAP will likely be more effective and cause fewer side effects when used with morphine to treat pain after surgery.

Detailed description:
Acetaminophen can significantly reduce the use of opioid analgesics when both are used concomitantly for treating moderate to severe pain. The use of IV acetaminophen used concomitantly with opioids has increased in practice for postsurgical pain relief over orally administered acetaminophen because it provides an immediate peak plasma concentration and is believed to provide a faster analgesic effect. Opioids used to treat pain inhibit gastrointestinal motility, including delaying gastric emptying. In patients receiving opioids the absorption of orally administered acetaminophen may be delayed and could result in gastric accumulation of acetaminophen thereby markedly changing the pharmacokinetic profile. The opioid-induced inhibition of gastrointestinal motility would not be expected to affect IV acetaminophen pharmacokinetics. Thus coadministered IV acetaminophen with opioid would yield better outcome in efficacy and reduced risk of side effects comparing with coadministration of oral acetaminophen and opioids.

Arms:
arm 1: Treatment A = 4 repeat doses of 1,000 mg oral acetaminophen (2 x 500 mg tablets) and an IV infusion of saline every 6 hours (Hours -6, 0, 6, and 12), and 2 infusions of intravenous (IV) morphine (0.125 mg/kg) at Hours 0 and 6 arm 2: Treatment B = 4 repeat doses of IV acetaminophen (1,000 mg/100 mL) and 2 placebo tablets every 6 hours (Hours -6, 0, 6, and 12), and 2 infusions of IV morphine (0.125 mg/kg) at Hours 0 and 6.

Interventions: intervention 1: Oral Acetaminophen intervention 2: IV Acetaminophen intervention 3: IV Morphine intervention 4: Placebo Tablets intervention 5: Saline
Intervention descriptions: intervention 1: Acetaminophen for oral administration (2 tablets, 500 mg/tablet) intervention 2: Acetaminophen for intravenous (IV) administration (1,000 mg/100 mL) intervention 3: Morphine for IV administration (0.125 mg/kg) intervention 4: Placebo tablets matching oral acetaminophen intervention 5: Saline placebo matching IV acetaminophen

Protocol document: