Page 94 - Journal of Special Operations Medicine - Winter 2015

Edward Scott Vokoun, MD

thank SGM Bowling for his interest in my article. with lower bioavailability and wider variability in effect
I One of the advantages of intravenous (IV) acetamino- among patients compared with oral formulations due
phen (Orfirmev ; Mallinckrodt Pharmaceuticals, www to the possibility of obtaining a subtherapeutic plasma
®
.ofirmev.com) is the ability to reach peak plasma con- concentration. 1
centration and thus meaningful pain relief within 15
1
minutes of infusion. No other route of administration Theoretically, the intramuscular (IM) route would be
will result in a pharmacokinetic profile as rapid and as advantageous to both preserve some of the physiologic
consistent. However, I acknowledge that the ability to advantages gained by IV acetaminophen and avoid the
achieve IV access cannot be assumed in the field. need for obtaining IV access or placing a nasal gastric
tube. However, to make the IM route feasible, a more
Oral administration is characterized by relatively high concentrated formulation would be required from the
bioavailability (85–93%) but varying early plasma con- manufacturer, as the Orfirmev concentration is 1g in a
®
centrations such that the concentration may remain 100mL vial, which is too dilute for IM use. At this time,
1
subtherapeutic for as long as 60–80 minutes. I do not I am unaware of any data on the pharmacokinetics of
have information on whether the rapid-release gel cap the IM route. This is probably due to the lack of an IM
formulation described by SGM Bowling significantly formulation.
decreases time to peak plasma concentration compared
with a pill or capsule. However, it could be considered Disclaimer
as an option for the field medic who cannot administer
IV acetaminophen. The views expressed in this article are those of the au-
thor and do not necessarily reflect the official policy or
It should be noted that oral administration is subject to position of the US Fleet Forces Command, the Depart-
hepatic first-pass metabolism. Avoidance of the portal ment of the Navy, the Department of Defense, or the US
circulation and hepatic first-pass exposure is one of the Government.
2
major advantages of the IV route. While there is scant
evidence that acetaminophen toxicity occurs at thera- References
peutic dosing, even in chronic liver disease, in overdose
the mechanism of toxicity is the exhaustion of hepatic 1. Smith HS. Perioperative intravenous acetaminophen and
glutathione stores in the liver during first-pass metabo- NSAIDs. Pain Med. 2011:12:961–181.
lism. This highlights the importance of properly docu- 2. Candiotti KA. Safety of multiple-dose intravenous acetamino-
3
phen in adult patients. Pain Med. 2010;11:1841–1848.
menting the time and dose of acetaminophen, regardless 3. Benson GD, et al. The therapeutic use of acetaminophen in
of the administration route, before medical evacuation, patients with liver disease. Am J Theraps. 2005;12:133–141.
in order to avoid inadvertent overdose due to subse-
quent administration of acetaminophen at higher ech-
elons of medical care.
CDR Vokoun graduated from the University of Texas
Another possibility for use of acetaminophen in a patient Southwestern Medical School. He is a board-certified
unable to take oral medication would be acetamino- anesthesiologist who has served as head anesthesiologist
phen suppositories. This is a very common perioperative at a Role 2 in Afghanistan. He is currently the senior
pain strategy in the pediatric population. Suppositories medical officer at Explosive Ordnance Group Two and
are small, lightweight, and easy to place. Unfortunately a staff anesthesiologist at Naval Medical Center Ports-
rectal administration requires 4 hours to achieve peak mouth, Portsmouth, Virginia. He can be reached at
plasma concentration. Rectal formulations are associated Edward.vokoun1@navy.mil.

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