Call It A Comeback? The Many Faces of Nitrous Oxide For Labor Pain Relief

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Call It A Comeback? The Many Faces of Nitrous Oxide For Labor Pain Relief


A long-neglected drug for relieving pain in labor may be making a comeback in the United States.

Twenty-five years ago, Evan McAllister tried to bring Entonox, a premixed gas blend consisting of 50 percent nitrous oxide and 50 percent oxygen from the U.K. to the United States under the name Dolonox. McAllister, a respiratory therapist with a background in anesthesiology, hit a roadblock with the Food and Drug Administration, who denied the application for what he calls “compliance reasons.”

The U.S. FDA grandfathered in older medical gases, including nitrous oxide and oxygen shortly after the turn of the century. A blend of these two medical gases is treated as a new drug, which requires extensive (and expensive) research to be approved.

Determined to make nitrous oxide available in the U.S., McAllister designed a device to blend pure oxygen with pure nitrous that could be self-administered by the patient. The device was in production until about 20 years ago, when sales dropped off and McAllister stopped making them.

As a result of recent interest in nitrous oxide as a labor analgesic, McAllister and his company, Nitrox, Inc., designed a more compact version of the decades old blending unit, which they are actively marketing.

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Said McAllister, “I’ve had it all shut down for 25 years and it’s all coming back.”

Nitrous oxide for labor?

Unlike women in Canada, the U.K., Scandinavian countries, Australia and elsewhere, women of childbearing age in the United States are likely to have never heard of the use of nitrous oxide for pain relief in labor. Only three hospitals in the U.S. offer the option of self-administering nitrous oxide during labor: University of California, San Francisco (UCSF), University of Washington Medical Center in Seattle, and St. Joseph Regional Medical Center in Lewiston, Idaho.

Dr. Mark Rosen of UCSF conducted a systematic review in 2002 to determine the efficacy and safety of nitrous oxide for labor analgesia. While nitrous oxide is not a potent labor analgesic, Rosen concluded that “it is safe for parturient women, their newborns, and health care workers in attendance during its administration” and effective enough for many women.

The 50/50 mixture of N2O with oxygen used in hospitals is eliminated through the lungs, not the liver, making it a safe option for mother and baby if self-administered properly. Rosen was quoted in a 2007 article in the Journal of Midwifery & Women’s Health saying “We’ve never seen a groggy baby from inhalation of 50% N2O. It just doesn’t happen.”

McAllister’s blending unit limits the upward amount so a woman cannot overdose, taking pure oxygen and pure nitrous, blending them 50/50, and putting them it into a system where the patient can breathe on demand through out her labor. Said McAllister, “Wherever the woman is at, she’s in total control.”

An epidural monoculture

In a comprehensive interview on childbirth education organization, Lamaze International’s blog, Science and Sensibility, in April 2010, Judith Rooks discussed the roadblocks encountered in trying to make nitrous oxide available in U.S. hospitals. While lack of equipment has been problematic, fear of competition and potential loss of revenue have held progress at bay. Rooks told Science and Sensibility’s Amy Romano:

Epidurals are big money makers for hospitals and, of course, for anesthesiologists, whereas nitrous oxide is an old, off-patent, cheap drug that can’t compete as a money- maker…Profit is a powerful force in American health care. If no one is making a profit, no one is pushing for a product to have a place on the shelf, whereas those who are making big profits are always trying to push the product that is not profitable off the shelf.

According to Rooks, the drive of anesthesiologists, obstetricians and hospitals is to maintain what she labeled in a previous article, an “epidural monoculture.” If a hospital is to promise women that they can have an epidural during labor, this service must be available 24/7 every day of the year, since any women may go into labor on any day before or after her “due date.” More than 5 full-time anesthesiologists or nurse anesthetists would be required, and making their salaries justifiable to the hospital depends upon a high percentage of women getting epidural anesthesia.

Additionally, some obstetricians and hospitals are reluctant to use it because of perceived risk of environmental contamination, even though modern nitrous oxide units scavenge the unused gas. Rooks calls this concern a red herring, as hospitals are filled with many types of potential occupational hazards and safety programs are put in place to train staff accordingly.

Nitrous oxide is notoriously bad-mouthed, called old-fashioned, dangerous and a revenue reducer, an attitude partly stemming from what Rooks describes as “a desire to avoid the need to provide the time-intensive care needed by women who are experiencing some degree of pain.” Rooks cites her personal experience with an obstetrician who “banned continued use of nitrous oxide analgesia in an major university hospital when he went there to head the department of obstetrics and gynecology during the 1990s,” finally admitting to Rooks that he prefers the use of epidurals because he is uncomfortable seeing women in pain, favoring a quiet labor ward.

Difficulties in introducing nitrous oxide to the U.S. market have a nearly century-old history. In a 1922 New York Times article about nitrous oxide for laboring women, the doctor interviewed (who specifically asked that his name not be printed) spoke to similar challenges as to why the nitrous oxide was not regularly used instead of chloroform and ether.

“The first answer is that the medical profession is the most conservative of bodies. The second answer is concerned with economics. I told you that I believe that a doctor must be present while the gas is in use, which is for the duration of ten or twelve hours possibly—used periodically, remember. And remember also that some of my colleagues do not agree with me on that point. I have a wife and four children to support. I am an attending physician at three hospitals. If I stayed ten or twelve hours with each patient I could not make a living for my family unless I charged a fee far beyond the means of the average person. The presence of a professional anesthetist would, of course, make my presence unnecessary until the very last stage, but it would add materially to the cost as far as the patient was concerned.”

Consumer interest

Joyce Moxley Thomas, a midwife and advocate for nitrous oxide in Chino, California, believes that nitrous oxide is not available in U.S. in part because the FDA’s classification of the premixed gas as a new drug and the expense associated. Thomas became aware of the benefits of nitrous oxide while working with U.K. midwives, whom she feels take its availability for granted.

“To get a drug approved by the FDA takes years and costs millions,” said Thomas, “which BOC/Linde Gas is not interested in paying.”

Thomas is convinced that the middle ground of using nitrous oxide will be widely appealing to U.S. women.

“I think when American women realize that since the 1950s women worldwide have had access to [nitrous oxide] and expect to have it there for their births– that we have been deliberately deprived of a safe, effective “gas and air” that is not narcotic, that didn’t hurt our babies, and allowed us to give birth normally — I think American women will start demanding it,” said Thomas. 

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