Anaesthetics 'could worsen pain'

Some anaesthetics are irritant chemicals
Some general anaesthetics could actually worsen the pain following surgery, say scientists.

So-called "noxious" anaesthesia drugs - used commonly worldwide - stimulate nerves to cause irritation long after the operation is over. The US research, published in Proceedings of the National Academy of Sciences journal, could prompt the choice of different drugs. A UK expert said solving post-surgical pain was a priority for anaesthetists.

Anaesthetists have known for some time that certain drugs, such as the gas isoflurane, while very effective at rendering and keeping patients unconscious, are actually irritant chemicals. Some already use a painkilling drug to lessen this effect before delivering the anaesthetic itself. The latest finding, by research staff at Georgetown University Medical Center however, suggests that effects of the irritant is not just short-lived, but lingers on long after both the painkiller and the anaesthetic have worn off.

The drugs act on the same receptors on nerve cells which are activated by contact with other irritants, such as garlic, mustard or chilli.

Mice bred without these receptors were unaffected by the "noxious" anaesthetic gases.
If strongly activated, these can lead not just to an immediate sensation of pain, but also a longer oversensitisation of pain pathways in the nervous system.

In patients, this might mean that the pain they feel after an operation is significantly increased.

Switching drugs
Dr Gerard Ahern, who led the study, said: "It was not really recognised that use of these drugs results in the release of lots of chemicals that recruit immune cells to the nerves, which causes more pain of inflammation.
"The choice of anaesthetic appears to be an important determinant of post-operative pain."

He said that while this effect could be reduced by using other types of anaesthetic, these might not perform as well in other ways.

Professor Ian Power, from the University of Edinburgh, said that post-operative pain remained a serious problem, despite advances in anaesthesia over the decades.
"We are very aware that acute post-operative pain can persist and become chronic and long-lasting, and we have been looking for reasons for that - perhaps this research may provide those.
"If this research were to be validated and proved correct, it would be fairly easy for anaesthetists to move from one type to another."

Professor Richard Langford, a consultant in anaesthesia and pain management at Bart's and The London NHS Trust, said that while the findings were interesting, there was no guarantee a similar effect would be detected in humans undergoing surgery.
"There are a myriad of different factors that combine to produce the experience of pain, including the degree and size of the surgery, and the mood or level of anxiety in the patient."

Pregnant Women, Children Cautioned on Dental Mercury (Update1)
By Avram Goldstein

June 5 (Bloomberg) -- The mercury in dental fillings may have toxic effects on fetuses and young children, U.S. regulators said for the first time as part of a legal settlement.

After decades of debate about the safety of mercury amalgam dental fillings, the Food and Drug Administration added the statement on ``safety concerns'' to its Web site this week, said agency spokeswoman Peper Long in a telephone interview today. The FDA agreed to post the warning about the dangers for developing human brains to settle a lawsuit by a collection of environmental groups, consumers and state officials.

In the settlement, the FDA agreed to bring to a conclusion by July 2009 a regulatory review of mercury in fillings that began in 2002. The process could result in a requirement that prescribing information warn dentists and pregnant women of nervous system dangers to fetuses and young children with developing brains, Long said.

``Gone are all of FDA's claims that no science exists that amalgam is unsafe,'' said Michael Bender of Vermont, a plaintiff in the lawsuit, in a statement today on PR Newswire. ``The FDA has moved to a more neutral course, while still recognizing the serious health risks posed by amalgam in particular for children and unborn children, for pregnant women, and for those with mercury immuno-sensitivity.''

Mercury is a neurotoxin that can interfere with brain growth and has been shown to affect cognitive and motor-skill development, according to the Environmental Protection Agency.

Dental Association

The American Dental Association, the largest group of U.S. dentists, said the settlement amounts to little because it doesn't change the current use of mercury. Cavities are filled with the amalgam, made of mercury and a powder containing silver, tin, copper, zinc and other metals. Dentists have used it for more than 100 years.

``Dental amalgam remains a safe, affordable and durable cavity-filling choice for dental patients,'' the dental group said in a statement today on PR Newswire. That belief, the group said, is based on ``extensive studies and scientific reviews of dental amalgam by government and independent organizations worldwide.''

An FDA panel of independent advisers voted 13 to 7 in 2006 to reject the agency's conclusion that the available literature supports continued use of mercury in fillings. The agency had said it reviewed 34 studies and found no evidence the metal releases harmful mercury vapors in the mouth from chewing or during dental procedures.

Data Sought

Many members of the panel, which included doctors and dentists, said the risks associated with mercury fillings can't be quantified without better data on short-term exposure and certain patient groups. About 30 percent of the more than 150 million fillings placed in the U.S. each year are made of amalgam.

Patient advocates urged the panel to recommend that the FDA ban amalgam in favor of tooth-colored composite resins, which they said are safer and just as effective.

Dentists argued that fillings containing mercury are stronger, cheaper and more durable, and said the amount of mercury exposure from fillings is minuscule when compared with fish and other dietary sources.

The lawsuit was filed in December in U.S. District Court in Washington and then assigned by a federal trial judge to a magistrate who served as a mediator, Long said. FDA officials added the cautionary language to the agency Web site on June 3 with ``uncharacteristic speed,'' Bender said.

The case is: Moms Against Mercury v. Eschenbach, 07cv2332, U.S. District Court for the District of Columbia.