When Viagra first hit the market, there was hope it might work in women as well as men, giving a pharmacological boost to those with low levels of sexual arousal (referred to clinically as “female sexual dysfunction” or “female sexual arousal disorder”).

With the possible exception of woman who experience loss of libido as a side-effect of antidepressant drugs, that hasn’t turned out to be the case.

But now scientists at Pfizer, the company that markets the little blue pill, claim to have made an advance that could eventually lead to a female version of the wonder drug.

Their rather dry write-up is titled “UK-414,495, a selective inhibitor of neutralendopeptidase, potentiates pelvic nerve-stimulated increases in female genital blood flow in the anaesthetized rabbit.” It appears in the British Journal of Pharmacology.

Ironically, the subjects of their research were rabbits, whose reputation suggests they don’t need much help in the breeding department, but whatever.

According to the scientists, UK-414,495 enhances blood flow to a female rabbit’s clitoris and vagina after its pelvic nerve is stimulated. It does this by blocking destruction of VIP, a neurochemical that dilates blood vessels.

Viagra, in contrast, works by increasing nitric oxide availability in the small blood vessels of the penis…a completely different mechanism from UK-414,495. No wonder it doesn’t do diddly for women!

Although the experimental drug in this study isn’t fit for human use, the Pfizer scientists say their work may unlock the door to other compounds that are.

Even if that were the case, they add that “the translation of results obtained in the rabbit to humans is unknown, especially since the link between blood flow and subjective arousal remains controversial.”  Apparently however, some studies do suggest that women with arousal disorders are helped by enhanced genital blood flow.

Multaq, an expensive new drug for the treatment of atrial fibrillation, is only half as effective as amiodarone, its generic congener, and it has a similar side-effect profile according to Sanjay Kaul and colleagues at Cedars-Sinai Medical Center.

As a result Multaq should be reserved for patients in whom amiodarone is ineffective or associated with intolerable side-effects, the scientists concluded in an op-ed piece in the Journal of the American College of Cardiology.

Their conclusion is based on a review of 3 clinical trials (summarized below). It represents a huge setback for Multaq, which was at one time touted to be a potential blockbuster with annual sales in the billions.

Multaq “has only modest efficacy and no clear-cut safety advantage,” Kaul told the LA Times. The drug costs $9 per day, whereas amiodarone costs just a few cents. “Why would you want to use an expensive, ineffective alternative?”

Atrial fibrillation (AFib) affects 2.3 million Americans and causes about 71,000 deaths per year.

Afib is characterized by chaotic electrical and muscular activity in the upper chambers of the heart. The condition can predispose patients to strokes and can cause fatigue, dizziness, loss of consciousness or heart failure.

Amiodarone is highly effective in restoring normal cardiac rhythm in patients with Afib, but it is associated with frequent, potentially serious abnormalities of thyroid and lung function. Multaq was developed by Sanofi-Aventis as an alternative. 

The first trial showed that Multaq doubled the risk of death in patients with moderate- to high-risk for hospitalization and death from Afib.

The second showed that Multaq reduced hospitalizations from Afib, but there was no impact on mortality in lower risk patients.

The third revealed that Multaq was half as effective as amiodarone in preventing hospitalizations and deaths. There was no difference in the incidence of side-effects.

Everyone knows that people react differently to pain: the initial jab of Novocain at a dentist’s office causes excruciating discomfort for some, while others barely seem to mind. But is that because some people truly feel more pain than others in a given circumstance (such as an injection) or because some people can just suck it up better?

A new study by Frank Reimann and colleagues at Cambridge Institute for Medical Research suggests the former may be true, even though it doesn’t completely rule-out the whimp factor.

Reimann’s group reported in the Proceedings of the National Academy of Sciences that variations in the SCN9A gene were associated with changes in the perception of pain.

To reach this conclusion, they studied kids with a rare condition characterized by an inability to detect pain. These kids can pass knives through their arms and walk across hot coals without a flinch. Reimann’s group found this extremely maladaptive condition was associated with a nonfunctioning SCN9A gene.

The scientists reasoned that polymorphism at the SCN9A locus could cause differing pain thresholds, and tested their hypothesis by examining DNA from 578 people with osteoarthritis. They found that folks having a common variant of the SCN9A gene had lower pain self-assessment scores than those having a rarer form of the gene.

The scientists reproduced their findings in people with back pain, pancreatitis and phantom limb pain.

The SCN9A gene it turns out, codes for a membrane-bound protein on pain sensory nerve cells. The protein is involved with triggering those cells, which then relay a pain message to the brain. Apparently, the version of the protein created by the rare SCN9A decreases firing thresholds in the cells so they are more likely to relay bad news.

How’s this for a cool high-school science project?

Brenda Tan and Matt Cost, a pair of students at Trinity High School in Manhattan, recently performed DNA analysis of food items and other objects collected in their homes and surrounding environs.

They found a hellacious mix of mislabeled and possibly tainted food items and raised a ton of questions in the process.

Among their notable discoveries:
-  A pricey chunk of so-called sheep’s milk cheese turned out to have been derived from cow’s milk,
-  Fish labeled smelt turned out to be Japanese anchovy,
-  “Venison” dog treats were actually made from beef
-  Sturgeon caviar samples contained DNA from that widely-known delicacy, the Mississippi paddlefish.

The students dubbed their project “DNAHouse.” They analyzed their collections using the Barcode of Life Database which is normally used in species identification. They secured help from DNA barcoding experts at Rockefeller University and the American Museum of Natural History for their project.

A write-up of their work appears here.

“We do not know where or why the mislabeling occurred, but most cases appeared to involve substitution of a less expensive or less desirable item, suggesting the possibility of deliberate mislabeling for economic gain,” the authors wrote. “We also think mislabeling is a serious problem because certain individuals have allergies or dietary restrictions regarding certain foods.”

Trinity has a track record for producing these kinds of stories. Last year, 2 other Trinity students created a stir by reporting that one-quarter of the fish at local markets and restaurants was mislabeled.

Of note, Tan and Cost also sampled hair from several classmates. “We were happy to report,” they wrote, “that our classmates came back as 100% human.”

Ever wonder how safe and reliable Granny’s new pacemaker is? In most cases it turns out nobody really knows, because the quality of the evidence used by the FDA to approve these devices is poor, according to a study published in JAMA last week.

Sanket Dhruva and colleagues from UCSF drew these conclusions after examining the premarket approval process (PMA) for 78 high-risk cardiovascular devices that received FDA approval between January 2000 and December 2007.

PMA is the most stringent FDA review process for medical devices. The scientists found that 65% of the PMA applications for devices were supported by exactly one study.

And overall, the quality of the studies was abysmal. Some failed to provide details like the number of enrolled participants. Only 27% of them were randomized and even less, 14%, were blinded (blinded, randomized, controlled trials represent state-of-the-art scientific research).

The scientists concluded that in general, the FDA’s premarket approval process for cardiovascular devices lacked statistical firepower required to control for bias and hence draw valid conclusions.

The scientists understood that it is more difficult to subject medical devices to blinded studies, since there is no way to produce a “sugar pill” (that is, placebo) for medical devices.

“But we were surprised that so many devices were approved on the basis of a single study,” Dhruva told the Los Angeles Times.

The FDA started approving medical devices in 1976. Recently, there has been a marked increase in the number of cardiovascular devices implanted in Americans.  In 2008, 1.2 million people received stents in the US alone. 350,000 people received pacemakers and 140,000 received implantable cardioverter-defibrillators.

The radiation produced by CT scans performed in 2007 will cause 29,000 cancers and kill 14,500 Americans, according to a study published in the Archives of Internal Medicine. 

To reach this conclusion, Amy Berrington de Gonzalez and colleagues from the National Cancer Institute used a computer simulation to estimate the impact of the 70 million or so CT scans that were performed in the US that year (only 3 million were performed in 1980).

The scientists estimated that about a third of the future cancers will occur in people who were between the ages of 35 and 54 when they received their CT, and 15% of them will develop in people who were children or teens when the scan was performed.

About two-thirds of the new cancers will develop in women, since they are more vulnerable to radiation.

“There is a significant amount of radiation with these CT scans, more than what we thought, and there is a significant number of cancers,” Rita Redberg, the editor of the Archives of Internal Medicine, told the LA Times.

“While certainly some of the scans are incredibly important and life saving, it is also certain that some of them were not necessary,” Redberg added.

CT scans provide pristine images by combining data from multiple x-ray images. They can also expose patients to up to 400 times more DNA-damaging radiation than conventional chest x-rays. 

In another study, Rebecca Smith-Bindman and colleagues from UCSF found that radiation exposure varies almost 13-fold for different kinds of CT studies, from about 2 millisieverts for a routine head CT scan to 31 millisieverts for a scan of the abdomen and pelvis.

The average American receives about 3 millisieverts of radiation per year, a level not considered to be a health risk.

In the last 3 decades, Americans have reaped enormous health benefits by smoking less, but have lost ground due to weight gain and obesity, and their negative impacts on health. Ever wonder how these competing trends interact with each other?

Susan Stewart of Harvard University and colleagues tried to answer this question by forecasting life expectancy for a nationally representative 18-year-old assuming that recent trends in smoking and weight gain continued for the next decade or so.

The scientists estimated cigarette smoking trends over the last 30 years using data from the National Health Interview Survey, and BMI data from the National Health and Nutrition Examination Survey.

It turned out that the negative effects of increasing body mass index swamped the positive effects of cigarette smoking declines.

Specifically, continued declines in cigarette smoking would increase the life expectancy of an 18-year-old by 0.31 year by the year 2020. However, continued escalations in BMI would cut life expectancy by 1.02 years over the same period of time, with an overall net loss in life expectancy 0.71 years.

The scientists did mention that other factors such as better nutrition and education are likely to generate a very modest increase in life expectancy despite the impact of obesity, at least through 2020.

But at some point, the authors concluded, a failure to address continued increases in obesity could erode the steady gains made in health over the last century.

It’s “a bit of a wake-up call,” senior author Allison Rosen told the Los Angeles Times. “We have attributed so many of our health problems to smoking, and we’re getting health improvements from declines in smoking. But changes in the rates of obesity are starting to outweigh the declines in smoking.”

The write-up appears in the New England Journal of Medicine.

In the last decade, ultra endurance sports like triathlons and cycling marathons have grown in popularity. The granddaddy of these extreme sports is the Western States 100-Mile Endurance Run, which courses through the Western States Trail in Northern California. The first running was held way back in 1976.

Recently, scientists from the Virginia Commonwealth University and the Department of Veterans Affairs Northern California decided to have a look at the 3,500 people who have entered this event over the years.

They found dramatic trends in the demographics and results of the participants.

For example, the average age of race starters was 41 back in 1986, but between 2000 and 2007 the average age had risen to 45-47.

In addition, many more women now compete in the race. From 1986 to 1988, between 10-12% of the competitors were female. Since 2001 however, that percentage has nearly doubled to 20-22% of the competitors.

The scientists attribute this to the fact that more women in their 40s and up, and more men in their 50s and up have signed up for the race, while fewer men who were less than 50 have entered.

And these older runners have delivered. Every year since the inception of the event, the average age of the top 5 finishers has gone up. Initially this number was in the early 30s, but now it is in the late 30s. This phenomenon is mostly attributable to changes in finish times for women, which the scientists say have improved by 37 minutes per decade since 1980.

This means that the finish time difference between the top men and women has been cut by 4% per decade, to a margin of 14% in 2007.

The study appears in Medicine & Science in Sports & Exercise.

For the second time this year, a clinical trial has shown that the cholesterol-lowering drug Zetia does not prevent heart disease.  

The first trial appeared last January. That trial compared Vytorin—a blockbuster drug that combines  the active ingredient in Zetia with a generic cholesterol-buster known as simvastatin—against simvastatin alone in patients with a genetic condition causing them to have very high levels of LDL (bad) cholesterol and premature cardiovascular disease.

In that trial, Vytorin reduced LDL cholesterol levels much more than simvastatin alone but surprisingly, atherosclerotic plaques actually grew faster in the coronary arteries of the patients taking Vytorin.

The news was greeted with a precipitous fall in prescription volume for both Zetia and Vytorin.

The second study was published last week in the New England Journal of Medicine. This study compared Zetia to Niaspan, a drug that raises blood levels of HDL (good) cholesterol.

In the second study, Allen Taylor of the Walter Reed Army Medical Center and colleagues enrolled 363 people with coronary artery disease that had been taking statins for many years. 

Taylor’s group found that Niaspan shrank carotid artery plaques by 2%, but Zetia had no such effect, even though it effectively reduced cholesterol levels (as it did in the first trial). In addition, patients who received Niaspan sustained 2 heart attacks or heart-related deaths during the study, while 9 patients receiving Zetia suffered that outcome, a significant difference.

Zetia “should be better for the arteries and it wasn’t,” Taylor told reporters covering last month’s American Heart Association meetings. “The drug wasn’t operating as you would expect.”

Officials at Merck, which co-markets Vytorin, said the study wasn’t large enough to draw firm conclusions and that larger trials of a similar nature are underway. Stay tuned.

Occupational exposure to bisphenol A (BPA) is associated with erectile dysfunction, loss of sexual desire and ejaculation difficulties, according to US and Chinese scientists. Their report is one of the first to show this negative association in humans. Numerous earlier studies had done so in animals.

BPA is chemically similar to estrogen. It is used to produce polycarbonate plastics, and can be found in baby bottles, water bottles and cans used to package food and beverages.

The chemical leaches from these products into food, and can be detected in the urine of nearly every American.

In animal studies, BPA had been associated with infertility, early onset of puberty, weight gain, cancer and diabetes.

Last summer, the FDA issued a provisional ruling that BPA is safe at levels found in the US population. That ruling was disputed by its own advisory panel. Many places including Canada have banned BPA from baby bottles.

De-Kun Li and colleagues studied 634 Chinese factory workers. Of these, 230 were exposed to high levels of BPA on the job, and 404 had no such occupational exposure.

The scientists measured BPA levels in the air and the worker’s food and in their urine as well. At the same time, they surveyed workers about sexual experiences.

Workers with occupational exposure to BPA had more than 4 times the risk of erectile dysfunction, were 4 times more likely to report low sexual desire, and were 7 times more likely to experience ejaculation difficulties. The risk of these problems increased with urinary BPA concentrations.

The factory workers’ urinary BPA levels were about 50 times higher than that found in US males.

“Critics dismissed the animal studies, saying, ‘Show us the human studies,’” Li told the Los Angeles Times. “Now we have a human study and this can’t be dismissed,” he added.

The study appears in Human Reproduction.