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Rabu, 18 November 2009

Genzyme's "Remarkable Business'Strategy" and Contaminated Drugs

In June, 2009, an article in the Boston Globe described how the Boston area based biotechnology company Genzyme sold some astonishlingly expensive drugs, using
a remarkable business strategy: In countries from Colombia to Taiwan to Libya, the Cambridge firm has compiled an extraordinary track record of searching out patients like Tania, providing desperately needed treatment, and then successfully pressing their governments, even poor ones, to pay full price for the most expensive drugs in the world.

The article focused on how Genzyme marketed Cerezyme for Gaucher's disease.
When Genzyme Corp. first introduced a bioengineered drug for Gaucher (pronounced GO-shay) disease in the 1990s, the very idea seemed almost absurd to most people in the pharmaceutical industry. It was expensive to manufacture, there were vanishingly few known patients, and it wasn't clear how you could sell enough of it to recoup research costs, never mind make a profit.

Genzyme's solution, elegant in its way, was to set a price high enough to earn a substantial profit no matter how small its pool of patients. Then the company surprised the medical world - and its investors on Wall Street - by showing that American health insurers could be persuaded to pay the six-figure price tag. And with the only effective treatment for Gaucher disease, Genzyme never needed to lower the price, even as production efficiencies raised profit margins on the drug to as much as 90 percent.

The drug started to bring in tens of millions of dollars a year, then hundreds of millions. Today this one drug, prescribed for about 5,000 patients, has transformed Genzyme and its chief executive, Henri Termeer, into one of the great success stories of biotechnology, fueling its expansion into a $16 billion company with offices and factories worldwide.

By the early 2000s, Genzyme had reached most of the known Gaucher patients in the United States, so it had begun pushing outward to new markets. Genzyme created divisions within the company to find overseas patients; it hired experts to cajole balky governments into paying for the patients' Cerezyme doses. Some of the company's successes were extraordinary: hundreds of patients in Brazil. Patients in Taiwan, Kuwait, and Bulgaria. The government of Libya's Colonel Moammar Khadafy pays for Cerezyme for a handful of patients.

As it notched these successes, the company stayed largely under the radar of public health activists who were pushing drugmakers to discount AIDS drugs and other lifesaving medications whose retail prices were financially out of reach to many governments.

Biotechnology drugs like Genzyme's, though crushingly expensive for each patient, were so rarely prescribed that they did not attract the same attention, and Genzyme followed an extremely disciplined 'one price' strategy: find patients; donate the drug at first if necessary, but press constantly to be paid full retail price.

The "one price" for Cerezyme in Costa Rica was $160,000 per year of therapy.

I thought about posting about this story when it came out, focusing, of course, on the amazing price of Cerezyme. However, then I wondered: while the price of Cerezyme seemed extremely high, could anyone say that it was outrageously and unfairly high? After all, the drug was expensive to develop and produce, could not be sold in volume, and provided apparently very effective treatment for an otherwise untreatable disease. So I put the article in a file, and did not post about it.

Then a few days later, another story ran in the Globe, this time about problems in the Genzyme plant that produces Cerezyme:
n an unprecedented move for Genzyme Corp., the state’s largest biotechnology company has halted production of two drugs for rare genetic disorders after a virus was discovered in production equipment at its Allston plant.

The drugs are used by 8,000 people worldwide and cost about $200,000 per patient annually. While the virus has the ability to taint the drugs, it is not considered harmful to humans, officials said. The manufacturing plant will remain shut through July while it is decontaminated as a precaution.

Shipments of the drugs, Cerezyme and Fabrazyme, have been put on hold while the US Food and Drug Administration seeks assurance from the company that none of its inventory is compromised. Genzyme officials believe the inventory was not affected.

The current supply will need to be rationed, Genzyme said.

My first thought was that if Genzyme can charge so much for Cerezyme, at least it ought to be able to afford a pristine production process. On the other hand, I also realized that manufacturing processes in biotechnology are complex and difficult, perfection is not always possible, and the contamination in question did not appear harmful. So I put this article in the file too, and did not post about it either.

Four days ago, the Boston Globe published yet again about troubles in same manufacturing plant.
Genzyme Corp., the Cambridge biotechnology giant that has spent five months scrambling to regain its footing after detecting a virus at its Allston plant, is facing a new contamination problem: bits of steel, rubber, and fiber found in drugs made by the company and shipped from the same site.

Federal regulators yesterday warned doctors to look for foreign particles in five Genzyme drugs used to treat rare genetic disorders, including two - Cerezyme and Fabrazyme - that have been rationed because of the viral contamination detected in the Allston Landing plant last summer. The five drugs represent roughly half of Genzyme’s $4.6 billion in annual sales.

Particles are believed to have been found in less than 1 percent of the Genzyme drugs based on product lots examined, according to a statement from the Food and Drug Administration. The FDA warned physicians, however, to carefully examine vials of the products and filter them before they are given to patients - steps that are considered standard procedure within the industry. If they find particles, the FDA asked for the vials to be returned to the manufacturer. The agency warned that ingesting the particles could have effects that include allergic reactions and blood clotting.

FDA inspectors arrived at the Allston plant last month to begin an investigation into Genzyme’s production operations.

In addition, a New York Times article noted:
'Biological manufacturing is extremely complex and prone to problems,' including contamination, said Jean-Jacques Bienaime, chief executive of BioMarin Pharmaceuticals, a biotech company that also makes drugs for rare diseases, including one it co-developed with Genzyme. Mr. Bienaime said his company always maintained at least a year’s worth of inventory in case of a production outage.

But Genzyme did not have such an inventory of Cerezyme and Fabrazyme.

Finally, today the In Vivo blog posted a discussion of Genzyme's production woes which suggested that the two different types of contamination at the plant, and the failure of the company to reliably ship pure, unadulterated drug to patients were not simply the results of bad luck or failure to attain unattainable perfection.
Friday's announcement that bits of rubber and other detritus were found in vials of five different drugs manufactured at Genzyme's beleaguered Allston Landing plant was worthy of the satirical publication "The Onion"--except that it was true.

The picture grew murkier over the weekend, with the arrival of another Form 483 missive from FDA about ongoing manufacturing issues and a complete response for Lumizyme, Genzyme's enzyme replacement therapy for Pompe disease has been subject of more regulatory twists and turns than the plot of a Dan Brown novel.

The origin of the problem goes back three years, to the original approval of Myozyme, basically the same drug as Lumizyme only manufactured on a much smaller scale, at a 160-liter scale facility in Framingham. Genzyme underestimated the demand for the drug, and plans to shore up capacity with a 4000-liter facility in Belgium were put in place. Only as a stop gap, the company also decided to devote 1/6th of its manufacturing capacity at Allston to the making of the drug.

And that decision has proved problematic. The stress of running an aging plant full tilt meant there was no time for necessary facility upgrades that might threaten the inventory of drugs manufactured at Allston, among them Cerezyme for Gaucher disease and Fabrazyme for Fabry disease. Genzyme CEO Henri Termeer admitted as much in the Nov. 16 investor call, noting '"the introduction of the production of Myozyme in Allston was a very significant factor in the complications we have experienced there.'

Too bad that realization didn't happen one year ago. That's when regulators started sending warning letters outlining concerns related to what sound like bread-and-butter manufacturing issues: microbial monitoring, equipment maintenance, and process controls.

What's most amazing is that problems are ongoing. Recall that six-week interlude this summer when the firm took the entire plant offline to sterilize it after discovering yet another unrelated problem--several bioreactors contaminated with a non-lethal to humans but problematic Vesivirus.

On the company's Nov. 16 call to investors, management confirmed that the latest 483 letter relates not to a new problem created by Genzyme's decontamination efforts but arising because of 'an older piece of equipment'. As Genzyme's EVP of Therapeutics, Biosurgery, and Corporate Operations said during a Q&Asession with analysts, '"There was a number of issues there that they [regulators] highlighted and many of which we were very aware of and working to address.'

Management's solution? Take the plant off line again for a few weeks to, as Meeker puts it, 'allow us to move more quickly to address those issues.' Does everyone feel better now?

In some strange way, the very minor nature of these gaffes is the most damning element of the story. It throws management's judgment into question and again casts doubt on the ability of the current team to resolve a situation that should never have escalated to this level.

So now it is time to discuss Genzyme's production woes on Health Care Renewal.  For $160,000 a year, it seems reasonable to expect that patients could expect a reasonably well-thought out, conservatively planned production process that would be able to reliably produce sufficient quantities of pure, unadulterated drug.  Instead, Genzyme's "remarkable business strategy" did not seem to include adequate maintenance of production facilities with adequate capacities, or even keeping an adequate reserve supply of product in anticipation that over-working a single aging facility with aging equipment might lead to something breaking down. 

By the way, for overseeing this "remarkable business strategy," Genzyme paid its CEO, Henri A Termeer, $13,773,782 in total compensation last year (per the 2009 proxy statement).  Presumably mainly from the stock and option awards he has accumulated over the year, Mr Termeer now owns 4,080,387 shares of Genzyme stock, 1.5% of total outstanding shares.  For that money, patients, share-holders, and line employees ought to expect "remarkable business strategies" that include attention to such basics as good maintenance of production facilities. 

Maybe the company's well compensated (more than $400,000 a year) directors should have been more vigilant about overseeing the management's "remarkable business strategy."  The board  included Gail K Boudreaux, an Executive Vice President of UnitedHealth Group, Charles L Cooney PhD, the Haslam Professor of Chemical and Biochemical Engineering at the Massachusetts Institute of Technology, and Dr Victor J Dzau, Chancellor of Health Affairs at Duke University and CEO of Duke University Health Systems, who seemingly have some relevant expertise, although the board also included Richard F Syron PhD, the former CEO of the Federal Home Loan Mortgage Corporation, (Freddie Mac), who resigned in 2008 after the failure of the company which was later bailed out by the US government.   

So once again we see how leaders of health care organizations, in this case perhaps blinded by the prodigious amounts of money they were making, failed to exercise rigorous oversight over how their company produced its product.  The actual production part of biotechnology may seem far less glamorous than other aspects of the company.  Yet, if a drug company cannot reliably produce pure, unadulterated drugs, all its advanced research, cutting edge finance, and glitzy marketing may be for nought. 

This case is another argument for finding health care corporate leaders who remember that long term success comes from putting patients, not dollars, not glitz,  first. 

Selasa, 17 November 2009

Seeking NIH to fund studies on medical ethics, conflicts of interest in medicine and research, and prescribing behavior

Adriane Fugh-Berman MD is principal investigator (PI) of the PharmedOut project. PharmedOut is an independent, publicly funded Georgetown University Medical Center project that educates physicians about industry influence on prescribing. project that empowers physicians to identify and counter inappropriate pharmaceutical promotion practices. PharmedOut promotes evidence-based medicine by providing news, resources, and links to pharma-free CME courses.

PharmedOut is requesting that the U.S. NIH (National Institutes of Health) fund more research into ethics, conflicts of interest, and prescribing behavior. One hundred researchers, clinicians, and ethicists have signed a letter sponsored by PharmedOut asking NIH to fund research on medical ethics, conflicts of interest, and industry influence on prescribing behavior. Stimulus funds have increased the NIH budget by ten billion dollars, but NIH has no mechanism for funding research on how commercial interests affect the choice of medical therapeutics.

Signers include Virginia Barbour MD, Chief Editor of PLoS Medicine, Jerome Kassirer, MD, former editor in chief of the New England Journal of Medicine, Jerry Avorn MD, the Harvard physician who invented academic detailing, Kay Dickersin PhD, Director of the U.S. Cochrane Center, and Susan Wood, PhD, former head of the FDA Office of Women’s Health Research, who resigned over political influence regarding FDA decisions on the emergency contraceptive Plan B. Institutional signers include the Public Library of Science, the American Medical Student Association, the National Physicians Alliance, Consumers Union, the Center for Science in the Public Interest, and the National Women’s Health Network.

The letter, sent to NIH today, is available at http://www.pharmedout.org/NIHLetter.pdf (PDF) and below:


Nov. 17, 2009

From: Adriane Fugh-Berman MD
Department of Physiology and Biophysics
Georgetown University Medical Center
Box 571460
Washington DC 20057-1460
Phone: (202) 687-7845
Fax: (202) 687-7407
ajf29 AT georgetown DOT edu

To: Francis S. Collins, MD, PhD
Director
National Institutes of Health
9000 Rockville Pike
Bethesda, MD 20892

Dear Dr. Collins,

We are writing to ask NIH to fund studies on medical ethics, conflicts of interest in medicine and research, and prescribing behavior. NIH funds a substantial portion of the generation and dissemination of evidence, but the uptake of that evidence and its translation into clinical practice is strongly affected by the complex web of relationships that exists among industry, academicians, medical educators and clinicians.

There is growing evidence that each strand of this web is compromised by ethical lapses and financial conflicts of interest. The recent disclosure of ghostwritten articles, physician payoffs, and the use of academic opinion leaders to increase markets for FDA-regulated products indicate that ethical lapses may permeate biomedical research. A PLoS Medicine editorial in September called ghostwriting “The dirty little secret of medical publishing” and notes “the systematic manipulation and abuse of scholarly publishing by the pharmaceutical industry and its commercial partners in their attempt to influence the health care decisions of physicians and the general public.” [1] An October 1 editorial in the Boston Globe called for a ban on industry speaker fees to physicians. [2] Last month, a commentary in JAMA called for physicians to pay for continuing medical education (CME), [3] citing a recent Institute of Medicine report [4] that criticized physicians’ reliance on industry-funded education.

A stated goal of the NIH is to “exemplify and promote the highest level of scientific integrity, public accountability, and social responsibility in the conduct of science.” Could the muted effect that large, definitive NIH studies, including the WHI, ALLHAT, and CATIE, have had on clinical practice be due to commercial influences? To what extent have ghostwritten articles corrupted the medical and scientific literature? The extent to which industry influences the interpretation of science is unknown.

Dr. Elias Zerhouni, in the September 17th issue of Nature, commenting on Senator Grassley’s investigation of academic medical centers, said “People flouted the rules, didn’t disclose, and did it for years on end, repeatedly.” [5]

In your role as the director of “the steward of medical and behavioral research for the Nation,” we ask that you acknowledge the research gap on the effect of conflicts of interest and commercial influence on medical decisionmaking and set in motion a process that leads to recognition of the importance of funding studies on research ethics, the beliefs and behaviors of researchers and clinicians, and the effects of industry-academic relationships on the generation and dissemination of medical knowledge.

Between bench and bedside lies a path treacherous with ethical quandaries. NIH is the best place to launch and support a scientifically rigorous inquiry into the state of research ethics, industry-academic relationships, and the effect of these relationships on human health. There is currently no identifiable mechanism through which NIH would fund this research.

Your leadership regarding the importance of this issue as one the NIH needs to direct resources towards is essential. We hope to discuss these issues in a face-to-face meeting.

Sincerely,

Adriane Fugh-Berman, MD
Associate Professor, Georgetown University Medical Center
Director, PharmedOut

ajf29 AT georgetown DOT edu
http://pharmedout.org

[and others whose signatures can be seen at the PDF - ed.]

[1] Ghostwriting: The Dirty Little Secret of Medical Publishing That Just Got Bigger. PLoS Medicine, September 8, 2009. http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000156

[2] Keep Doctors Independent; Ban Fees From Drug Makers. Boston Globe, October 1, 2009. http://www.boston.com/bostonglobe/editorial_opinion/editorials/articles/2009/10/01/keep_doctors_independent_ban_fees_from_drug_makers/

[3] Campbell EG, Rosenthal M. Reform of Continuing Medical Education: Investments in Physician Human Capital. JAMA. 2009;302(16):1807-1808.
http://jama.ama-assn.org/cgi/content/full/302/16/1807?home

[4] Institute of Medicine. Conflict of Interest in Medical Research, Education, and Practice. Washington, DC: National Academies Press; April 28, 2009. http://www.iom.edu/CMS/3740/47464/65721.aspx

[5] Wadman M. The Senator’s sleuth. Nature. 2009 Sept;461(17):330-4.

This letter caught my eye, and I expressed support as follows, adding an additional angle to Dr. Fugh-Berman's letter:

Dear Dr. Fugh-Berman,

As a blogger at Healthcare Renewal, I will enthusiastically sign on to and endorse your letter calling on NIH to fund more research into ethics, conflicts of interest, and prescribing. I also wish to add an extended point:

The issues of ethics and conflict of interest also affect healthcare information technology (HIT), and ultimately physician practice. HIT applications are experimental medical devices now being pushed upon physicians via the Office of the National Coordinator and HHS. These medical devices are soon to undergo regulation as such in the EU (pdf report from the Swedish Medical Products Agency here), Canada, the U.S. and other countries as well.

They are used in patient care without patient consent. Their use holds significant potential to monitor and enforce practices deemed appropriate by whomever has the most influence on the bodies controlling the use of these technologies and the data they generate.

From that perspective, and from the perspective of the 2009 National Research Council report that calls for accelerating interdisciplinary research in biomedical informatics, computer science, social science [i.e., the social and ethical implications of health IT], and health care engineering as a sine qua non of health IT success, I believe it is time for NIH to take a leadership role in regulating these devices, conflicts of interest in the health IT industry, and the ethics of their use.

I perhaps should have written "I believe it is time for NIH to take a leadership role in sponsoring research on regulating these devices, conflicts of interest in the health IT industry, and the ethics of their use", rather than calling on NIH to be a regulator. However, until the regulatory affairs concerning health IT are in order, I felt the stronger statement appropriate.

-- SS

Senin, 16 November 2009

The Editorial that Wasn't: Evidence for Systematic Research Manipulation Undetectable by Critical Review

Woe to those of us who have been advocates for evidence-based medicine.  A short description of the evidence-based medicine is medicine whose practice is informed by critical, rigorous review of the best available evidence from clinical research as revealed by systematic search of the published research literature, as well as by the clinician's understanding of biology and the medical and biopsychosocial context, and by the patient's own values.

Evidence-based medicine is based on some key assumptions.  One is that a systematic review will reveal all the results of research studies that are relevant to the issue at hand.  A second is that while the research studies may be flawed and imperfect, they are reported honestly.

Unfortunately, as we have repeatedly discussed, there is more and more evidence that a systematic review will not reveal all relevant results, because research studies may be suppressed, perhaps often, when their results are unfavorable to vested interests.  (Look here for further discussion.)  There is also considerable anecdotal evidence that the design, implementation, and analysis of research studies may be manipulated to make the results more likely to favor vested interests.  (Look here for further discussion.)

An article by Vedula et al just published in the renowned New England Journal of Medicine suggests that such manipulation might be systemic, and that the reporting of manipulated studies may not clearly show what manipulation was done. (1)

To summarize, the authors got access through legal proceedings to internal study protocols and research reports from clinical trials sponsored by Parke-Davis (later merged into Pfizer Inc) of gabapentin (Neurontin) for a variety of clinical problems other than seizures.  Gabapentin was originally marketed as an anti-seizure drug, but Pfizer later "admitted guilt for off-label marketing."  (We discussed the stealth marketing campaign for Neurontin here.)  Vedula et al compared the primary outcome variables specified in the original research protocols, internal research reports, and any publications of the trials' results.  They identified 21 trials, 13 of which were published.  For 12 of the 13, the authors had access to the internal protocol, report, or both.  The main results were:
For 8 of the 12 published trials, there was a disagreement between the definition of the primary outcome in the protocol and that in the published report.... Sources of disagreement included the introduction of an entirely new primary outcome in the published report (in the case of 6 trials); failure to distinguish between primary and secondary outcomes in the published report, even though the protocol did distinguish between them (2 trials); relegation of a primary outcome in the protocol to a secondary outcome in the published report (2 trials); and failure to include in the published report one or more primary outcomes specified in the protocol (5 trials).

Furthermore, it appeared that failure of published articles to clearly and fully report results in terms of the original, pre-specified primary outcome variables occurred when these comparisons were not favorable to gabapentin. As the authors summarized:
Thus, trials with findings that were not statistically significant (P≥0.05) for the protocol-defined primary outcome, according to the internal documents, either were not published in full or were published with a changed primary outcome.

As shown in Figure 3, all the changes that took place between what was specified in the protocol, what was known before publication (as presented in the internal company research reports), and what was reported to the public led to a more favorable presentation in the medical literature of gabapentin's efficacy for unapproved indications.

They concluded:
We are concerned that the reporting practices observed in our analysis do not meet the ethical standards for clinical research or maintain the integrity of scientific knowledge. Fair and honest treatment of patients enrolled in clinical trials of any kind requires full, open, and unbiased reporting. Journal publication, a formalized platform for scientific discourse and dissemination of knowledge, should not be used as a marketing tool for off-label drug use.

Reporting biases such as those we describe here increase the likelihood that interventions will appear to be effective when they are not. Such biases can lead to the omission of negative findings in systematic reviews of intervention effectiveness and in evidence-based guidelines. For example, the 2005 Cochrane systematic review regarding the effectiveness of gabapentin for acute and chronic pain concluded that it is effective on the basis of published findings and should now be updated with the inclusion of unpublished information made available through litigation.

I believe that the article by Vedula et al is particularly important because it shows what appears to be systematic manipulation of the analysis and reporting of multiple clinical trials of the same drug (but for different indications) that had the effect of making the drug appear efficacious when it likely was not. Furthermore, the manipulation was concealed. The published research articles did not completely describe what the intended primary efficacy outcome variables were, did not provide results in terms of these variables, and instead provided results only in terms of variables that were chosen post-hoc as new primary outcome variables.

To address that latter point, I independently reviewed three of the research publications cited by Vedula et al.(2,3,4) All three were noted to have reported significant results favoring gabapentin in terms of a primary efficacy outcome variable that was not identified as such in the corresponding studies' original research protocols or reports (see the supplementary data provided with the New England Journal article.) Per my review, none of the three published articles offered any hint that what they reported as primary outcome variables were not the variables originally chosen in that capacity, nor did they identify what those original primary outcome variables were, or how comparisons made using them turned out.

The implications of the article by Vedula et al are very important. Hence, I was surprised that the article appeared without an accompanying editorial to discuss these implications, and that its publication did not generate much media interest.

So that gives me an opportunity to comment further.

One could start with the implications for evidence-based medicine. As noted above, a short description of the evidence-based medicine is medicine whose practice is informed by critical, rigorous review of the best available evidence from clinical research as revealed by systematic search of the published research literature, as well as by the clinician's understanding of biology and the medical and biopsychosocial context, and by the patient's own values. Evidence-based medicine depends on critical, rigorous review, but the review process is generally done under the assumptions that research publications honestly describe what was done and what its results were. The review process was never designed to detect dishonest reporting or find information that was deliberately concealed. Manipulation of research (design, analysis, and implementation), concealment of that manipulation, and outright suppression of research threaten the foundations of evidence-based medicine. Yet the article by Vedula et al is part of a growing body of evidence that such manipulation, concealment and suppression are widespread, and done to serve vested interests, often commercial.

That is a huge problem for proponents of evidence-based medicine, but also for physicians who want their practices to be based on science, for patients who want their care to be based on science, and for all those in society who see the advancement of medical science as a way to improve peoples' lives.

As senior author Professor Kay Dickersin noted in an interview with Bloomberg "The trouble is, as a scientist, the publication has always been held up to me as the truth. It's the scientific record. What this study indicated is we can't believe that record."

Furthermore, to be a bit more concrete, most physicians, patients, and policy makers depend on what appears to be honest clinical research to make decisions about individual care and health policy. Deliberate and deceitful manipulation of clinical research to favor sponsors' products has likely lead to excessive use of and payments for drugs and devices that are less effective than advertised, if not useless or dangerous. Thus, it is likely that such manipulation is partially responsible for ever increasing health costs and poor health outcomes.

Finally, we need to start thinking about how we can detect and compensate for manipulation of clinical research in the past, and deter such manipulation in the future. One possible deterrent would be, as was noted by Vedula et al, detailed clinical trials registries that contain complete information about trial protocols.  For this to be effective, there need to be mechanisms to assure compliance, and penalties for non-compliance.  Moreover, since clinical research is now global, the registries must have global scope, and enforced assurance of compliance must also be global.

Registries might decrease future manipulation and suppression of research.   No one has suggested, as far as I know, a systematic way to detect and correct for previous manipulation. It would require a major, global investigative effort to uncover manipulation, and it would be a major scientific and policy endeavor to reveal most suppressed research and correct most manipulations.

However, before anything is done, patients, physicians and policy makers must acknowledge and understand the problem.  Yet it seems that even discussing these may be topics that are very uncomfortable for some of us. The longer we shrink from addressing them, however, the worse will be the results for patients, physicians, science and society.

References


1. Vedula SS, Bero L, Scherer RW, Dickersin K. Outcome reporting in industry-sponsored tirals of gabapentin for off-label use. N Engl J Med 2009; 361: 1963-1971. Link here.


2. Mathew NT, Rapoport A, Saper J et al. Efficacy of gabapentin in migraine prophylaxis. Headache 2001; 41: 119-128. Link here.


3. Vieta E, Goikolea JM, Martinea-Aran A et al. A double-blind, randomized, placebo-controlled, prophylaxis study of adjunctive gabapentin for bipolar disorder. J Clin Psychiatr 2006; 67: 473-477.  Link here.


4. Caraceni A, Zecca E, Bonezzi C et al. Gabapentin for neuropathic cancer pain: a randomized controlled trial from the gabapentin cancer pain study group. J Clin Oncol 2004; 22: 2909-2917. Link here.