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Vigabatrin

Vigabatrin is an anticonvulsant that inhibits the catabolism of GABA. It is an analog of GABA, but it is not a receptor agonist. more...

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Mechanism of action

Vigabatrin is an irreversible inhibitor of gamma-aminobutyric acid transaminase (GABA-T), the enzyme responsible for the catabolism of GABA, which increases the level of GABA in the synapses.

Vigabatrin is a racemic compound, and its -enantiomer is pharmacologically active.,

Pharmacokinetics

With most drugs, elimination half-life is a useful predictor of dosing schedules and the time needed to reach steady state concentrations. In the case of vigabatrin, however, it has been found that the half-life of biologic activity is far longer than the elimination half-life.

For vigabatrin, there is no range of target concentrations because researchers found no difference between the serum concentration levels of responders and those of non-responders. Instead, the duration of action is believed to be more a function of the GABA-T resynthesis rate; levels of GABA-T do not usually return to their normal state until six days after stopping the medication.

Uses

Approved/clinically proven

Canada

In Canada, vigabatrin is approved for use as an adjunctive treatment (with other drugs) in treatment resistant epilepsy,complex partial seizures, secondary generalized seizures, and for monotherapy use in infantile spasms in West syndrome.

Mexico

As of 2003, vigabatrin is approved in Mexico for the treatment of epilepsy that is not satisfactorily controlled by conventional therapy (adjunctive or monotherapy) or in recently diagnosed patients who have not tried other agents (monotherapy).

Vigabatrin is also indicated for monotherapy use in secondarily generalized tonic-clonic seizures, partial seizures, and in infantile spasms due to West syndrome.

Unapproved/Investigational

In November of 2001, a team of scientists lead by Peter Zwanzger of the University of Munich reported that vigabatrin reduced cholecystokinin tetrapeptide-induced symptoms of panic disorder, in addition to elevated cortisol and ACTH levels, in healthy volunteers.

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Strange Bedfellows--chiropractic and vigabatrin
From Dynamic Chiropractic, 9/12/01 by Gorman, R F

The Great Australian Medical Scientific Fraud

Most chiropractors may not be aware of the drug Vigabatrin, much less its importance to the future of chiropractic. This is because medicine and chiropractic parallel, with little exchange of information between the two disciplines: Few chiropractors attend medical seminars, and few physicians attend chiropractic conferences. For more than 100 years, this arrangement has worked satisfactorily, but in the last decade, the agencies that fund health care are demanding evidence of the efficacy of spinal manipulation treatments. Evidencebased health care has been what orthodox medicine does well, and now chiropractic is expected to conform to the principles of scientific method in validating the efficacy of its procedures.

This change in expectation has caused problems for chiropractic, in that the discipline is not really sure what it does. Chiropractors generally manipulate spines for orthopedic problems, such as sore and stiff joints. But some believe that spinal manipulation has effects far beyond the spine itself: that spinal manipulation changes neurological function, and by so doing, allows the body to use innate resources to heal general bodily ills.

It is this expanded view of the role of chiropractic that is opposed by the medical establishment, which says, "Prove your point by scientific method or desist from making such claims." According to the evidence brought forward in Wilk, et al, v. the AMA et al., the medical establishment actively denigrated chiropractic to AMA members, and intimated that it was unethical to associate professionally with chiropractors.' The opinion of the court in this action was that the medical profession acted unreasonably and unjustly in its campaign against chiropractic. .

The Great Australian Medical

Scientific Fraud

In recent times, the medical profession has acted unconscionably in its efforts to suppress the value of chiropractic, both in the eyes of its members and in the opinion of the public. In the late 1970s, two medical practitioners, Dr. Eric Milne and myself, working in Mt. Isa, Queensland, Australia, discovered that a type of visual field loss was associated with spinal derangement. The type of visual field loss in question was concentric constriction of the visual fields. Further, we found that the field loss was relatively common in patients who had suffered spinal injuries. We showed that the visual abnormality recovered immediately when the spine was manipulated in a nonspecific way while the patient was anesthetized and relaxed by muscle-- end-plate depolarizing drugs.2-4

Recently, chiropractor Danny Stephens and associates joined with me in showing that the recovery of vision also occurred with outpatient chiropractic adjustments, but that the recovery was much slower than when anesthesia was used.5

For ease of description, I call the phenomenon the tunnel vision information (TVI), which states that vision improves in appropriate patients when the spine is manipulated. The importance of this discovery to chiropractic has been underestimated by the profession, in that the information has been known for more than two decades, yet there has been little effort by the chiropractic fraternity to bring the knowledge to the attention of the public, or to study it for what it is worth.

The unconscionable conduct of the Australian medical profession in regard to the TVI is chronicled by the records of the hounding of this author in medical regulatory courts in Australia, and in repeated instances of dishonest advice given to the Australian government by medical authorities about the recovery of vision with spinal manipulation.

I have given the medical profession in Australia more than ample opportunity to put its house in order by acknowledging the TVI. It was some nine to 10 years after the initial discovery was made, and after many public displays of the efficacy of spinal manipulation in curing visual field loss, that frustration was vented at the scientific intransigence of my medical colleagues by demonstrating the phenomenon in real time on the Australian "60 Minutes" program. In its segment, "A Dangerous Twist," two juvenile patients, a girl and a boy, were treated for constricted visual fields by spinal manipulation.6 Both patients had been referred to me on the same day by their respective optometrists. I felt that the occasion was auspicious enough to warrant a public demonstration. The arrangement with the "60 Minutes" program was that the patients would attend the University of New South Wales' department of optometry for confirmation of the visual field loss, and be reviewed there again after the procedure. This was done, and on review at the university some days after the procedure, the visual fields were normal, confirming the findings which were apparent to those present in the operating suite, immediately after the spinal manipulations.

Unfortunately, the chiropractic fraternity in Australia did not appreciate the value of the discovery and acted to disassociate itself from the phenomenon.' At this point, the "great Australian medical scientific fraud," as I have termed it, took on measurable proportions.

In a video film presentation to all the embassies of the United Nations in New York, I accused the Australian government and the scientific fraternity of running an immense scam.'

Prior to this, the various previous attempts to bring the tunnel-vision phenomenon to the Australian scientific community's attention were rebuffed: various scientific articles were refused publication and personal entreaties were snubbed.9

60 Minutes"'A Dangerous Twist"

When the program went to air on June 22, 1986, the presenter, Jeff McMullen, a longtime "60 Minutes" personality and an accomplished journalist, took a negative viewpoint of the value of the discovery and accentuated the dangers of spinal manipulation therapy, assisted by a senior Sydney chiropractor, who was co-opted onto the program.

The obvious benefit to the two patients, namely that their vision had been returned to normal, was acknowledged on the program, but was discounted. The spokesperson for the university implied that she thought the treatment was a form of quackery and that the recovery was a placebo response.

Medical Fraud by Conviction

In 1998, I was brought before the medical regulatory courts and convicted of professional misconduct, for demonstrating the recovery of vision that occurs when the spine is manipulated in appropriate patients." This conviction stands.

The Vigabatrin Saga

The trouble with attempting to suppress an intrinsic truth by legal or other means is that it will reappear sooner or later. In this case, the TVI has reappeared again in relation to the treatment of epilepsy. Vigabatrin, or Sabril, as it is called commercially, is a selective inhibitor of GABA (gamma aminobutyric acid) transaminase, an inhibitory neurotransmitter in the central nervous system and in the retina. Vigabatrin is indicated for epilepsy that is not adequately controlled by other methods.

Vigabatrin has been in use for about a decade, but an unexpected complication become apparent. On average, 30 percent of the patients using the drug develop irreversible contraction of the visual fields. Further, other anti-epileptic drugs are noted to be associated with visual field loss, for example, carbamazapine. 11-15

Constricted Visual Fields

in Vigabatrin Therapy

and in Chiropractic Therapy

Here is a situation where a feature of a neurological illness, namely constricted visual fields, is immediately resolved by chiropractic. What does this situation do for chiropractic? For one thing, it is a very comfortable state of affairs. For more than one hundred years, chiropractors have been protesting that they provided a therapy that was immensely beneficial, but their exhortations for community acceptance of their treatments have been consistently opposed by the medical profession on the grounds that there was no scientific validation of their efficacy. Now the shoe is on the other foot, and it is the medical profession and the drug companies that are faced with the task of investigating chiropractic for its value. Chiropractic and the community can sit back as interested and amused observers, as the medical profession wrestles with the problem posed by the appearance of constricted visual fields with Vigabatrin therapy.

The medical profession prides itself on its adherence to scientific discipline. Once a controlled trial shows that a particular therapy is ineffectual, the trial is stopped and the therapy discontinued. This dedication to the shrine of scientific method went horribly astray with regard to the recovery of vision with spinal manipulation. The evidence is very clear that spinal manipulation will resolve this defect in almost 100 percent of a particular subset of patients with constricted visual fields.2-6,16-24 Presumably, because of its pro-chiropractic implications, the medical profession has tried to suppress this knowledge by studiously ignoring it and convicting its prime protagonist - me - of professional misconduct, for my nonconforming convictions based on personal experience, which have had little precedent in medical history.

The researchers into the constricted visual fields caused by Vigabatrin cannot just leave the spinal manipulation subset of patients out of their calculations; it is totally unscientific to do so. It is not even reasonable to leave out the hysterical amblyopia cohort. Prior to the advent of the chiropractic series, constricted visual fields were regarded as a feature of psychoneurotic illness and called "hysterical amblyopia."25,26 However, as an aside, my associates and I regard the psychoneurotic group of patients with constricted visual fields the same as the group which responds to spinal manipulation; in addition, we make the point that if one aspect of psychoneurosis responds to spinal manipulation, the question of what happens to the other manifestations of hysteria, when the spine is adequately treated, should be investigated.

The scientific challenge - Does spi

nal manipulation resolve visual field loss

apparently due to Vigabatrin in some,

none, or all cases?

What the medical researchers dealing with the constricted visual field loss of Vigabatrin therapy must do is to define the participation of the "chiropractic" variant of this clinical state in the overall picture of the pathophysiology. The first (and medically and politically unpalatable) step is to acknowledge that the condition of constricted visual fields does resolve with spinal manipulation in some cases. Then they have a problem with the author of this article: What apology must be made to him before the research can proceed in a dignified manner? Worse also, they have to acknowledge that spinal manipulation might have a legitimate and possibly significant role in neurology.

It may be that the constricted visual fields that respond to spinal manipulation are a totally separate entity to those that occur in the case of Vigabatrin therapy. The simple way to discriminate between the two groups will be to challenge the patients of the Vigabatrin group by spinal manipulation.

Possibly, the Vigabatrin variety will not improve with spinal treatment; then further investigation can proceed logically, without the glaring deficiency in logic associated with the present medical observations in regard to the Vigabatrin group of patients. More interesting would be the appearance of some relationship between GABA involvement in the nervous system and the symptomatology and cerebral hypoperfusion seen in "whiplash" injury. Such a relationship could be contemplated if Vigabatrin does produce the visual field loss directly; and the cases encountered in the Vigabatrin group are not merely ambient examples of constricted visual fields, who have not been recognised as such, and who have been prescribed Vigabatrin.

To return to medicine and politics, in making this challenge, the medical researchers are forced to acknowledge the chiropractic cohort, and to commence cogitation of its dimensions, as should have been done in the years since 1986, when the phenomenon was demonstrated on the "60 Minutes" program in Australia.

The problem distracts the chiropractic profession from taking advantage of the Vigabatrin situation. There is failure on the part of chiropractors to discover patients with constricted visual fields in their practices. My chiropractic colleague Danny Stephens and I were able to find some 17 patients with constricted visual fields, gleaned from our respective practices over two to three years. The number of such patients worldwide passing undetected through chiropractic hands each year must number in the thousands.

Wall Perimetry

No special equipment is needed to find these patients. There's a simple test to elicit constriction of the visual fields. The patient sits facing the corner of a room and the examiner projects a light on the wall at 90 degrees to the line of the patient's gaze on either side. The patient should see the light easily in that position. If the light is not seen at the 90-degree angle, the light is brought forward on the wall until it is seen. The degree of constriction can be estimated with respect to a normal control subject sitting at the same distance from the corner. This test is called "wall perimetry,"27 and can be a very sensitive test if the examiner projects a smaller or dimmer target. However, usually a sharply defined, large, bright target is advised, as its use will obviate false-positive results.

In looking for patients with constricted visual fields, it is practical to be aware of the symptoms that suggest contraction of vision are present. Patients with severe headaches; dizziness; blurred vision; memory loss; mental dullness; and chronic tiredness, are much more likely to have constricted visual fields than patients without these symptoms. The greater the evidence, in the patient's history, of symptoms suggesting cerebrovascular hypoperfusion,11-1 the greater the likelihood that the visual fields will be constricted.

Conclusion

Irrespective of the outcome, the behavior of the medical scientists in the next few years as they deal with the Vigabatrin quandary will provide amusement and passive entertainment for the chiropractic profession; at the same time, it will mean potentially immense benefits to the community when the true value of spinal manipulation to health of humanity is acknowledged.

References

1. Getzendaner S. (US District Judge, Northern District of Illinois, Eastem Division). Memorandum, Opinion, and Order. Wilk, et al., v. American Medical Association, et al., August 27, 1987.

2. Langford-Wilson A. New view of tunnel vision. The Star, Mt. Isa, September 14, 1982

3. Howarth J. Claims of answer to vision scourge. The NX News, Darwin, November 13th, 1982, p 17.

4. Light at the end of the tunnel. The Melbourne Herald. Nov 10th; 1984: p 13.

5. Stephens D, Mealing D, Pollard H, Thompson P, Bilton D, Gorman RF. Treatment of visual field loss by spinal manipulation: A report on 17 patients. JNMS 1998:6(2) pp 53-66.

6. Morrison J. "A Dangerous Twist." TCN Channel 9 "60 Minutes" NSW, 22 June 1986.

7. The chiropractic profession commends "60 Minutes" for exposing "gross spinal manipulation." The West Australian Newspaper; Saturday, June 28th, 1986, p 21.

8. Gorman RE "The World and the Great Australian Medical Scientific Fraud." 25-minute video production, February 2000. Copies can be obtained from the author.

9. Bilton D, Stephens D, Gorman RF Tunnel vision information: a paradox of ethics economics, politics and science. J Manipulative Physiol Ther 1998:21(7), pp 468-78.

10. Mcintosh P. Limits placed on spinal treatment. Dr. Weekly 1990, June 1.

11. Eke T, Talbot JF, Lawden MC. Severe persistant visual field constriction associated with Vigabatrin. BMJ 1997:314, pp. 180-1.

12. Schmitz B, Jokiel B, Schmidt TK, et al. Visual field defects under treatment with Vigabatrin, carbamazepine and valproate; a prospective study. Epilepsia 1999:40 (Suppl. 2.) p 257.

13. Kalvianinen R, Nousianen I, Mantjyarvi M, Riekkinen Sr. P. Absence of concentric visual field defects in patients with initial tiagabine monotherapy. Epilepsia 1999:40 (Suppl.2.) p. 259.

14. Lawden MC, Eke T, Degg C, et al. Visual field constriction associated with Vigabatrin treatment. Epilepsia 1999:40 (Suppl.2.) p 257.

15. Update on visual field constriction with Vigabatrin. Aust Adv Drug Reactions Bull 1999:18(3).

16. von Kurbel F (Gorman RF). `Chiropractic Medicine.' Academy of Chiropractic Medicine, Darwin, NT, Australia 1984. (Reports 25 patients successfully treated - Copies can be obtained from the author.)

17. Gorman RF. The treatment of visual perception defect by spinal manipulation: a prospective peer-reviewed study of 12 consecutive patients. 24th Annual Scientific Congress of the Royal Australian College of Ophthalmologists. Sydney, Nov 1-6, 1992.

18. Gorman RF. Computerised static perimetry in chiropractic. J Manipulative Physiol Ther 1993:16, pp 481-487.

19. Gorman RF. Monocular visual loss after closed head trauma; with immediate resolution associated with spinal manipulation. JMPT 1995:18(5), pp 308-14.

20. Stephens D, Gorman RE Does 'normal' vision improve with spinal manipulation? J. Manipulative and Physiol Therapeutics 1996:19(6), pp 415-8.

21. Stephens D, Gorman R. The prospective treatment of visual perception deficit by chiropractic spinal manipulation: a report on two juvenile patients. Chiropr J Aust 1996:26(3), pp 8288.

22. Stephens D, Gorman F, Bilton D. The step phenomenon in the recovery of vision with spinal manipulation: A report on two 13-yr-olds treated together. J Manipulative Physiol Ther 1997:20(6) pp 28-33.

23. Stephens D, Gorman F. The association between visual incompetence and spinal derangement: an instructive case history. J Manipulative Physiol Ther 1997:20(5), pp 343-50.

24. Gorman RF, Anderson RL, Bilton D, Favoloro RJ Pittorino AJ. Case report: Spinal strain and visual perception deficit. Chiropr JAust 1994:24, pp 131-4.

25. Yasuna ER. Hysterical amblyopia in children. Amer J Dis Children 1963: 106, pp 68-73.

26. Cogan DC. Neurology of the Visual System. Charles C. Thomas, Springfield, Illinois, 1966; 310.

27. Stephens D, Bilton D. Pollard H, Gorman F. Wall perimetry in chiropractic. J Manipulative Physiol Ther 1998:21, pp 32-36.

28. Otte A, Mueller-Brand J, Fierz L. Brain SPECT findings in late whiplash syndrome. Lancet 1995:345, pp 1513-14.

29. Otte A, Thierry E, Fierz L, Mueller-Brand J. Parieto-occipital hypoperfusion in late whiplash syndrome: First quantitative SPET study using technetium-99m biscisate (ECD). Eur J Nucl Med 1996:23, pp 72-74.

30. Otte A, Ettlin TM, Mueller Brand J. Comparison of 99m Tcv-ECD with

99m Tc-HMPAO-brain-SPECT in late whiplash syndrome. Journal of Vascular Investigation 1995:1(4), pp 157-163.

RF Gorman,MBBS,DO,FRACO

Queensland

Australia

Copyright Dynamic Chiropractic Sep 12, 2001
Provided by ProQuest Information and Learning Company. All rights Reserved

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