Term Paper: Ritalin: The Case History

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[. . .] However, because of the presence of two stereogenic centers in methylphenidate, this process proved to be challenging. A variety of experiments led eventually to an overall yield of 40% threo-methylphenidate hydrochloride with an excellent degree of enantiomeric purity. (Prashad, 2001)

Novartis also explored the possibility of enzyme-based resolution, but encountered difficulty in suppressing the erythro racemate. (Prashad, 2001)

Jeffrey Winkler and his research group achieved a breakthrough in 1999, using an enantioselective synthesis approach. Starting from achiral materials, this process was able to synthesize chiral Ritalin, using only the biologically active "right hand" of the compound. The implications of this discovery are far-reaching. The new product, which would be an analogue of the original Ritalin, would have the psychostimulant effect on the dopamine receptors necessary for control of ADHD symptoms, but would require a smaller dose in order to accomplish its task. Undesirable side effects could be minimized. At the same time, the new analogue may be able, with a ten-to-one selectivity rating, to block the effect of cocaine in the brain. (American Chemical Society press release, 1999) Thus, it could be used in anti-cocaine therapy (in a way similar to Natrexone for anti-Vicodin/opiate cravings). (Vicodin hotline)

The ADHD-treatment form of the new drug is in production; however, the cocaine-receptor antagonist analogue is still undergoing research. (Warner Lambert Lectureship notes, 2000)

Winkler has utilized some of Doyle's research (Colacot, 2000) to produce a relatively inexpensive, yet pure enantioselective analogue with exciting possibilities. (Axten et al., 1999)

From a purely business standpoint, there is a benefit to be derived in exploring the possibilities of developing chiral drugs with single-enantiomer dosage forms. Between 1999 and 2000, sales of drugs in this format increased market share from one-third to 40%. From the viewpoint of the public and the prescribing physician, the virtue of the chiral drugs is the reduction of side effects. From the viewpoint of the maunfacturer, the development of a chemically distinct form enables them to acquire a new patent. By utilizing racemic switches, redeveloping racemic mixtures as single enantiomers, companies can prolong patent life. Chirotechnology firms such as Celgene carry out racemic switches on the drugs of other firms and then license the patent back to the original developer, sell it to a third party or market the new analogue themselves. (Stinson, 2001)

Novartis' 1950 patent on the original Ritalin has expired some time ago. They have taken a license on Celgene's patent on (R, R)-methylphenidate, the active enantiomer of Ritalin, as of April 2000. Celgene has also sold the patent's Canadian rights to Biovail, an Ontario-based pharmaceuticals firm. (Stinson, 2001) competitor to both Novartis and Celgene is Alza Pharmaceuticals, a California-based company marketing controlled-release racemic methylphenidate pill called Concerta, and approved by the FDA in August 2000. Alza's so-called Oros technology has allowed them to counter the tolerance-building property of methylphenidate by building in an osmotic gradient under the outer layer of the tablet. As the outer layer encounters water, the next layer, the so-called "push" layer expands, forcing medication out the hole in the tip of the tablet. Medication is also contained in the outer layer itself. Thus, the patient receives immediate medication, followed by the slower release of the inner part of the tablet, in differing concentrations. The drug can be administered three times a day, and timed so as to not interfere with either eating or sleeping. (Henry, 2000)

It should be stated that not all treatment for ADHD needs to be methylphenidate-based. Some studies have supported parent and classroom measures which would attempt to mediate the symptoms purely on a psychosocial basis. (Pelham, Wheeler, and Chronis, 1998) The use of tricyclic anti-depressants has been studied in more than one thousand patients, along with other studies of alternative antidepressants, antipsychotics and antihypertensives. (Spencer et al., 1996) A nonstimulant agent, bupropion, is being studied as a possible treatment for both adults and children with ADHD. (Cantwell, 1998) Guanfacine and clonidine have been tested on ADHD subjects and have shown promising results. (Hunt, Arnsten and Asbell, 1995)

The future of Ritalin appears promising, however, in spite of the reservations that have already been cited. The new analogues developed by Winkler et al. would appear to circumvent some of the problematical aspects of the early version of the drug, both for prescribed users and illicit drug users. Studies that support the use of Ritalin in conjunction with psychosocial supports appear to offer the most hope for a long-term amelioration of ADHD symptoms, and a possibility of achieving a relatively normal lifestyle for those suffering from the disorder.

Works Cited

American Chemical Society press release, March 22, 1999. "Improved Ritalin offers smaller doses and fewer side effects." [Online]. Retrieved January 11, 2003 at http://www.hypsos.ch/presse/improvedmph.htm

Attention Deficit Disorder Help Center. "Ritalin effects and ADD ADHD medicine side effects." [Online]. Retrieved January 4, 2003 at http://www.add-adhd-help-center.com/ritalin_side_effects.htm

Cantwell, D.P. "ADHD through the life span: the role of buproprion in treatment." J. Clin Psychiatry 1998; 59 Suppl 4: 92-4.

Colacot, T.J. "An overview on the applications of Doyle catalysts in asymmetric cyclopropanation and CH insertion reactions," Proc. Indian Acad. Sci. (Chem. Sci.) June 2000. Vol. 112, No. 3: 197-207.

DEA press release. "Methylphenidate." October 20, 1995. [Online]. Retrieved January 23, 2003 at http://web1.caryacademy.org/chemistry/rushin/StudentProjects/CompoundWebSites/2000/R

Goldman, L.S.; Genel, M.; Bezman, R.J.; Slanetz, P.J. "Diagnosis and treatment of attention deficit hyperactivity disorder in children and adolescents." JAMA 1998 Apr 8; 279(14): 1100-7.

Greener, M.J. "Drug delivery and reformulation technologies: prospects for single-isomer therapeutics." Decision Resources Inc., May 30, 2001. [Online]. Retrieved January 4, 2003 at http://cisti-icist.nrc-cnrc.gc.ca/zone/cisti/dresources/decision/01/01h701/01h701.pdf

Henry, C. "Engineering a new drug delivery profile." Chemical and Engineering News. Sept. 18, 2000, Vol. 78, No. 38: 49-65.

Hunt, R.D.; Arnsten, A.F.; Asbell, M.D. "An open trial of guanfacine in the treatment of attention deficit hyperactivity disorder." J. Am Acad Child Adolesc Psychiatry 1995 Jan; 34(1): 50-4.

Hyman, S.E. "Statement for the record on methylphenidate (Ritalin) for children with ADHD," May 16, 2000. [Online]. Retrieved January 10, 2003 at http://www.hhs.gov/asl/testify/t000516c.html

Klein, R.G.; Mannuzza, S. "Hyperactive boys almost grown up." Arch Gen Psychiatry 1988 Dec; 45(12): 1131-4.

National Vicodin hotline. [Online]. Retrieved January 11, 2003 at http://www.nationalhotline.org/vicodin-cont.html

Novartis Pharmaceuticals Corporation. "Ritalin hydrochloride." January 2001. T2001-08; 89002403.

Pelham, W.E. Jr.; Wheeler, T.; Chronis, A. "Empirically supported psychosocial treatments for attention deficit hyperactivity disorder." J. Clin Child Psychol 1998 Jun; 27(2): 190-205.

Prashad, M. "Approaches to the preparation of enantiomerically pure (2R,2'R)-(+)-threo-methylphenidate hydrochloride." Novartis Institute Research, April 20, 2001. [Online]. Retrieved January 15, 2003 at http://www.rhodium.ws/pdf/threo-methylphenidate.pdf

Spencer, T.; Biederman, J.; Wilens, T.; Harding, M.; O'Donnell, D.; Griffin, S. "Pharmacotherapy of attention deficit hyperactivity disorder across the life cycle." J. Am Acad Child Adolesc Psychiatry 1996 Apr; 35(4): 409-32.

Stinson, S.C. "Chiral Pharmaceuticals," Chemical and Engineering News. Oct. 1, 2001, vol. 79, No. 40: 79-97.

Vincent, J.; Varley, C.K.; Leger, P. "Effects of methylphenidate on early adolescent growth." Am J. Psychiatry 1990 Apr; 147(4): 501-2.

Volkow, N.D.; Wang, G.J.; Fowler, J.S.; Gatley, S.J.; Logan, J.; Ding, Y.S.; Hitzemann, R.; Pappas, N. "Dopamine transporter occupancies in the human brain induced by therapeutic doses of oral methylphenidate." Am J. Psychiatry 1998 Oct; 155 (10): 1325-31.

Warner Lambert Lectureship Series notes, 2000. "Biographical Notes: Jeffrey Winkler." [Online]. Retrieved January 10, 2003 at… [END OF PREVIEW]

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