myparkinsons.co.uk

The History of Madopar

F O C U S O N P A R K I N S O N ’ S D I S E A S E
VOLUME 1 6 – SUP P L EMENT A – 2 0 0 4 A7
LEVODOPA
GUGGENHEIM
The levodopa story started 90 years ago, when Roche was a
young pharmaceutical company with a total of 145 employees.
The profits made with the main product – Sirolin®, cough
syrup, allowed a new plant to be built and more to be invested
in research. At this time, the company’s main objective of
research was to extract highly potent substances from plants
and other natural products. A young chemist was recruited,
Dr M. Guggenheim, whose main scientific interests were the
‘proteinogenic amines’. He therefore noticed with great interest
2 articles from Torquati2,3 describing the presence of a
nitrogen-containing substance in the seeds and green pods of
Windsor beans. Mr F. Hoffmann, the founder of the firm
Hoffmann-La Roche, was apparently fond of Windsor beans
and had a field planted with them which Guggenheim’s laboratory
overlooked. Guggenheim asked his boss if he could get
‘some beans’ and with his assistant picked 10 kg the next
morning.4 Rumour has it that Madame Hoffmann was not
amused. Guggenheim repeated and varied the extraction procedure
of Torquati to produce crystals and identified the isolated
substance as l-dioxyphenylalanine, levodopa.5 A patent
application was guaranteed a year later.
Levodopa was tested in animals (on the general behaviour
of conscious rabbits) and isolated organs (isolated rabbit
uterus and intestine). Guggenheim had hypothesized that
levodopa would be a precursor of adrenalin, but against all
expectations, the intravenous application of 20 mg levodopa
had no measurable effect on blood pressure or lung function in
the rabbits. Guggenheim decided therefore to test levodopa
himself. He took 2.5 g of levodopa per os: 10 minutes after
intake he felt terribly sick and vomited twice. He mentions in
the publication “that therefore not all the substance was
absorbed.”5 No other effects were observed.
Three years later, in 1916, Guggenheim caused a lab
explosion and lost eyesight completely, but from 1918 onward
he continued his work as a research director at Roche. With
the help of his secretary, Mrs I. Schramm (for many years
THE HISTORY OF MADOPAR
Roman Amrein, MD
L a n d h a u s w e g 3 1 , 4 1 2 6 B e t t i n g e n , S w i t z e r l a n d
SUMMARY
Madopar® – a combination of levodopa with the decarboxylase
inhibitor (DCI) benserazide – was first introduced 30 years ago
during July 1973, a few months earlier than the second
levodopa/decarboxylase-inhibitor combination – Sinemet®.
These 2 preparations have revolutionized the treatment of
Parkinson’s disease (PD) and are still considered to be the gold
standard for its treatment.1 The constituents of Madopar®
resulted from long-lasting systematic basic research, but the
idea to combine the 2 components was based on a working
hypothesis with inaccurate prerequisites. Intense systematic
basic and clinical research, excellent clinical observation,
openness for the unforeseen, serendipity, and fortune are all
present in the pedigree of Madopar®.
KEYWORDS: MADOPAR – LEVODOPA
Figure 1. Sirolin 1920.
F O C U S O N P A R K I N S O N ’ S D I S E A S E
A8 VOLUME 16 – SUPPLEMENT A – 2004
she was reading him all
scientific publications)
he published the material
he had collected in
the field of biogenic
amines in a book which
was published in 1920.6
In the meantime, his
group had improved the
manufacturing process
for levodopa, and the
substance was sold for
scientific investigations.
However, the importance of the discovery was not evident at
that time: Guggenheim mentions levodopa in the 376 pages of
his book only with 2 sentences. During the following years at
Roche, levodopa was tested in additional animal models, as
well as for antibacterial properties, but without success.
Guggenheim continued his interest in biogenic amines as
documented by the subsequent editions of his book,7,8 but
levodopa was still an orphan drug without an indication when
he retired in 1948.
BIRKMAYER AND HORNYKIEWICZ
Walther Birkmayer qualified in medicine in 1935 and afterwards
specialized in neurology and psychiatry up to 1939.
During the Second World War, he was first an army physician
in Russia and then was transferred to Vienna, Austria, as chief
physician of an army hospital for patients with head injuries.
He treated over 3,000 patients and described his observations
in a book. After the war, he was eager to continue his scientific
work, but since this was difficult at the time, he accepted a
post in charge of the neurological ward of the Municipal
Home for the Aged in Lainz (Vienna) to take care of resident
patients with PD, multiple sclerosis (MS), or following
strokes.9 His medical activity in Lainz was mainly charitable,
and medical research was limited to reading, clinical observation,
and dissection.
Birkmayer stored
dozens of brains of
deceased PD, MS, and
post-stroke patients. In
1957, he contacted
Hornykiewicz at the
Institute for Experimental
Pathology in
Vienna and suggested
he analysed neurotransmitters
in the brains of
deceased parkinsonian
patients. Hornykiewicz
showed no interest and
refused for lack of time,9 but his interest became intense in
January 1959 after the publications of Bertler and Rosengren,
who reported the localization of dopamine in the basal ganglia
of the dog;10 the publication of Carlsson et al. on the presence
of 3-hydroxytyramine in the brain;11 and the publication of
Sano et al.,12 showing that in the human brain most of the
dopamine is concentrated in the basal ganglia. Prof. Brücke,
the head of Hornykiewicz’s Institute, contacted Birkmayer to
get permission to analyse the brains of deceased parkinsonian
patients that Birkmayer had stored. An agreement was made
that all future results from this would be published together.
The analytical work of Hornykiewicz was very successful, and
with his ‘collaborator in training’, Herbert Ehringer, he published
the results 1 year later.13 Birkmayer was very angry
when he realized that he was not a co-author of this publication
and was determined to get his revenge. In January 1961,
Hornykiewicz asked Birkmayer to try out levodopa in his resident
PD patients. He provided him with 2 g of levodopa
donated for in vitro studies by A. Pletscher, medical director
at Hoffmann-La Roche, and suggested that this should be
administered intravenously. Birkmayer accepted but delayed
beginning the study by at least 6 months. Ten years later he
wrote in a letter to Hornykiewicz: “Da du mich damals so
abfahren liessest, habe ich mich mit der sechsmonatigen
Blockade deiner Dopatherapie gerächt” (Because at that time
you had turned me down so bluntly, I took revenge on you by
blocking for 6 months your levodopa therapy).14
During the summer of 1961, 20 patients suffering from
post-encephalitic parkinsonism or PD received single intravenous
doses of levodopa (50–150 mg). An impressive reduction
of their akinesia was seen a few minutes after injection,
and this effect lasted for several hours. Results were documented
in a film.
Birkmayer visited Roche in Basle on 26 October 1961
and reported the results that he had seen after the injection of
levodopa, and showed his film. Birkmayer’s results were so
spectacular that they were difficult to believe: he described
Figure 2. M. Guggenheim.
Figure 3. W. Birkmayer.
Figure 4. H. Ehringer and O. Hornykiewicz.
F O C U S O N P A R K I N S O N ’ S D I S E A S E
VOLUME 1 6 – SUP P L EMENT A – 2 0 0 4 A9
and demonstrated patients with intense akinesia who had
been bedridden for several months or even years. After a
single intravenous injection of levodopa, the akinesia disappeared
to a large extent, and the patients could get up and
walk around the room.15 Was this the action of levodopa after
transformation to dopamine, was this a placebo effect induced
by a charismatic and enthusiastic doctor, or was this just
trickery?
Birkmayer had the impression that nobody believed him,
and he was right: there was a complete consensus within the
scientific community of Roche that the data shown by
Birkmayer were too good to be true.15 At least Birkmayer was
subsequently given the quantity of levodopa needed for additional
work, and some scientific collaboration with Roche was
initiated. Together with Hornykiewicz, he gave the same
lecture as at Roche at the monthly scientific session of
Vienna’s Medical Society on 10 November 196116 and published
the study the same day.17
In addition to the data presented in Basle, it was shown
that co-medication with a monoamine oxidase (MAO)
inhibitor intensifies and prolongs the effect of levodopa.
Overall, the results were well accepted, especially since
F. Gerstenbrand from the Neurological University Clinic in
Vienna confirmed them based on his own very recent experience.
However, Prof. H. Hoff, a famous neurologist, warned
against therapeutic over-optimism since levodopa treatment
would, in his mind, alleviate some of the parkinsonian symptoms
for a time, but the patients would still suffer from PD.
BARBEAU
In the same year, Barbeau in Canada published that patients
with PD excrete dopamine in the urine in much lower quantities
compared with normal subjects.18 He repeated and expanded
the biochemical study in a total of thirty PD patients. To
clarify the biochemical findings, he gave them single oral doses
of levodopa (100 or 200 mg) alone or combined with an
MAO inhibitor or with methyldopa and compared the results
with those from single
applications of placebo,
methyldopa, and other
reference substances.
Methyldopa given alone
or in combination with
levodopa increased the
tremor, whereas levodopa
reduced the rigidity
to half. The levodopa
effect was increased and
prolonged by the application
of the MAO
inhibitor parnate, but
blood pressure increased
dramatically under this combination from 125/80 to 230/125.
The results were reported in part at the 7th International
Congress of Neurology in Rome, Italy, 10–15 September
1961,19 and in full a few days later at the Bel-Air symposium.20
All these publications stimulated an enormous interest in
the scientific community, and institutions all over the world
published their experience with levodopa. Overall, the results
were not really conclusive, with outcomes varying from
enthusiastic positive to completely negative. There were
several reasons for this. In the 1960s, it was difficult to obtain
levodopa since the basic material for synthesis was L-tyrosine
produced by hydrolytic decomposition of natural silk, fish
meal, casein, or maize gluten. It was also possible to synthesize
a racemic mixture of dopa directly from vanillin and hippuric
acid and then, using a complex procedure, to subsequently
isolate levodopa.21
In addition to Roche, very few companies produced levodopa,
and the investigators usually had only small quantities
available, sufficient only for single-dose experiments or for a
very small series of experiments. Hence, the doses used were
often much too small to show a reliable clinical effect, and the
number of patients investigated was usually very limited. In
addition, most of the papers simply confirmed a pharmacological
effect without offering a proper therapeutic approach. This
gap was filled in 1967 by the studies of George Cotzias in New
York, who increased the levodopa dosage in a stepwise way to
very high levels (up to 16 g per day). The results were dramatic
in 20 out of 28 patients. This was the beginning of levodopa
offering substantial symptomatic relief, but at the price of
frequent side-effects, mainly nausea and vomiting. The first
results presented at a congress were published in 1969.22,23
MADOPAR
PLETSCHER
In 1961, Dr Hegedüs in the basic-research department of
Hoffmann-La Roche prepared Ro 4-4602, a molecule chemically
related to α-methyldopa
(Aldomet®), for
clinical investigation.24
Known as benserazide,
this molecule was nearly
100 times more active as
a DCI than α-methyldopa
in vitro and in
vivo. It was therefore
hoped that benserazide
would behave as a strong
antihypertensive agent,
by inhibiting the formation
of endogenous cateFigure
5. A. Barbeau. cholamines, especially Figure 6. A. Pletscher.
F O C U S O N P A R K I N S O N ’ S D I S E A S E
A10 VOLUME 16 – SUPPLEMENT A – 2004
noradrenaline. In addition, the molecule was put forward for
investigation in anxious–depressed patients. Benserazide was
well tolerated, but no antihypertensive effect was found (even
at doses as high as 10 g/day) in the exploratory clinical programme,
in which also Professor Birkmayer administered it to a
few elderly patients.15 Pletscher suggested to Birkmayer that he
should give the inhibitor to PD patients simultaneously with
levodopa.
Pletscher’s hypothesis was that preventing the decarboxylation
of levodopa would inhibit the formation of dopamine and
thereby inhibit the therapeutic action of levodopa. This would
provide evidence for the proposed mechanism of action of
levodopa or suggest that Birkmayer’s previous levodopa results
were strongly influenced by placebo effects.4,15 When
Birkmayer visited Basle a few months later, the basic
researchers were surprised when he related an enhancement,
not an inhibition, of the levodopa effect. Prof. Pletscher did
not declare that Birkmayer was mad – as others did – ; instead,
he was prepared to reconsider his working hypothesis. A short
period of enormous scientific effort followed, resulting in the
insight that benserazide hardly penetrates the blood–brain barrier,
acting mainly in the periphery – in the intestine, the liver,
the heart, the capillaries of the brain, but not in its parenchyma.
25
After the intake of the combination, much more levodopa
is therefore available in the blood for transition into the brain,
since the peripheral formation of dopamine is reduced. The
most frequent side-effects seen after the intake of high levodopa
doses, nausea and vomiting, are attributable to high
dopamine concentrations in the periphery. The clinical observation
that the use of benserazide increases the efficacy of
levodopa, and decreases the severity and the incidence of the
side-effects, had found its rational explanation.
Figure 7 shows the inhibition of the decarboxylase enzyme
in heart and brain tissue of rats after intraperitoneal injection
of increasing doses of benserazide. The effect in the brain is
more than 10 times less pronounced than in the heart.
Birkmayer’s first reports26,27 on the results of his pilot study
with the benserazide/levodopa combination generated enormous
interest, but the transition from fascinating human pharmacology
to clinical trials, resulting in a new therapy, was long
and difficult.
For a short period, another DCI, Ro 8-1756, was clinically
tested to ensure that Ro 4-4602, found by serendipity for the
treatment of PD, was not only the first, but also the best DCI
that Roche had at its disposal. In a short time, the neurosurgeon
Siegfried et al. accumulated the results from treating
500 patients with one or the other inhibitor.28
Dose finding and selection of the optimal proportion of
levodopa/DCI were difficult, since at the time no consensus
had been reached on the optimal dosing regimen for levodopa
given alone. It was clear from the beginning that the new
treatment should be based on a fixed combination of the
2 components. The idea was to minimize the daily dose of
levodopa by significantly blocking the decarboxylase in the
periphery. Over time, clinicians were encouraged to use the
combination in a variety of ratios, and the following fixed
combinations were used: DCI:levodopa of 1:4; 2:3; 1:4; 1:1;
and 3:1. The publication by Cotzias et al. on the long-term
results of high-dose levodopa treatment23 was of the utmost
significance for the ongoing studies with the combinations,
since, prior to that, the plasma concentrations of levodopa
needed for the effective treatment of parkinsonism were not
known.
Roche was immediately confronted with a new problem:
it was imperative to find a way to make the synthesis of levodopa
more efficient and a simpler process, otherwise it would
not be possible to produce the large quantities needed at an
acceptable price. However, this was achieved by the efforts of
2 groups of chemists, who simplified the extraction of levodopa
from the racemic mixture.29,30
In 1979, it was felt that the clinical studies with the levodopa/
DCI combinations had developed sufficiently to take a
decision on the final steps for large-scale use of the combination
in patients with PD. The Fourth Symposium Bel-Air,
under the presidency of Prof. J. de Ajuriaguerra and Prof.
G. Gauthier, offered the opportunity to discuss the results
with levodopa and its combinations, in terms of basic research
and therapeutic potential.
Several contributions reported results with levodopa
alone, demonstrating the high long-term success rate of this
treatment, but also the high incidence of side-effects.
Birkmayer et al.,31 Siegfried,32 and Tissot and Gauthier33
reported the results of open studies with the levodopa/DCI
combination: an increased efficacy of various degrees, combined
with better tolerability. Barbeau performed the first
randomized comparative study in which doses were gradually
increased over time. A total of 800 mg levodopa/day given
together with daily doses of 150–200 mg benserazide, resulted
100
1 10
Heart Brain
100
80
60
40
20
0
Inhibition (%)
Dose of Ro 4–4602 (mg/kg)
Figure 7. Benserazide inhibition of levodopa decarboxylase
in heart and brain. (Bartholini G, et al.25).
F O C U S O N P A R K I N S O N ’ S D I S E A S E
VOLUME 1 6 – SUP P L EMENT A – 2 0 0 4 A11
in good or excellent improvement in 75% of patients, compared
with 65% in patients given daily doses of 4.3 g levodopa
alone. Treatment with the combination was accompanied by a
dramatic decrease in side-effects, namely nausea, bradykinesia,
hypotonia, and psychic disturbances.
The final presentations at the symposium were dedicated
to the toxicological findings in animal and man. The inhibitor
produced the usual insignificant changes in mice, rabbits, and
dogs, but in rats, severe skeletal deformities as a consequence
of stimulation of the periosteal mesenchyma were observed.
The pathogenesis of these skeletal changes was completely
unknown.34 However, extensive clinical monitoring of
patients who had received benserazide had not revealed any
toxic reactions.35 Nevertheless, the toxicological findings in
rats were a big problem, and pessimists predicted the end of
the programme.
Fortunately, the toxicologist in charge of the levodopa/
DCI combination (subsequently named Madopar®),
Dr Schärer, could give the all-clear 18 months later: he
showed that in rats, the growth zones of most bones are not
closed during adult life, in contrast to man, where all the epiphyseal
cartilage plates are ossified soon after puberty. Drugs
like benserazide, that cause alterations in these structures, can
therefore only react in humans until the end of puberty, compared
with during the entire life span in rats. “When alterations
of this kind are produced in older rats, no conclusions
can be drawn for adult humans, as old rats can only be compared
with growing humans as far as skeletal growth is concerned,”
Schärer reported.36 The contraindication ‘Madopar®
must not be given to patients less than 25 years old (skeletal
development must be complete)’ is based on these findings.
Fortunately, not one single case of skeletal deformities has
occurred in humans, although more than 1 million patients
have been treated with Madopar® for several years.
The multicentre studies with the fixed-combination ratios of
DCI:levodopa of 1:4 and 3:2 were performed with extreme
caution and with very frequent analysis, especially for any
changes in laboratory parameters. In the early 1970s, most
European case reports did not exceed 10–25 pages, but for the
Madopar® studies, it was not unusual for a patient record to
transcend 400 pages, with laboratory examinations being
carried out nearly every week. During the course of the studies,
it became clear that the 3:2 combination, containing the high
amount of inhibitor, did not offer any advantage. Hence, studies
with this ratio were no longer pursued.
In summer 1972, Roche started to compile the new drug
application (NDA) under the leadership of R. Dubuis and
J. Fischlewitz. The assistants B. Schonlau, H. Bastova and
M. Tock encoded the patient data together with a small group
of temporary engaged students, whereas M. Christeller and his
crew was responsible for entering the data on a total of more
than 200,000 80-column punch cards and for the subsequent
statistical evaluation of the data. Enthusiasm and working
overtime resulted in a first submission in January 1973.
The NDA contained study reports on 463 Madopar® cases,
1,059 cases with levodopa alone, and 154 cases with the
3:3 combination ratio, as well as 30 publications (including
the personal experience of the clinicians) on a total of more
than 1,000 other cases. On average, there was a reduction of
the parkinsonian symptoms of 30% within the first 2 weeks of
treatment. After 3 months of treatment, the sum of symptoms
on the Webster scale was reduced by a half. All symptoms did
improve, but rigidity, gait, self-care, and facial expression
showed greater improvement than tremor. Madopar® was first
introduced to the market in Switzerland during July 1973 and
shortly afterwards in more than 100 countries all over the
world.
The history of Madopar® is associated with 2 Nobel prizes.
The story started when Carlsson had identified dopamine as a
transmitter and had shown that animals suffering from reserpine-
induced pseudoparkinsonism can be successfully treated
with levodopa. For these discoveries he was awarded the
Nobel Prize for Physiology or Medicine in 2000.
At the time when Madopar® was being developed, Roche’s
synthesis of levodopa started with the production of a racemic
mix of dopa from vanillin and hippuric acid. Vanillin was
purchased in bulk from Monsanto. In the early 1960s,
W.S. Knowles from Monsanto was involved in an exploratory
programme with the aim of producing catalysts that provided
a high enantiomeric excess. By testing enantiomers of phosphines
with a varied structure, Knowles and his colleagues
quickly succeeded in producing catalysts (transition metals)
that allowed nearly 100% pure levodopa to be obtained at the
end of the hydrogenation reaction. This so-called asymmetric
hydrogenation or mirror-image catalysis resulted in a dramatic
improvement in the industrial production of levodopa, and
0
40
50
60
70
80
90
100
2 4 6
Week
Webster score, baseline (%)
8 10 12
Bradykinesia W1
Rigidity W2
Posture W3
Upper-extremity W4
Gait W5
Tremor W6
Facies W7
Seborrhoea W8
Speech W9
Self-care W10
Total score
Figure 8. Madopar® Webster score over time; NDA 1972
(n = 463).
F O C U S O N P A R K I N S O N ’ S D I S E A S E
A12 VOLUME 16 – SUPPLEMENT A – 2004
soluble hydrogenation catalysts started a new era in catalytic
processes. Asymmetric hydrogenation is now used in a number
of industrial syntheses of pharmaceutical products, such as
antibiotics, anti-inflammatory drugs, and heart medicines. In
recognition of this work, the Royal Swedish Academy of
Sciences awarded William S. Knowles the Nobel Prize for
Chemistry in 2001.37
Acknowledgement
I thank Prof. J. Birkmayer, son of Prof. W. Birkmayer, and the
librarians at Roche for their help to retrieve historical documents on
Madopar®, as well as a copy of Prof. W. Birkmayer’s film on one
of the first patients treated with L-dopa.
REFERENCES
1. Olanow CW. The role of dopamine agonists in the treatment of early Parkinson’s
disease. Neurology 2002;58 Suppl 1:S33-41.
2. Torquati T. Über die Gegenwart einer stickstoffhaltigen Substanz in den Keimlingen
von Vicia faba. Arch Pharmacol Sper 1913;15:213-23.
3. Torquati T. Über die Gegenwart einer stickstoffhaltigen Substanz in den grünen
Hülsen von Vicia faba. Arch Pharmacol Sper 1913;15:308-12.
4. Klingler M. Research into new treatments: past and future in Gordon Holmes
Centenary Symposium; 1976 Mar 1-4; London. Roche internal document; 1976. p. 10.
5. Guggenheim M. Dioxyphenylalanin, eine neue Aminosäure aus Vicia faba.
Hoppe-Seylers Hoppe Seylers Z Physiol Chem 1913;88:276-84.
6. Guggenheim M. Die biogenen Amine und ihre Bedeutung für die Physiologie und
Pathologie des pflanzlichen und tierischen Stoffwechsels. Monographien aus dem
Gesamtgebiet der Physiologie der Pflanzen und der Tiere. In: Czapek NF, Parnas J,
editors. Berlin: Verlag von Julius Springer; 1920. p. 1-376.
7. Guggenheim M. Die biogenen Amine und ihre Bedeutung für die Physiologie und
Pathologie des pflanzlichen und tierischen Stoffwechsels. 3rd edition. Basel: Karger;
1940. p. XVI, 564.
8. Guggenheim M. Die biogenen Amine und ihre Bedeutung für die Physdiologie und
Pathologie des pflanzlichen und tierischen Stoffwechsels. 4th edition. Basel: Karger;
1951. p. 619.
9. Birkmayer W. Madopar – Ratio und Fortuna, wie ich es erlebte, in L-dopa
Substitution der Parkinson-Krankheit. Umek PRaH, editor. New York: Springer-
Verlag; 1985. p. 145-50.
10. Bertler, A, Rosengren E. Occurrence and distribution of dopamine in brain and other
tissues. Experientia 1959;15:10-5.
11. Carlsson A, Lindqvist M, Magnusson T, et al. On the presence of 3-hydroxytyramine
in brain. Science 1958;127:471.
12. Sano I, Gamo T, Kakimoty Y, et al. Distribution of catechol compounds in human
brain. Biochem and biophys acta 1959;32:586-7.
13. Ehringer H, Hornykiewicz O. Distribution of Noradrenalin and Dopamin
(3-Hydroxytryramin) in the human brain and their behaviour in diseases of the
extrapyramidal system. Klin Wochenschr 1960;38:1236-9.
14. Hornykiewicz O. Levodopa in the 1960s: starting point Vienna, in 20 years of
Madopar – New avenues. A.J. Lees AJ, editor. Basel: Editiones Roche; 1994. p. 11-7.
15. Pletscher A. Die Geburt von Madopar: Ratio und Fortuna, in L-dopa Substitution der
Parkinson-Krankheit. Umek PRaH, editor. New York: Springer-Verlag; 1985. p. 3-12.
16. Hornykiewicz O, Birkmayer W. Biochemisch – pharmakologische Grundlagen für die
Anwendung von L-Dioxyphenylalanin beim Parkinsonsyndrom. Wien Med
Wochenschr 1961;73:839-40.
17. Birkmayer, W, Hornykiewicz O. Der L-3,4-Dioxyphenylalanin (= Dopa)-Effekt bei der
Parkinson-Akinese. Wien Klin Wochenschr 1961;73:787-8.
18. Barbeau A, Murphy G, Sourkes T. Excretion of dopamine in diseases of basal ganglia.
Science 1961;133:1706-7.
19. Barbeau A. Biochemistry of Parkinson’s disease. In: Proceedings of the 7th
International congress of Neurology. Rome: Societa Grafica Romana; 1961. p. 925.
20. Barbeau A, Sourkes TL, Murphy GF. Les catecholamines dans la maladie de
Parkinson. In: De Ajuriaguerra J, editor. Monoamines et système nerveux central.
Paris: Masson; 1962. p. 247-62.
21. Reimann R. Der Forschungsbericht über die Entwicklung der Behandlung des Morbus
Parkinson (1817-1970). In: Kapp W, Leickert KH, editors. Basle: Hoffmann-La Roche
AG; 1971. p. 23-35.
22. Cotzias G, Papavasiliou P. Therapeutic studies of Parkinsonian patients: long-term
effects of D-L and L-dopa. In: Barbeau A, Brunette J-R, editors. Amsterdam: Excerpta
Medica; 1967. p. 357-65.
23. Cotzias G, Papavasiliou P, Gellene R. Modofication of parkinsonism: Chronic
treatment with L-dopa. N Engl J Med 1969;280:337-45.
24. Burkard WP, Gey FK, Pletscher A. A new inhibitor of decarboxylase of aromatic
amino-acids. Experientia 1962;18:411.
25. Bartholini G, Burkard WP, Pletscher A. Increase of cerebral catcholamines caused by
3,4-dihydroxyphenylalanine after inhibition of peripheral decarboxylase. Nature
1967;215:852-3.
26. Birkmayer W, Mentasti M. Weitere experimentelle Untersuchungen über den
Catcholaminstoffwechsel bei extrapyramidalen Erkrankungen. Arch Psychiat
Nervenkr 1967;210:29-35.
27. Birkmayer W. Experimentelle Ergebnisse über die Kombinationsbehandlung des
Parkinsonsyndroms mit L-dopa und einem Decarboxylasehemmer (Ro 4-4602).
Wien Med Wochenschr 1969;81:677-9.
28. Siegfried J, Klaiber R, Perret E, et al. Treatment of Parkinson’s disease with L-dopa
combined with a decarboxylase inhibitor. Pharmacol Clin 1969;94:2678-81.
29. Jaffe GM, Rehl WR. Process for the preparation of L-dopa in the United States patent
3714242. Hoffmann-La-Roche Inc., USA. 7 June 1970.
30. Kaiser A. Process for the preparation of L-dopa in the United States patent 3969397.
Hoffmann-La-Roche Inc., USA. 27 December 1968.
31. Birkmayer W, Linauer W, Mentasti M. Traitement à la L-DOPA combinée avec un
inhibiteur de la décarboxylas (Ro-4–4602). In: Gauthier JDAAG, editor. Monoamines
noyaux gris centraux et syndrome de Parkinson. Geneva: Georg & Cie; Paris: Masson
& Cie; 1971.
32. Siegfried J. La L-dopa associée an un inhibiteur de la décarboxylase dans le traitment
actuel de la maladie de Parkinson. In: Gauthier G, editor. Monoamines noyaux gris
centraux et syndrome de Parkinson. Geneva: Georg & Cie; Paris: Masson & Cie;
1971.
33. Tissot R, Gauthier J. Thérapeutique du syndrome parkinsonien par la L-dopa associée
a des inhibiteurs de la décarboxylase.In: Gauthier G, editor. Monoamines noyaux gris
centraux et syndrome de Parkinson. Genève: Georg & Cie; Paris: Masson & Cie;
1971.
34. Theiss E, Schärer K. Toxicity of L-dopa and a decarboxylase inhibitor in animal
experiments. In: Gauthier G, editor. Monoamines noyaux gris centraux et syndrome
de Parkinson. 1971. Genève: Georg & Cie; Paris: Masson & Cie; 1971.
35. Ziegler WH, Falcato J, Kapp W. Toxicity of L-dopa and a decarboxylase inhibitor in
humans. In: Gauthier G, editor. Monoamines noyaux gris centraux et syndrome de
Parkinson. Genève: Georg & Cie; Paris: Masson & Cie; 1971.
36. Schärer K. Experimental data on rat epiphyseal cartilages and their significance for
growing and adult humans. Verh Dtsch Ges Pathol 1974;58:294-7.
37. Knowles WS. Asymmetric hydrogenations, Nobel lecture.
http://www.nobel.se/chemistry/laureates/2001/knowles-lecture.pdf, 2001.

June 23, 2014 Posted by Chris | History, Parkinsons Disease | Leave a Comment