How PD medications work There are a number of medications available to help treat Parkinson’s disease. You’ll find your doctor may use several different medications to treat your symptoms. He or she will usually start with one, then add or change others as your symptoms change. The reason we can use these different medications together is because they each have different strategies for managing the decline of dopamine in the brain. Today, we’ll talk about 4 basic categories and how they work in the brain. What you are looking at is 2 neurons, or dopamine-producing cells in the brain, and the “D’s” represent dopamine. The types of medications we’ll talk about today are levodopa, COMT inhibitors, dopamine agonists, and MAO-B inhibitors.
In Western medical literature it was described by the
physician Galen as "shaking palsy" in 175 AD.
In 1817 a detailed medical essay was published on the
subject by London doctor James Parkinson.
Jean-Martin Charcot was the first to truly recognise the
importance of Dr.Parkinson's work and renamed the
disease which was formerly named paralysis
agitans (shaking palsy) after him.
Begins between 40 and 70 years of age.
Peak age of onset at sixth decade.
Infrequent before 30 years of age.
More common in men.
Trauma, emotional upset, overwork, exposure to
cold, rigid personality etc. are suggested to be
the predisposing factors to the disease but none
Disease observed in all countries and all races.
Parkinsonism and Parkinson’s
Parkinsonism is a clinical syndrome characterised
primarily by bradykinesia, with associated
increased tone (rigidity), tremor and loss of
postural reflexes. There are many causes but the
most common is Parkinson’s disease (PD).
When parkinsonism features are present in a
person without any established etiology it is called
Genetic abnormalities resulting in protein misfolding and
accumulation and mitochondrial dysfunction ,are found to
be responsible for causing PD.
Protein accumulation can be due to increased formation or
Mutation in the Park1 gene encoding the protein alpha-
synuclein, a main component of lewy body, on the
chromosome 4q are seen in early onset (mean age 46 years)
Mutations in parkin (a ubiquitin ligase that attaches ubiquitin
to misfolded proteins to promote their transport to the
proteasome for degradation) and UCH-L1 (which cleaves
ubiquitin from misfolded proteins to permit their entry into the
proteasome) are causative in other cases of familial PD.
Mitochondrial dysfunction has also been implicated in familial
PD. Genes involved (parkin, PINK1, and DJ1).
Having first degree relative with PD confers a 2-3 times
increased risk of developing Parkinson’s disease.
What is Parkinson’s
“Involuntary tremulous motion, with
lessened muscular power, in parts not
in action and even when supported,
with a propensity to bend the trunk
forward, and to pass from a walking
to running pace : the senses and the
intellects being uninjured”
The presence of two out of the three cardinal features of
bradykinesia, rigidity and tremor; postural instability tends
to occur later.
A good clinical response to levodopa; and
No ‘atypical’ features suggestive of another parkinsonian
There is extensive loss of pigmented
dopaminergic substantia nigra neurones and the
presence of lewy bodies.
CONNECTIONS OF BASAL GANGLIA
BASAL GANGLIA IN PARKINSON’S
LEAD PIPE -TRUNK &LOWER LIMB
TRUNK -STOOPED AND FLEXED
COG WHEEL –UPPER LIMB
GAIT/POSTURAL REFLEXES DISTURBED
DIFFICULTY IN MAINTAINING BALANCE
SLOW TO START WALKING
RAPID SMALL STEPS (TENDENCY TO RUN)
REDUCED ARM SWING
DIFFICULTY IN STOPPING SUDDENLY
IMPAIRED BALANCE ON TURNING
HYPOKINESIA & BRADYKINESIA
SLOWNESS IN INITIATING AND
REPEATING VOLUNTARY MOVEMENTS
DESPITE NORMAL STRENGTH
RESTING – 4 TO 6 Hz
↓ WITH MOVEMENT AND ATTENTION
POSTURAL -8 TO 10 Hz
PERSIST ON MOVEMENT
Often Involves the hand.
Pill-rolling tremors (four per second) involving
thumb and fingers are characteristic.
Typically present when the hand is at rest ( hence
the term RESTING TREMOR).
Voluntary movements dampens the tremors
Complete relaxation ( sleeping) greatly reduces
or abolishes the tremor .
Also known as alternating tremors due to
alternating burst of activity in agonist and
antagonist muscles in EMG.
Second common type is
A fine, seven to eight per second tremors of the
outstretched hands and fingers.
Persists throughout voluntary movements.
Not evident in resting position.
More easily suppressed by relaxation.
Lacks the alternating burst of action potential
unlike resting tremors and resembles essential
Parkinson’s disease patients may have either type
of tremor or both.
Muscles are continuously or
intermittently firm and tense.
Present when patient is in
awakened state, even when
appearing quiet and relaxed.
Unlike spasticity it lacks the initial
“free interval” on passive flexion
thus having the quality of
bending a lead pipe.
Limb does not resume its original
position as happens in spasticity.
Rigidity involves both flexor and extensor muscles but
predominant in flexors.
Small muscles of face, tongue, larynx are also affected.
Cogwheel phenomenon: Rigidity with superimposed
tremor. Passive flexion of hypertonic muscles causes
rhythmically interrupted ratchet like resistance.
Once rigidity develops it is constantly present.
Initially unilateral later becomes bilateral.
Tendon reflexes are not enhanced.
Babinski is negative.
HYPOKINESIA AND BRADYKINESIA
Hypokinesia is defined as
“Disinclination on the part of the patient to use an
affected part and to engage it freely in all the natural
actions of the body”.
The frequent automatic habitual movements are
absent or reduced.
Blinking is infrequent & Face lacks expressive mobility.
Reduced arm swing while walking.
On looking to one side eyes moves but not the head.
There is a lack of the small “movements of
cooperation” (as in arising from the chair without first
adjusting the feet).
Handwriting becomes small (MICROGRAPHIA)
blinking ,5-10 per
Soft voice and
hypomimia) Drooling of saliva
Bradykinesia refers to reduced velocity of the
movement, or the time from onset to completion of
movement is slower than normal.
Reaction time ( time interval between the command
and the first contraction of the muscle) is also
Saliva is not swallowed as quickly as it is produced.
Inability to carry out quick (ballistic) movements.
Inability to inhibit blinking in response to a tap over the
bridge of the nose or glabella (Myerson sign).
Involuntary flexion of the trunk limbs and
Hesitation in starting to walk.
Steps are short and the feet barely clears
the ground as patient shuffles along.
Once walking started patient takes
increasingly short and rapid steps as
though trying to catch up to his centre of
Freezing briefly when encountering
doorways or other obstacles.
Diminished or reduced arm swing.
Turning en bloc.
Inability to make appropriate postural adjustments to
tilting and falling.
Anticipatory and compensatory righting reflexes are
Initially the only complaints
may be of aching of the back,
neck, shoulders, or hips and of
Persistent extension or clawing
of the toes, jaw clenching, and
other fragments of dystonia,
often painful, may be present
but are not usually early
findings. (These are particularly
resistant to treatment.)
Depression, anxiety, dementia, hallucinations.
Impaired memory is usually not a major feature of
Dementia correlates with increase in number of lewy
Hypotension (levodopa, dopa agonists)
Modified Hoehn And Yahr Staging
Stage 0 – No signs of disease.
Stage 1 – Unilateral disease.
Stage 1.5 – Unilateral plus axial involvement.
Stage 2 – Bilateral disease, without impairment of balance.
Stage 2.5 – Mild bilateral disease with recovery on pull test.
Stage 3 – Mild to moderate bilateral disease; some postural
instability; physically independent.
Stage 4 – Severe disability; still able to walk or stand
Stage 5 – Wheelchair bound or bedridden unless aided.
UK Parkinson's disease society brain
bank clinical diagnostic criteria
Only useful for research purpose.
Diagnosis is only based on clinical features.
Imaging can be useful in difficult cases or research studies.
Genetic testing may be useful in identifying at-risk individuals
in research setting.
The most effective symptomatic treatment for PD and the
gold standard against other drugs.
Combination reduces oral doses and reduce Acute
dopaminergic side effects like nausea, vomiting, and
Combinations of carbidopa-levodopa are available in a l:10
or 1:4 ratio and the benserizide-levodopa combination in a
The initial dose of levodopa-carbidopa is typically one-half
to one of a 25/100-mg tablet given two or three times daily
and increased slowly until optimum improvement is
Dietry protein interferes with absorption of levodopa.
Taking medications 1 hour before food or 2 hours after
food can lead to more predictable and effective
absorption and improved stability.
Controlled release levodopa reduces the number of
doses but associated with slow onset of action
particularly in morning. Addition of conventional dose at
this time can provide a initial ‘kick in’.
Mild off periods respond well to small supplemental
doses in fast acting form like dispersible tablets which
acts rapidly but short acting.
Side effects of levodopa
Anorexia, nausea, and vomiting-stimulation of ctz.
Tachycardia, ventricular extra systoles and
Psychotic patients-exacerbation of symptoms.
Vitamin B6 [pyridoxine] increases peripheral
degradation of levodopa
Motor complications of
These are limitation of the long-term use of levodopa therapy
"wearing off" phenomenon:
Each dose of levodopa effectively improves mobility for a
period of time, perhaps 1-2 hours, but rigidity and akinesia
return rapidly at the end of the dosing interval.
They occur at later stage of the disease.
Increasing the dose and frequency of administration can
improve this situation, but this often is limited by the
development of dyskinesias.
In more advanced states, patients may cycle between "on"
periods complicated by disabling dyskinesias and "off"
periods in which they suffer severe parkinsonism.
This may occur in a matter of minutes or from one hour to the
Peak-dose dyskinesia :
Many patients develop dyskinesias at the time of maximal
clinical benefit and peak plasma concentration.
They are usually choreiform in nature but can manifest as
dystonia, myoclonus, or other movement disorders.
Occur as the levodopa dose begins to take effect and again
as it wears off.
Changes in motor response associated
with chronic levodopa treatment
Reduces "off" time and prolongs "on" time and more beneficial
in patients treated with levodopa+carbidopa combination
having motor fluctuations.
Tolcapone and entacapone are approved drugs.
Side effects are dopaminergic(nausea ,vomiting ,increased
Diarrhoea = tolcapone > entacapone.
Fulminant Hepatic necrosis reported with tolcapone so LFT
monitoring is important.
It is not reported with entacapone.
Discolouration of urine is reported.
Block central dopamine metabolism and increase synaptic
concentrations of the neurotransmitter.
Reduce "off" time when used as an adjunct to levodopa in
patients with motor fluctuations.
Well tolerated and reduces the required dose of levodopa.
Early reports of possible neuroprotective effects of selegiline
have not been supported by long-term studies.
Selegiline is metabolized to methamphetamine and
amphetamine, whose stimulating properties may produce
insomnia. But not rasageline.
High dose of these drugs can cause hypertensive crisis known as
Originally introduced as an antiviral agent.
It is the only anti parkinsonian drug that improves levodopa
According to recent studies it acts by inhibiting NMDA receptors,
increases presynaptic dopamine reuptake and release.
less efficacious than levodopa.
Has little effect on tremor, but it is more effective than the
anticholinergics against rigidity and bradykinesia.
Adverse effects are livido reticularis, ankle edema, urinary
dysfunction, glaucoma, and particularly cognitive impairment.
Longer duration of action than levodopa thereby
causing lesser risk of developing dyskinesias.
Ergot derivatives are not used now due major cardiac
In early PD it delays the need to start levodopa therapy.
In late PD it helps to reduce the dose of levodopa.
Apomorphine is available only as I.V preparation.
Rotigotine is available as transdermal patches.
Adverse effects like hypersexuality and pathological
gambling also seen.
Younger patients less than 60 yrs who are at more risk of
developing dyskinesia are more likely to tolerate agonists.
Agonist monotherapy is associated with fewer motor
Agonist monotherapy is unlikely to be adequate for more
than 5 years.
Aim of agonist monotherapy is to delay the levodopa
therapy and not to avoid it altogether.
Used in early stages when symptoms are not
Useful against tremors but not against other
symptoms of PD.
Side effects are dry mouth, blurring of vision,
glaucoma, hallucinations and prostatic
Use is limited in elderly due to the side effects.
Steriotactic lesions placed in motor cortex improved tremors
but produced motor deficits.
lesions placed into the VIM nucleus of the thalamus reduced
contralateral tremor without inducing hemiparesis.but not
improved other symptoms.
Lesions placed in the GPi improved rigidity and bradykinesia as
well as tremor.
Pallidotomy was also associated with marked improvement in
These procedures were not optimal for patients withbilateral
Deep brain stimulation
An electrode is placed into the target area and
connected to a stimulator.
DBS simulates the effects of a lesion without
necessitating a brain lesion.
It does not require making a lesion in the brain and is
thus suitable for performing bilateral procedures with
DBS for PD primarily targets the STN or the GPi. It
provides dramatic results, particularly with respect to
"off" time and dyskinesias.
Management of non-motor
Depression- SSRI’s. Antidepressants should not be withheld, particularly
for patients with major depression.
Anxiety-Short acting benzodiazepines.
Psychosis-low dose neuroleptics: Clozapine is most effective (A.E:
Agranulocytosis). Quetiapine is also used.
Dementia-Levodopa and other dopaminergic drugs can aggravate
cognitive function in demented patients and should be stopped or
Anticholinesterase agents such as rivastigmine and donepezil reduce
the rate of deterioration. Memantine, an antiglutamatergic agent,
may also provide benefit for some PDD patients.
Orthostatic hypotension- Adding salt to the diet and
elevating the head of the bed. Low doses of fludrocortisol
(Florinef) or midodrine control most cases.
Sexual dysfunction can be helped with sildenafil or tadalafil.
Urinary problems- cholinergics are helpful.
Sleep disturbances- low dose clonazepam.
Other aspects of
Physiotherapy , Occupational therapy, Speech
therapy are helpful in advanced cases with
Intensive social support in the community is
Residential care may be the only option in some
Recent advances in
Levodopa-carbidopa Gel [duodopa]:
continuously deliverd through duodenostomy or
jejunostomy tube into intestine. More invasive.
Constant levels are maintained.
PARDOPRUNOX, has progressed to Phase III trial.
APLINDORE, is being studied in a Phase II trial.
LISURIDE, which is in the form of a skin patch and is
already marketed in Europe, has progressed to a
Phase II trial.
NEBICAPONE, has shown promising results in preliminary
SAFINAMIDE, is being studied in a Phase III trial.
Non dopaminergic agents:
Adenosine A2A antagonist: ISTRADEFYLLINE, was taken
to Phase III trials, but it failed to prove effective.
FIPAMEZOLE (JP-1730), SCH-420814, BIIA-014 and Lu
AA4707 — are in earlier phases of development.
FP0011, a compound that reduces central glutamate
levels, is now being studied in a Phase II trial.
A metabotropic glutamate (mGlu5) receptor
antagonist has completed a Phase I trial.
Cell-based therapies (such as transplantation of fetal
nigral dopamine cells or dopamine neurons derived
from stem cells), gene therapies, and trophic factors
are under experimentation.
Multiple System Atrophy [MSA]
Characterised by parkinsonism, autonomic failure and
cerebellar symptoms, with either parkinsonism (MSA-P) or
cerebellar features (MSA-C) predominating.
Early falls, postural instability and lack of response to LD are
clues for diagnosis.
The pathological hallmark is α-synuclein containing glial
cytoplasmic inclusions found in the basal ganglia, cerebellum
and motor cortex.
Management is symptomatic and the prognosis is less good
than for PD, with mean survival from symptom onset of fewer
than 10 years, and early disability.
Cognition is preserved.
Progressive supranuclear palsy (PSP)
Presents with symmetrical parkinsonism, cognitive
impairment, early falls and bulbar symptoms.
The characteristic eye movement disorder, with slowed
vertical saccades leading to impairment of up and down
gaze, may take years to emerge.
Pathology: Abnormal accumulation of tau (τ) proteins and
degeneration of the substantia nigra, subthalamic nucleus
There is no treatment, and the parkinsonism usually does
not respond to LD.
less common than MSA or PSP.
Clinical manifestations are variable, including parkinsonism,
dystonia, myoclonus and ‘alien limb’ phenomenon,
whereby a limb (usually upper) moves about or interferes
with the other limb without apparent conscious control.
Cortical symptoms, especially apraxia, are common and
may be the only features in some cases, including
CBD is a tauopathy with widespread deposition throughout
the brain, and has similar survival rates to MSA and PSP.
SYMPTOMS/SIGNS ALTERNATIVE DIAGNOSIS TO
Falls as first symptom PSP
Exposure to neuroleptics Drug-induced parkinsonism
Onset prior to age 40 If PD think of genetic cause
Early Hallucinations Lewy body dementia
Sudden onset of
Demetia as 1st symptom Lewy body dementia
Prominent orthostasis MSA-p
Early dysarthria MSA-c
Lack of tremors Various parkisonian plus
High frequency (8-10 Hz)
Parkinsonism caused by disturbance in substantia
Tremor is typically at rest with frequency 4-8 Hz.
Normal deep Tendon reflexes.
Plantar – flexor (Negative Babinski).
Masked expressionless face.
Slurred indistinct speech.