PARKINSON’S DISEASE

Pharmacotherapeutics III

By

Sohel Memon

(Doctor of Pharmacy)

TOPICS TO BE DISCUSSED

1. Definition

2. Epidemiology

3. Etiology

4. Risk factor

5. Types

6. Signs and Symptoms

7. Pathophysiology

8. Staging

9. Complications

10. Diagnosis

11. Pharmacotherapy

DEFINITION

Parkinson’s disease (PD) is a slow, progressive, neurodegenerative disease of the extrapyramidal motor system.

Dopamineneurons in the substantia nigra are primarily affected, and degeneration of these neurons causes a disruption in the ability to generate body movements.

EPIDEMIOLOGY

PD already the second most common neurodegenerative disease of mid-to-late life in developed countries, will become increasingly prevalent in developed countries in this century.

In India PD has a low prevalence except in the small Parsi community.

In United States (US) and Western Europe.

An estimate of approximately 10million people worldwide are living with Parkinson’s Disease.

Age Incidence

60 – 69year ~1 in 200

70’s ~1 in 100

80’s ~1 in 35

PREVALENCE OF PARKINSON’S DISEASE

ETIOLOGY

1. Age – more than 60years.

2. Positive family history and Race.

3. Environmental Exposure: Herbicide and pesticide exposure, metals( manganese,iron) and steel alloy industries.

4. Exposure to MPTP (1- methyl-4-phenyl-1,2,3,6 tetrahydropyridine), a potent neurotoxin.

5. Environmental factors such as rural living,drinking well water.

6. Life experiences (trauma,emotional stress).

7. An INVERSE correlation between cigarette smoking and caffeine intake in case-control studies.

RISK FACTOR

Age. Young adults rarely experience Parkinson's disease. It ordinarily begins in middle or late life, and the risk increases with age. People usually develop the disease around age 60 or older.

Heredity. Having a close relative with Parkinson's disease increases the chances that you'll develop the disease. However, your risks are still small unless you have many relatives in your family with Parkinson's disease.

Sex. Men are more likely to develop Parkinson's disease than are women.

Exposure to toxins. Ongoing exposure to herbicides and pesticides may put you at a slightly increased risk of Parkinson's disease.

TYPES

1. Primary or Idiopathic Parkinsonism The cause of the disease is unknown. Predominantly affecting the individuals over 60years of

age. Over the years the dopaminergic neurons degenrate

due to

H2O2 and free radicals such as O2-(superoxide) and OONO-

(Peroxynrite).

2. Secondary or Drug Induced Parkinsonism• There is no degeneration as seen in above case, but

the

decrease ion dopamine is drug induced.

SIGNS AND SYMPTOMS

SIGNS AND SYMPTOMS (SSS)

1. Increased muscular stimuation leading to involuntary tremors which occurs when the person sits or even at rest(resting tremors).

2. Typical pill rolling movement of fingers and nodding of head

3. Bradykinesia- Difficulty and slowness of movements.

4. Rigidity of muscles leading to masked appearance of face.

5. Jerk during voluntary movements.

6. Aphonia- loss of volunatry control of muscles of mouth and larynx leadint to loss of speech.

7. Posture and Gait:

- Gait is characterized by short steps,with feet barely leaving the groung,producing an audible shuffling noise.

- Stooping posture- forward flexed posture

- Dystonia- Abnormal, sustained, painful twisting muscle contractions,often affecting the foot and ankle.

8. Excessive secretion of salivary glands i.e sialorrhoea and sebaceous glands

i.e seborrhoea

9. Absence of control over movements of eye.

10. Memory Disorder, loss of personal interest, loss of reasoning and orientation.

PATHOPHYSIOLOGY

The dopaminergic neuron from substantia nigra pars compacta act on excitatory D1 receptors in the striatum and causes excitation of the striatal neurons in the direct pathway.

The excitation is neutralized when the dopaminergic neurons from the substantia nigra pars compacta act on inhibitory D2 receptors in the stratum and cause the inhibition of the striatal neurons in the indirect pathway.

In direct pathway, the globus pallidus medial is innervated via ihibitory GABAergic neurons from the striatum.

Similarly, the neurotransmission from this region to the thalamus is also carried out by inhibitory GABAergic neurons.

However,the nervous innervation from the thalamus to the cortex is via the excitatory glutaminergic neurons which results in voluntary movements

In the indirect pathway,similar to the direct pathway,the nervous innervation from the striatum to globus pallidum lateral from these regions to subthalmic nucleus is through inhibitory GABAergic neurons.But the transmission from the subthalmic nucleus to globus pallidus medial is through excitatory glutaminergic neurons.

The basic difference between two pathways is the type of innervation to the two mentioned regions(globus pallidus medials and substantia nigra par reticulus).

In direct pathway the innervation is inhibitory while in indirect pathway it is excitatory in nature.

Hence any alterations in the innervation to the globus pallidus medial and substantia nigra par reticulata ultimately affect the neurotransmission to the cortex, which results in either enhancement or suppression of voluntary movements.

Physiologically,dopamine causes the activation of direct pathway and inhibition of indirect pathway.

This results in excitation of cortex,leading to voluntary movements.

In parkinsonism,where the dopamine gets depleted due to destrution of dopaminergic neurons,the direct pathway get suppressed while the indirect pathway get overstimulated.This leads to decreased excitatory outflow to the motor cortex resulting in the suppression of voluntary movements

Clinical features don’t emerge until >60-80% dopamine lost.

Compensatory changes include hyperactivity in remaining neurones (increased transmitter turnover), increase in dopamine receptors; receptor supersensitivity.

Other pigmented nuclei also affected (locus ceruleus and raphe). Also cortex and other structures affected.

Characteristic histological inclusion in affected neurons are eosinophilic cytoplasmic inclusions in nigral cells called the Lewy Bodies.

Basal Ganglia Controls movement

Dopamine Inhibitory

neurotransmitter in the basal ganglia

Acetylcholine Excitatory

neurotransmitter in the basal ganglia

Without dopamine, inhibitory influences are lost and excitatory mechanisms are unopposed

Neurons of basal ganglia are over stimulated

Excess muscle tone, tremors & rigidity

Extrapyramidal system next lecture!

HOEHN AND YAHR STAGING OF PARKINSON'S DISEASE

1. Stage 1: Mild signs and symptoms on one side only, not disabling but friends notice.

2. Stage 2: Symptoms are bilateral, minimal disability, posture and gait affected

3. Stage 3: Significant slowing, dysfunction that is moderately severe

4. Stage 4: Severe symptoms, walking limited, rigidity, bradykinesia, unable to live alone

5. Stage 5: Cachectic, complete invalidism, unable to stand, walk, require nursing care

COMPLICATIONS Thinking difficulties. Depression and emotional changes.. Swallowing problems. . Sleep problems and sleep disorders.  Bladder problems Constipation

You may also experience: Blood pressure changes.  Smell dysfunction.  Fatigue Pain. Sexual dysfunction

DIAGNOSIS

1. Neurological History

2. Response to levodopa

3. Imaging and Laboratory examination

4. Physical Examination

There are no standard diagnostic tests for Parkinson’s.

1. Neurological History The doctor looks to see if your expression is animated. Your arms are observed for tremor, which is present either when

they are at rest, or extended. Is there stiffness in your limbs or neck? Can you rise from a chair easily? Do you walk normally or with short steps, and do your arms swing

symmetrically? The doctor will pull you backwards. How quickly are you able to regain your balance?

2. Response to levodopa A person’s good response to levodopa (which temporarily

restores dopamine action in the brain) may support the diagnosis.  

DIAGNOSIS

The main role of any additional testing is to exclude other diseases that imitate Parkinson’s disease, such as stroke or hydrocephalus.

3. Imaging and Laboratory examination

a. Blood test - usually to rule out any other condition, such as abnormal thyroid hormone levels or liver damage.

b. MRI or CT scan - to check for signs of a stroke or brain tumor. If there is/was no stroke or brain tumor, most MRI or CT scans of people with Parkinson’s disease will appear normal.

c. PET (positron emission tomography) scan –

this imaging test may sometimes detect low

levels of dopamine in the brain.

4. Physical Examination: Two of the four main symptoms must be present - for a

neurologist to consider a Parkinson’s disease diagnosis, the patient must have two of the four main symptoms.

They must be present over a specific period. The four main symptoms are:

Tremor or shaking Bradykinesia - slowness of movement Rigidity (stiffness) of the arms, legs or trunk Postural instability - balance problems and possible falls

MANAGEMENT

1. Pharmacotherapy2. Non-Pharmacotherapy3. Surgery

ANTI-PARKINSONS DRUG

1.Dopaminergic drugsa. Dopamine precursor

b. Peripheral Decarboxylase Inhibitors

c. Dopamine agonist i). Ergot derivatives

ii). Non- ergot derivatives

d. MAO-B Inhibitors

e. Dopamine facilitator

f. COMT iInhibitors

2.Anticholinergic Drugsa. Anti-cholinergics

b. Anti-histamines

1. Dopaminergic drugsa. Dopamine preacursor - Levodopa

b. Peripheral Decarboxylase Inhibitors - Carbidopa

- Benserazide

c. Dopamine agonist i). Ergot derivatives

- Bromocriptine

- Pergolide

- Lisuride

- Carbergolin

ii). Non- ergot derivatives

- Piribedil

- Ropinirole

- Pramipexole Apomorphine

- Rotigotine

d. MAO-B Inhibitors

- Seleginine

- Rasagiline

e. Dopamine facilitator - Amantadine

f. COMT Inhibitors

- Entacapone

- Tolcapone

2.Anticholinergic Drugsa. Anti-cholinergics

- Trihexyphenidyl

- Benztropine

- Procyclidine

- Biperiden

b. Anti-histamines - Diphenhydramine- - Orphenadrine- - Promethazine

LEVODOPA

Well absorbed from gut, but > 90% is decarboxylated to dopamine peripherally in GIT& blood vessels & only a small proportion reaches the brain (dopamine does not readily cross BBB). Therefore combined with peripheral decarboxylase inhibitor that does not cross the blood-brain barrier along with L-DOPA.

Peripheral decarboxylase inhibitors, carbidopa & benserazide, are available as combination preparations with levodopa, as Sinemet & Madopar, respectively.

CARBIDOPA

Is a structural analogue of L-dopa.

Inhibits the conversion of L-dopa to dopamine in peripheral tissue

Carbidopa is highly ionized at physiological pH and does not cross the blood-brain barrier, so it does not inhibit the formation of dopamine in CNS

It reduces GI and cardiovascular side effects of L-dopa and enables about 75% reduction in dosage of L-dopa

L-dopa-carbidopa sustained release combination designed to reduce “wearing off” effect

Drug Dose MOA Diagram

Dopaminergic drugsa. Dopamine

preacursor - Levodopa

 I: 125 mg BD M: 8 g/day

Levodopa increases dopamine levels in the brain leading to the stimulation of dopamine receptors.

b. Peripheral Decarboxylase Inhibitors

- Carbidopa

Initial: 25mg tab TDMax: 8 tab/day

Inhibits the conversion of L-dopa to dopamine in peripheral tissue

c. Dopamine agonist -Bromocriptine

1 mg initially, -sed to 2.5 mg ,TD up to 30 mg/day.

Bromocriptine is a dopamine D2 and D3-agonist which works by activating postsynaptic dopamine receptors

Drug Dose MOA Diagram

MAO-B Inhibitors

- Seleginine

10 mg/day in single or divided doses

Selegiline increases dopaminergic activity by intervening with the re-uptake of dopamine at the synapse. It also irreversibly inhibits the MAO-B which is involved in the metabolism of dopamine.

Dopamine facilitator

- Amantadine

100 mg/day, up to 100 mg twice daily Max: 400 mg/day.

Amantadine is a weak dopamine agonist possessing antimuscarinic properties. It alters dopamine release and re-uptake. It also noncompetitively antagonises N-methyl-D-aspartate.

Drug Dose MOA Diagram

COMT Inhibitors

- Entacapone

PO 200 mg w/ each levodopa/dopa decarboxylase inhibitor dose. Max: 200 mg

Entacapone is a selective, reversible, peripheral inhibitor of COMT, an enzyme involved in the metabolism of dopamine and levodopa.

Anticholinergics - Bromocryptine

Initial: 1 mg/day in divided doses, gradually up to 6-10 mg/day

Trihexyphenidyl is a tertiary amine antimuscarinic, which competitively inhibits the effects of acetylcholine at the muscarinic receptors of autonomic effector sites

Anticholinergics

Benztropine (Cogentin), trihexyphenidyl (Artane)

Dry mouth, dry eyes, constipation, hypotension, cognitive impairment, urinary retention

Useful for symptomatic control of Parkinson’s disease (benefits are mild to moderate); associated with more adverse effects than other drugs

Carbidopa/levodopa

Immediate- and sustained-release carbidopa/levodopa (Sinemet)

Nausea, somnolence, dyskinesia, hypotension, hallucinations

Levodopa is the most effective medication and remains the primary treatment for symptomatic Parkinson’s disease; no added benefit for motor complications with sustained-release versus immediate-release preparations

ADRs Indications

COMT inhibitors

Entacapone (Comtan)

Diarrhea; exacerbates levodopa adverse effects; bright orange urine

Useful for managing motor fluctuations (“wearing-off” effect) in patients taking levodopa; levodopa dose may need to be reduced if dyskinesia appears

Tolcapone (Tasmar)

Diarrhea; exacerbates levodopa adverse effects; rare liver failure (liver function monitoring needed)

Dopamine agonists

Bromocriptine (Parlodel)

Nausea, headache, dizziness

Useful for early and advanced disease

Pergolide (Permax)

Somnolence; hallucinations; nausea; edema; fibrosis of cardiac valves, lung, and retroperitoneum; retroperitoneal and pulmonary fibrosis

Useful for the initial treatment of parkinsonism and as adjunct therapy in patients taking levodopa

MAO-B inhibitors

Selegiline (Eldepryl) Nausea, insomnia, drug interactions with other MAO inhibitors/tyramine

Useful for symptomatic control of Parkinson’s disease (benefits are mild to moderate) and as adjuvant therapy for patients with Parkinson’s disease and motor fluctuationsRasagaline (Azilect) Weight loss,

hypotension, dry mouth, drug interactions with other MAO inhibitors/tyramine

NMDA receptor inhibitor

Amantadine (Symmetrel)

Nausea, hypotension, hallucinations, confusion, edema

Useful for treating akinesia, rigidity, tremor, dyskinesia

SURGERY

1. Deep brain stimulation

2. Pallidotomy

3. Thalamotomy

Deep brain stimulation  Affects movement by using electrical impulses to

stimulate a target area in the brain. The electrical impulses are generated by wire electrodes surgically placed in the brain. Deep brain stimulation may be used in addition to therapy with levodopa or other drugs when drugs alone do not control symptoms adequately.

It does not destroy brain tissue and has fewer risks than older, more destructive surgical methods, such as pallidotomy and thalamotomy.

Pallidotomy involves the precise destruction of a very small area in the deep part of the brain (the globus pallidus) that causes symptoms.

Thalamotomy involves the precise destruction of very small area in the deep part of the brain (the thalamus) that causes symptoms.

NON- PHARMACOLOGICAL TREATMENT

Healthy eating Eat a nutritionally balanced diet that contains plenty of fruits,

vegetables and whole grains. Eating foods high in fiber and drinking an adequate amount of fluids can help prevent constipation that is common in Parkinson's disease.

A balanced diet also provides nutrients, such as omega-3 fatty acids, that may be beneficial for people with Parkinson's disease.

Exercise Exercising may increase your muscle strength, flexibility and balance.

Exercise can also improve your well-being and reduce depression or anxiety.

Try not to move too quickly. Aim for your heel to strike the floor first when you're walking. If you notice yourself shuffling, stop and check your posture. It's best to stand up straight. Look in front of you, not directly down, while walking.

.

Avoiding falls In the later stages of the disease, you may fall more easily. The following suggestions may help: Make a U-turn instead of pivoting your body over your feet. Keep your center of gravity over your feet without leaning

or reaching. Avoid carrying things while you walk. Avoid walking backward.

Daily living activities Daily living activities — such as dressing, eating, bathing

and writing — can be difficult for people with Parkinson's disease. An occupational therapist can show you techniques that make daily life easier

THANK YOU!!!