DRUGS ACTING ON NERVOUS SYSTEM
PREPARED BY MR. ABHIJIT DAS
ANALGESICS:
NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)
ANALGESIC:
An analgesic is a drug that relieves pain.
NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS)
NSAIDs are medications that reduce pain,
inflammation, and fever by blocking certain enzymes in the body.
CLASSIFICATION OF NSAIDS:
A. Nonselective
COX inhibitors
1. Salicylates:
Aspirin.
2. Propionic
acid derivatives: Ibuprofen, Naproxen, Ketoprofen, Flurbiprofen.
3. Anthranilic
acid derivative: Mephenamic acid.
4. Aryl-acetic
acid derivatives: Diclofenac, Aceclofenac.
5. Oxicam
derivatives: Piroxicam, Tenoxicam.
6. Pyrrolo-pyrrole
derivative: Kitorolac.
7. Indole
derivative: Indomethacin.
8. Pyrazolone
derivatives: Phenylbutazone, oxyphenbutazone.
B. Selective
COX-2 inhibitors
Celecoxib, Parecoxib, Etoricoxib.
C. Analgesic-antipyretics
with poor anti-inflammatory action
1. Paraaminophenol
derivative: Paracetamol (Acetaminophen).
2. Pyrazolone
derivatives: Metamizol (Dipyrone), Propiphenazone.
3. Benzoxazocine:
Nefopam
MECHANISM OF ACTION OF NSAIDS
The mechanism of action of NSAIDs is the inhibition of the enzyme
cyclooxygenase (COX).
In response to injury, Cyclooxygenase is required to convert arachidonic acid into thromboxanes (TXA2), Prostacyclins (PGI2), and Prostaglandins (PGE2)
Thromboxane is responsible for platelet aggregation,
prostacyclin is responsible for gastric protection and prostaglandin is responsible for pain,
fever and inflammation.
So, NSAIDs inhibit production of prostaglandins, a
group of compounds that contribute to inflammatory response and are responsible
for signs such as fever and pain.
ASPIRIN
Aspirin is acetylsalicylic acid. It is rapidly
converted in the body to salicylic acid which is responsible for most of the
actions.
MOA:
Aspirin non-selectively
inhibits COX enzyme that means aspirin inhibits both
COX-1 and COX-2. So ultimately PGE2 biosynthesis is
inhibited, which was responsible for pain, fever, and inflammation.
PHARMACOLOGICAL ACTIONS:
1. Respiration
At anti-inflammatory doses, respiration is
stimulated. Further rise in salicylate level causes respiratory depression
which may lead to death due to respiratory failure.
2. CVS
(Cardio Vascular System)
Larger doses of aspirin cause direct vasodilation so
Blood pressure may fall.
3. GIT
(Gastro Intestinal Tract)
Aspirin irritates gastric mucosa, causes nausea and
vomiting.
Aspirin also causes acute ulcer and erosive
gastritis.
4. Blood
Aspirin reduces platelet aggregation and bleeding
time is prolonged to nearly twice the normal value.
5. Immunological
effect
Aspirin inhibits antigen-antibody reaction.
ADVERSE EFFECTS:
1. At
analgesic dose aspirin causes nausea, vomiting, blood loss in stools, peptic
ulcer etc.
2. Skin
rashes of various types.
3. Bone
marrow depression leading to anaemia.
4. Hypersensitivity
reactions
5. Dizziness
THERAPEUTICAL USES:
1. As
analgesic for headache, backache, joint pain, tooth ache etc.
2. As
antipyretic against fever of any origin. Paracetamol, being safer, is generally
preferred.
3. Used
in Rheumatoid arthritis.
4. Used
in post myocardial infraction patients by inhibiting platelet aggregation.
CONTRAINDICATIONS:
1.
Allergy or hypersensitivity to aspirin
or other NSAIDs.
2.
Active peptic ulcer disease or a history
of gastrointestinal bleeding.
3.
Severe liver or kidney disease.
4.
Bleeding disorders or a tendency towards
bleeding.
DOSE AND ROUTE:
1.
For pain relief or fever reduction:
·
Adult dose: 325-650 mg every 4 to 6
hours as needed.
·
Maximum daily dose: 4 grams.
2.
For antiplatelet therapy
(prevention of heart attack or stroke):
·
Adult dose: 75-325 mg once daily.
Aspirin is commonly administered orally (ROUTE).
ROLE OF NURSE:
1.
Assessment: Nurses assess the patient's
medical history, allergies, and current medications to determine if aspirin is
appropriate for the patient's condition.
2.
Administration: Nurses administer
aspirin according to the prescribed dosage, route, and schedule, ensuring patient
safety and adherence to protocols.
3.
Monitoring: Nurses monitor patients for
adverse reactions to aspirin, such as gastrointestinal bleeding or allergic
reactions, and intervene promptly if necessary.
4.
Documentation: Nurses maintain accurate
records of aspirin administration, including dosage, route, patient response,
and any adverse events
OPIOID ANALGESICS
Opioid analgesics are drugs primarily used to relieve pain. They work by binding to opioid receptors in the brain, spinal cord, and
other areas of the body, reducing the perception of pain.
- Opium:
Opium is a natural substance derived from the sap of the opium poppy plant
(Papaver somniferum). It contains various alkaloids, including morphine
and codeine, which have pain-relieving properties.
·
Opioids: Opioids are substances that
includes natural, semi-synthetic, and synthetic drugs that act on the body's
opioid receptors. They can be derived from opium (like morphine and codeine),
semi-synthesized from opium alkaloids (like heroin), or entirely synthetic
(like fentanyl and pethidine).
CLASSIFICATION
1.
Natural opioids:
Morphine, Codeine
2.
Semi-synthetic opioids:
Oxycodone, Hydrocodone, Heroin
3.
Synthetic opioids:
Fentanyl, Methadone, Pethidine
MORPHINE
MOA:
Morphine's mechanism of action involves blocking calcium channels on presynaptic neurons, which in turn blocks the release of neurotransmitters such as substance P.
Additionally, morphine opens
potassium ion channels on postsynaptic
neurons, leading to repolarization (no
depolarization) and preventing further signal transmission.
PHARMACOLOGICAL ACTIONS:
1.
Central Nervous System (CNS):
·
Reduces visceral pain
·
Induces drowsiness
·
May produce a pleasurable floating
sensation
2.
Respiration:
·
Depresses the respiratory center
·
Overdose can lead to respiratory
depression, morphine poisoning, and potentially death
3.
Cardiovascular System:
·
Causes vasodilation
·
Reduces blood pressure (BP)
·
May result in bradycardia (slow heart
rate)
·
Reduces cardiac work
4.
Gastrointestinal Tract (GIT):
·
Reduces gastrointestinal motility
·
Reduces gastrointestinal secretion
5.
Smooth Muscle:
·
Can cause bronchoconstriction
(contraction of bronchial smooth muscle)
·
Induces contraction of the urinary
bladder
ADVERSE EFFECTS:
1.
Respiratory depression, which can lead
to death in cases of morphine overdose.
2.
Mental confusion and sedation.
3.
Hypotension (low blood pressure).
4.
Development of tolerance and dependence
with prolonged use.
5.
Allergic reactions, though these are
relatively rare, they can include symptoms such as rash, itching, and
difficulty breathing.
THERAPEUTIC USES:
1.
Analgesics:
Used for moderate to severe pain relief.
2.
Preanesthetics:
Can alleviate anxiety and provide pain relief before anesthesia.
3.
Antitussive agents:
Used to suppress severe coughing.
4.
Treatment of diarrhea:
Sometimes used for severe cases when other medications fail.
CONTRAINDICATIONS:
1.
Respiratory depression: Patients with
compromised respiratory function, such as severe asthma or chronic obstructive
pulmonary disease (COPD).
2.
Acute or severe bronchial asthma:
Morphine can worsen respiratory function in these patients.
DOSE AND ROUTE:
The typical dose of morphine ranges from 5 to 30 milligrams, administered orally or via injection (IV, IM & SC), every 4
hours as needed for pain relief.
ROLE OF NURSE:
1.
Assessment: Nurses evaluate pain level,
vital signs, medical history, and allergies before giving morphine.
2.
Education: Nurses inform patients and
families about morphine's purpose, dosage, side effects, and safety.
3.
Administration: Nurses give morphine as
prescribed, following safety guidelines.
4.
Monitoring: Nurses watch for adverse
reactions like respiratory depression or allergic responses and act swiftly if
needed.
5.
Documentation: Nurses keep detailed
records of morphine use, including dosage, patient response, and any issues.
DRUGS FOR
NEURODEGENERATIVE DISORDERS
NEURODEGENERATIVE DISORDERS
Neurodegenerative disorders are conditions
characterized by progressive damage to the nervous
system, leading to the worsening of neurons (nerve
cells) and ultimately impairing their functions.
Examples include Parkinson's disease &
Alzheimer's disease.
Alzheimer's disease: progressive memory loss and
cognitive decline.
Parkinson's disease: movement difficulties due to
dopamine neuron degeneration.
DRUGS FOR PARKINSON’S
DISEASE
- Dopaminergic
agents: Levodopa/carbidopa, dopamine agonists
- MAO-B
inhibitors: Selegiline, rasagiline
- COMT
inhibitors: Entacapone, tolcapone
- Anticholinergic
drugs: Benztropine, trihexyphenidyl
DOPAMINERGIC AGENTS
MOA:
Levodopa (L-DOPA):
Turns into dopamine, boosting dopamine
levels in the brain to alleviate Parkinson's symptoms.
Carbidopa:
Blocks an enzyme dopamine decarboxylase that
breaks down levodopa outside the brain,
allowing more levodopa to reach the brain and convert into dopamine, enhancing
its effectiveness in treating Parkinson's disease.
ADVERSE EFFECTS:
- Levodopa/carbidopa: Nausea, dyskinesias (involuntary movements), fluctuations in motor response.
USES:
- Levodopa/carbidopa:
treatment for Parkinson's disease to alleviate motor symptoms.
DOSE AND ROUTE:
Levodopa and carbidopa are usually taken orally, with the typical starting dose of levodopa being around 100
mg, gradually increasing to 200 mg or more per tablet. Carbidopa is
combined with levodopa at a ratio of 1:4,
often at a dose of 25 mg carbidopa per 100 mg
levodopa.
CONTRAINDICATIONS:
Common contraindications for levodopa and carbidopa
therapy include:
1.
Hypersensitivity: Patients with a known
hypersensitivity to levodopa, carbidopa, or any of the components of the
formulation should avoid its use.
2.
Non-selective monoamine oxidase (MAO)
inhibitors: Concurrent use of levodopa/carbidopa with non-selective MAO
inhibitors is contraindicated due to the risk of hypertensive crisis.
ROLE OF NURSE:
1.
Patient education on medication
administration and potential side effects.
2.
Monitoring for therapeutic response and
adverse reactions.
3.
Providing emotional support and
encouragement.
COMT INHIBITORS
MOA:
These drugs inhibit the
enzyme COMT (catechol-O-methyltransferase), which normally breaks down levodopa in the bloodstream. By
inhibiting COMT, these medications increase the
availability of levodopa in the brain, enhancing its effectiveness in
managing Parkinson's symptoms.
ADVERSE EFFECTS:
1.
Nausea
2.
Dyskinesias: Dyskinesias are
unintentional and irregular movements
3.
Orthostatic hypotension: Some
individuals may experience a drop in blood pressure upon standing (orthostatic
hypotension)
USES:
1. Enhance
effectiveness of levodopa therapy.
2. Treatment
of Parkinson’s disease
DOSE AND ROUTE:
Entacapone:
Typically administered orally, with a usual
dose of 200 mg taken with each
levodopa/carbidopa dose, up to a maximum of 8 doses per day.
CONTRAINDICATIONS:
Contraindications for COMT inhibitors:
1.
Hypersensitivity to the medication.
2.
Concurrent use with non-selective MAO
inhibitors.
ROLE OF NURSE:
The role of a nurse in the context of patients taking medications like COMT inhibitors involves:
1.
Educating patients on medication use.
2.
Monitoring for effects and side effects.
3.
Providing support and addressing
concerns.
4.
Collaborating with the healthcare team.
MAO-B INHIBITORS
MOA:
Monoamine oxidase-B (MAO-B) inhibitors act by
selectively inhibiting the enzyme monoamine oxidase
type B, which is responsible for the breakdown
of dopamine in the brain. By blocking this
enzyme, MAO-B inhibitors prevent the degradation of dopamine, thereby
increasing its availability.
ADVERSE EFFECTS:
1.
Gastrointestinal disturbances: Including
nausea, vomiting, and diarrhea.
2.
Insomnia: Difficulty falling asleep or
staying asleep.
3.
Hypotension: A sudden drop in blood
pressure, leading to dizziness or lightheadedness.
USES:
1.
Management of Parkinson's disease: MAO-B
inhibitors are used as adjunctive therapy to levodopa/carbidopa or dopamine
agonists to improve motor symptoms and overall function in Parkinson's disease
patients.
2.
Delaying disease progression: Some
evidence suggests that MAO-B inhibitors may have neuroprotective effects,
potentially slowing the progression of Parkinson's disease.
DOSE AND ROUTE:
Rasagiline:
Typically administered orally, with a usual
dose of 1 mg once daily
CONTRAINDICATIONS:
Common contraindications for MAO-B (monoamine
oxidase-B) inhibitors include:
1.
Hypersensitivity: Patients with a known
hypersensitivity to MAO-B inhibitors or any of the components of the medication
should avoid its use.
2.
Concurrent use with other MAO
inhibitors: MAO-B inhibitors should not be used concurrently with non-selective
MAO inhibitors (e.g., phenelzine, tranylcypromine) due to the risk of
hypertensive crisis.
ROLE OF NURSE:
In the context of patients taking medications like
MAO-B inhibitors, the role of a nurse involves:
1.
Guiding patients on medication
administration and potential side effects.
2.
Observing and documenting treatment
responses and adverse reactions.
3.
Offering guidance and addressing patient
queries or worries.
4.
Cooperating with healthcare peers to
ensure comprehensive patient care.
DRUGS FOR ALZHEIMER’S
DISEASE
1.
NMDA Receptor Antagonist: Memantine
2.
Cholinesterase Inhibitors: Donepezil,
Galantamine, Rivastigmine, Tacrine
MEMANTIDINE
MOA:
Memantine blocks NMDA receptors, preventing
excessive calcium influx into neurons and reducing excitotoxicity caused by
glutamate, thus protecting neurons from damage.
ADVERSE EFFECTS:
1.
Dizziness
2.
Headache
3.
Confusion
USES:
1.
Alzheimer's disease
2.
Vascular dementia (Vascular dementia is
a type of dementia that occurs when impaired blood flow to the brain leads to
cognitive decline)
DOSE AND ROUTE:
Memantine (oral tablets): The usual starting dose is
5 mg once daily, with gradual titration over several weeks to a target
maintenance dose of 10 mg twice daily (20 mg/day)
CONTRAINDICATIONS:
1.
Hypersensitivity to memantine or its
components.
2.
Severe renal impairment.
3.
Concurrent use with other NMDA receptor
antagonists.
ROLE OF NURSE:
1.
Educating patients on medication use.
2.
Monitoring for effects and side effects.
3.
Collaborating with the healthcare team.
CHOLINESTERASE INHIBITORS
MOA:
·
Block Enzyme:
Cholinesterase inhibitors (ChEIs) block the enzyme acetylcholinesterase (AChE).
·
Increase Acetylcholine:
This prevents the breakdown of acetylcholine
·
Boost Communication:
Higher acetylcholine levels improve communication between brain cells.
·
Enhance Memory and Cognition:
This helps improve memory and cognitive functions in Alzheimer's patients.
ADVERSE EFFECTS:
1. Nausea
2. Diarrhea
3. Muscle cramps
USES:
1.
Alzheimer's disease
2.
Myasthenia gravis
DOSE AND ROUTE:
1.
Donepezil:
·
Dose:
5-10 mg once daily (initial), can be increased to 23 mg once daily
·
Route:
Oral
2.
Rivastigmine:
·
Dose:
1.5-6 mg twice daily (oral), or 4.6-13.3 mg/24 hours (transdermal patch)
·
Route:
Oral, Transdermal
3.
Galantamine:
·
Dose:
4-12 mg twice daily (immediate-release), or 8-24 mg once daily
(extended-release)
·
Route:
Oral
CONTRAINDICATIONS:
Contraindications of Cholinesterase Inhibitors
1.
Bradycardia
2.
Peptic ulcer disease
3.
Asthma or chronic obstructive pulmonary
disease (COPD)
4.
Urinary tract obstruction
ROLE OF NURSE:
1.
Administer Medication:
Give cholinesterase inhibitors as prescribed.
2.
Educate Patients:
Explain medication purpose, dosage, and potential side effects.
3.
Monitor Patients:
Track their response to treatment and any adverse reactions.
4.
Collaborate with Team:
Work with other healthcare professionals for coordinated care.