Rasagiline

Introduction Overview

Generic Name

rasagiline

Brand Name

Azilect

Dosage Form

oral tablet

Drug Class

Dopaminergic antiparkinsonism agents, selective MAO-B inhibitor

Pharmacokinetics

Absorption

Rasagiline is rapidly absorbed following oral administration, with peak plasma concentrations typically reached within 0.5 to 2 hours. The extent of absorption is not significantly affected by food intake, although the time to peak concentration may be delayed slightly with high-fat meals. Its bioavailability, however, is limited due to significant first-pass hepatic metabolism. Clinical studies report an absolute bioavailability of approximately 36%. The rate and extent of absorption are consistent across different patient populations, though caution is advised in hepatic impairment where metabolism may be altered.

Distribution

Once absorbed, rasagiline exhibits moderate plasma protein binding, estimated around 85%, primarily to albumin. It has a large apparent volume of distribution, indicating extensive tissue penetration, including central nervous system penetration critical for its therapeutic effect in Parkinson’s disease. The drug’s lipophilicity facilitates crossing the blood-brain barrier efficiently. Distribution may be influenced by factors such as age, disease state, and concomitant medications; however, significant alterations have not been identified within typical therapeutic dosing.

Metabolism

Rasagiline is extensively metabolized in the liver predominantly by CYP1A2 enzymes through oxidative pathways, forming inactive metabolites such as aminoindan. The metabolic process involves N-dealkylation and aromatic hydroxylation, resulting in pharmacologically inactive compounds excreted renally. The CYP1A2-mediated metabolism is influenced by genetic polymorphisms and inhibitors or inducers of CYP1A2, potentially altering plasma rasagiline concentrations and necessitating dose adjustments. The lack of active metabolites confers a straightforward pharmacodynamic profile.

Elimination

Elimination of rasagiline and its metabolites occurs primarily via the kidneys, with approximately 90% recovered in urine mostly as inactive metabolites, and a minor fraction eliminated in feces. The terminal half-life ranges from 1.5 to 3 hours in healthy adults but may be prolonged in hepatic impairment. The clearance rate is significantly influenced by liver function, warranting careful monitoring in patients with hepatic disease. Renal impairment has less impact due to the elimination of inactive metabolites.

Dosage Forms

Adults

For treatment of Parkinson’s disease symptoms, rasagiline is commonly administered orally as 0.5 mg to 1 mg once daily. In monotherapy, the recommended dose is 1 mg once daily. When adjunctive therapy with levodopa is required, dosing may start at 0.5 mg daily with titration to 1 mg daily based on clinical response and tolerability. Regular assessment for efficacy and adverse reactions is essential. Maximum recommended dose is 1 mg daily to avoid increased risk of adverse effects.

Adolescents

There is limited clinical data on the use of rasagiline in pediatric populations and it is not generally recommended for adolescents. The safety and efficacy for Parkinson’s disease in pediatric patients have not been established. Use is reserved for adult patients unless decided by specialist consultation under strict monitoring.

Special Populations

In patients with hepatic impairment, dosing should be approached cautiously because rasagiline metabolism is primarily hepatic. Severe hepatic impairment is a contraindication due to the risk of drug accumulation and toxicity. No specific dose adjustment is recommended in mild to moderate renal impairment, as rasagiline metabolites are inactive and renally cleared. Geriatric patients do not require dosage adjustment but may be more sensitive to side effects. Caution advised in patients with cardiovascular diseases due to potential blood pressure changes. Pregnancy and breastfeeding: safety not established; use only if potential benefits justify risks.

Mechanism Of Action

Rasagiline exerts its therapeutic effects primarily through irreversible inhibition of monoamine oxidase B (MAO-B), an enzyme responsible for the catabolism of dopamine in the brain. By selectively inhibiting MAO-B, rasagiline increases extracellular dopamine concentrations in the striatum, thereby enhancing dopaminergic neurotransmission which alleviates motor symptoms associated with Parkinson’s disease. This selective inhibition spares MAO-A, minimizing the risk of hypertensive crises from dietary tyramine intake compared to nonselective MAO inhibitors.

At the molecular level, rasagiline binds covalently to the flavin adenine dinucleotide cofactor at the active site of MAO-B, leading to sustained inhibition until new enzyme molecules are synthesized. This irreversibility contributes to prolonged clinical effects beyond the presence of the drug in plasma. Cellular pathways modulated include the dopaminergic nigrostriatal pathway, which is deficient in Parkinson’s disease due to dopaminergic neuron degeneration.

Beyond its MAO-B inhibition, rasagiline has demonstrated neuroprotective properties in preclinical studies. It may exert antiapoptotic effects by modulating mitochondrial permeability transition pores, promoting neuronal survival by reducing oxidative stress and mitochondrial dysfunction. Clinical trials suggest these neuroprotective effects may slow disease progression, although definitive evidence in humans remains under evaluation.

Compared to other dopaminergic agents, such as levodopa or dopamine agonists, rasagiline provides symptomatic relief as a monoamine oxidase inhibitor rather than replacing dopamine directly. Its mechanism allows for adjunctive use to potentiate levodopa effects and reduce motor fluctuations. Its selective MAO-B inhibition distinguishes it from selegiline, with a similar mechanism but different metabolic profiles and side effect spectrum.

Pharmacological Actions

Selective irreversible inhibition of monoamine oxidase B (MAO-B) enzyme
Increase in extracellular brain dopamine concentration due to decreased dopamine metabolism
Enhancement of nigrostriatal dopaminergic neurotransmission
Potential neuroprotective effects via antiapoptotic mechanisms
Reduction of oxidative stress in neuronal mitochondria
Adjunctive improvement of motor function in Parkinson’s disease
Minimal interaction with MAO-A at therapeutic doses, reducing tyramine sensitivity
Improvement of motor symptoms such as rigidity, tremors, and bradykinesia
Modulation of mood and cognitive effects related to dopaminergic pathways
Long duration of enzyme inhibition despite short plasma half-life

Therapeutic Clinical Uses

Management of idiopathic Parkinson’s disease as monotherapy in early stages
Adjunct therapy with levodopa for motor symptom control in advanced Parkinson’s disease
Reduction of motor fluctuations in patients on long-term levodopa therapy
Improvement of motor function, including rigidity, tremor, and bradykinesia
Potential use to delay the need for dopaminergic replacement therapy
Symptomatic treatment of stiffness, spasms, and poor muscle control
Clinical use in patients intolerant to dopamine agonists
Off-label use investigated for neuroprotection in Parkinsonian syndromes
Adjunctive therapy to potentially reduce levodopa dosage requirements

Side Or Adverse Effects

Depressed mood and behavioral changes such as hallucinations or mood swings
Insomnia and sleep disturbances including vivid dreams and daytime sleepiness
Involuntary muscle movements (dyskinesias), especially when used with levodopa
Gastrointestinal symptoms including nausea, vomiting, indigestion, and constipation
Loss of appetite and weight loss
Joint pain and stiffness
Skin rash and hypersensitivity reactions
Dry mouth and nasal congestion
Peripheral edema (swelling in hands or feet)
Serious risk of serotonin syndrome when combined with serotonergic agents
Hypotension or dizziness, especially on standing (orthostatic hypotension)
Excessive daytime sleepiness and sudden sleep onset episodes
Increased sexual urges or impulse control disorders (e.g., gambling)
Severe headache and hypertensive episodes related to food or drug interactions
Allergic reactions including anaphylaxis (rare)

Precautions

Do not use with other monoamine oxidase inhibitors within 14 days due to risk of hypertensive crisis
Avoid consuming foods high in tyramine such as aged cheeses, fermented meats, and soy products to prevent hypertensive episodes
Monitor patients carefully for signs of serotonin syndrome when combined with antidepressants or serotonergic drugs
Use caution in patients with hepatic impairment due to metabolism pathways
Avoid abrupt discontinuation to prevent withdrawal symptoms and worsening of Parkinson’s symptoms
Be cautious in patients with a history of cardiovascular disease or uncontrolled hypertension
Advise patients about potential for drowsiness and dizziness; caution advised during driving or operating machinery
Inform patients about the possibility of impulse control disorders and unusual urges while taking the drug
Evaluate for skin lesions regularly due to increased risk of melanoma in Parkinson’s disease patients
Warn about possible interactions with over-the-counter cough medicines, muscle relaxants, and herbal supplements like St. John’s Wort
Monitor elderly patients closely as they might have increased sensitivity to side effects
Assess nutritional status and gastrointestinal symptoms periodically to address appetite or weight changes
Advise patients to report mood changes, hallucinations, or unusual behaviors promptly
Use cautiously in patients with renal impairment although no dose adjustment typically required

Warnings

Contraindicated in patients who have used other MAO inhibitors within the past 14 days
Potentially fatal drug interactions with sympathomimetic amines, certain antidepressants, opioids, and serotonergic drugs
Risk of hypertensive crisis if tyramine-containing foods are ingested during therapy or within two weeks of cessation
Possible sudden onset of sleep episodes during normal activities in patients on concomitant levodopa therapy
Risk of serotonin syndrome manifesting as agitation, hallucinations, muscle stiffness, and autonomic instability
May impair alertness and reaction time, affecting safe operation of vehicles or machinery
Not recommended in severe hepatic impairment due to altered metabolism and increased toxicity risk
Risk of worsening Parkinsonian symptoms or uncontrolled muscle movements
Warning for mood changes including depression and suicidal ideation
Potential for cardiovascular events in predisposed patients
Use with caution during pregnancy and breastfeeding due to unknown safety profile
Increased risk of skin cancer (melanoma) observed in Parkinson’s disease mandates regular dermatologic evaluations
May cause orthostatic hypotension leading to falls or syncope

Contraindications

Hypersensitivity or allergy to rasagiline or any component of the formulation
Use of any other monoamine oxidase inhibitors (MAOIs) within 14 days prior to starting rasagiline
Concurrent use with sympathomimetic agents (e.g., meperidine, methadone) due to risk of hypertensive crisis or serotonin syndrome
Concomitant use with certain antidepressants, such as SSRIs, SNRIs, tricyclics, or other serotonergic agents without physician supervision
Severe hepatic impairment due to impaired metabolism and increased risk of adverse effects
Use with linezolid, methylene blue injection, or other reversible inhibitors of MAO-A which increase serotonin levels
Patients with a history of hypersensitivity reactions to similar MAO-B inhibitors like selegiline
Known or suspected pregnancy or breastfeeding unless benefits outweigh risks
Use in pediatric patients generally contraindicated due to lack of established safety and efficacy

Drug Interactions

Contraindicated with monoamine oxidase inhibitors, including isocarboxazid, phenelzine, tranylcypromine, selegiline, and linezolid
Risk of serotonin syndrome with concomitant use of serotonergic drugs such as SSRIs, SNRIs, tricyclic antidepressants, lithium, tramadol, dextromethorphan, and St. John’s Wort
Increased risk of hypertensive crisis with sympathomimetic drugs including meperidine, methadone, cyclobenzaprine
Interactions with levodopa-containing products may increase dopaminergic side effects such as dyskinesia
CYP1A2 inhibitors (e.g., ciprofloxacin, fluvoxamine) can increase rasagiline plasma concentration, requiring dosage adjustment
Effects potentiated by other CNS depressants like opioid analgesics, benzodiazepines, and alcohol
Potential interaction with anticoagulants and antiplatelet agents requiring careful monitoring
Additive hypotensive effects when used with antihypertensive agents
Drugs inducing CYP1A2 may decrease rasagiline efficacy due to increased metabolism
Avoid combination with methylene blue as it may precipitate serotonin syndrome or hypertensive crisis
Interactions with stimulant drugs used in ADHD or narcolepsy that may raise blood pressure or risk serotonin syndrome
Potential for potentiation of dopaminergic side effects with other antiparkinsonian agents
Avoid co-administration with St. John's Wort due to serotonergic interaction risk
Concurrent use with over-the-counter cough medications containing dextromethorphan may provoke adverse reactions

Preparations Of The Drug

Oral tablets containing rasagiline mesylate
Dosage strengths: 0.5 mg and 1 mg tablets
Available as branded formulation under the trade name Azilect
Tablets intended for once-daily oral administration
Supplied in blister packs or bottles depending on manufacturer
Tablets are film-coated for ease of swallowing and taste masking
Generic forms of rasagiline available as equivalent oral tablets
No injectable or transdermal formulations currently marketed
Tablets stored at controlled room temperature away from moisture and heat
Packaging includes patient information leaflets detailing usage and precautions