Key Facts Comparing Amantadine With Rimantadine

Rimantadine

Mechanism of action:

• Inhibit the viral membrane M2 matrix proteins that function ashydrogen ion channels. These channels are required for thefusion of viral membrane to host cell membrane to form endosomes via endocytosis. These channels are also required to provide acidic environment necessary for viral uncoating.
• Interferes with the release of new virions.

Adverse effects:

• Nausea and vomiting
• Diarrhea
• Dyspepsia
• Abdominal pain
• Xerostamia
• Anorexia
• Headache
• Insomnia
• Taste alterations
• Impaired concentrations
• Nervousness
• Dizziness
• Asthenia
• Ataxia
• Bronchospasms
• Depression
• Skin rash
• Tinnitus
• Cardiac failure
• Heart block

Therapeutic uses:

• Prophylaxis and treatment of influenza A

Pharmacokinetics:

• Rapid gastrointestinal absorption after oral administration, with 6 hours duration to achieve peak blood concentration
• Does not readily penetrate CNS through blood-brain barrier compared to amantadine, thus less CNS adverse effects
• 40% bounded to plasma proteins, mainly albumin
• Extensive hepatic metabolism
• Renal excretion 

Drug interactions:

• Live influenza virus vaccines

Special precautions:

• Renal impairment
• Hepatic impairment
• Epileptic or other seizure disorders patients
• Psychosis
• Pregnancy
• Elderly

Contraindications:

• Hypersensitivity

Adminidstration:

• Oral

Pregnancy class:

• C

Amantadine

Mechanism of action:

• Inhibit the viral membrane M2 matrix proteins that function as hydrogen ion channels. These channels are required for the fusion of viral membrane to host cell membrane to form endosomes via endocytosis. These channels are also required to provide acidic environment necessary for viral uncoating.
• Interferes with the release of new virions.

Adverse effects:

• Seizures
• Psychosis
• Ataxia
• Hallucinations
• Heart failure
• Depression
• Orthostatic / Postural hypotension
• Blood dyscrasias
• Urinary retention
• Irritability
• Gastrointestinal disturbances
• Anorexia
• Livedo reticularis
• Ankle edema
• Congestive heart failure
• Convulsions
• Cardiac arrest (overdosage)

Therapeutic uses:

• Influenza A treatment and prophylaxis
• Herpes zoster infections in immunocompromised patients
• Parkinson's 

Pharmacokinetics:

• Rapid GIT absorption after oral administration
• Cross placenta and breast milk
• 67% bounded to plasma protein
• Cross blood-brain barrier and readily penetrate CNS
• Lower hepatic metabolism
• Excreted via urine by glomerular filtration and tubular secretion, mostly as unchanged metabolite and less acetylated forms

Drug interactions:

• Enhances the adverse effects of antimuscarinics, levodopa, CNS stimulants and drugs that increase urinary pH

Special precautions:

• Renal impairment
• Patients with cardiovascular or liver diseases
• Recurrent eczema
• Withdrawal of amantadine from the elderly (should be gradual)

Contraindications:

• Gastric ulcerations
• Hypersensitivity
• Pregnancy and lactating
• Epileptic or other seizure disorders
• Severe renal impairment

Administration:

• Oral, should be taken with food

Pregnancy class:

• C