Rimantadine

Rimantadine is an antiviral medicine that is used to prevent and treat infections caused by certain strains of influenza A virus. It can also be used in the treatment of influenza A virus infection in adults and children.

The mechanism of action of rimantadine is to inhibit replication of influenza A virus at early stages of its life cycle, thus preventing the spread of infection in the body. Rimantadine blocks the M2 ion channel of influenza A virus, which prevents virion depressurization inside host cells, necessary for the release of viral RNA and subsequent synthesis of viral proteins.

Rimantadine is recommended to be taken at the first symptoms of influenza for the most effective treatment. It can also be used as a preventive medicine during flu epidemics, especially among people at high risk of complications.

Although effective against influenza A virus, rimantadine may be less effective against some strains of the virus that show resistance to the drug. It is also not effective against influenza type B, which is also a frequent cause of seasonal influenza epidemics.

As with any drug, rimantadine may cause side effects, the most common of which are dizziness, impaired concentration, insomnia, nausea and dry mouth. The use of rimantadine should be supervised by a physician, especially in persons with existing kidney, liver or cardiovascular disease.

Indications Rimantadine

1. Influenza Prevention: Rimantadine is used to prevent influenza type A in adults and children. It is particularly recommended for high-risk individuals (e.g., the elderly, people with chronic illnesses, health care workers, etc.) and during periods of influenza outbreaks.
2. Flu Treatment: Rimantadine is used to treat influenza type A in adults and children, helping to shorten the duration of illness and reduce the severity of symptoms. Treatment is most effective if the drug is started within the first 1 to 2 days after symptoms appear.

Release form

1. Tablets: The most common form of rimantadine, suitable for adults and children over a certain age specified in the instructions for use. Tablets usually contain 50 mg of the active substance.
2. Capsules: Similar to tablets, contain 100 mg of rimantadine. Capsules are intended for oral administration and provide a convenient dosage for adults.
3. Syrup (oral solution): Suitable for children and adults who have difficulty swallowing tablets or capsules. The syrup makes it easier to customize the dosage, especially when treating children.

Pharmacodynamics

1. Inhibits influenza A virus replication: Rimantadine acts by binding to the influenza A virus membrane protein (M2 channel), which prevents it from replicating in infected cells.
2. Blocks virus entry into the cell: Rimantadine blocks the virus release process from the early endosomal compartment of the infected cell, thereby preventing its entry into the cytoplasm.
3. Prophylacticeffect: Prophylactic use of rimantadine reduces the risk of influenza infection in people in contact with infected persons.
4. Treatment of influenza: Rimantadine is also effective in treating influenza type A in adults and children. It reduces the duration and severity of flu symptoms if started within the first 48 hours after the onset of illness.
5. Selectivity of action: Rimantadine acts predominantly against influenza A virus, while influenza B virus is resistant to its effects.
6. Mechanism of resistance: Although rimantadine is an effective antiviral agent, the emergence of resistance to it may occur due to mutations in the M2 gene of influenza A virus.

Pharmacokinetics

1. Absorption: Rimantadine is well absorbed from the gastrointestinal tract after oral administration. It usually begins to take effect within 2-4 hours after ingestion.
2. Distribution: Rimantadine has high affinity to blood plasma proteins, which leads to its distribution in various tissues of the body. It also penetrates the blood-brain barrier.
3. Metabolism: Most of the rimantadine is metabolized in the liver by demethylation and hydroxylation.
4. Excretion: Rimantadine and its metabolites are excreted mainly through the kidneys. In patients with impaired renal function there may be delays in excretion of the drug, therefore dosage adjustment may be required.
5. Half-life: The half-life of rimantadine is about 25 hours in adults and up to 34 hours in elderly patients.
6. Systemic exposure: Rimantadine exerts its effect by blocking viral M2-ionic tubule protein, which prevents the spread of influenza type A.
7. Interactions: Rimantadine may interact with other medicines, therefore, before its use in combination with other drugs it is necessary to consult a doctor.

Dosing and administration

The following are general recommendations, but you should always follow your doctor's instructions and directions for use.

For adults (prevention and treatment of influenza type A):

• Prophylaxis: 100 mg (usually one tablet) once daily.
• Treatment: 100 mg twice daily for 5 days. Treatment is most effective when started within the first 48 hours after the onset of symptoms.

For the kids:

The dosage for children depends on their age and body weight. It is important to consult your pediatrician to determine the exact dose. As a general guideline:

• Forchildren 1 to 10 years of age, 5 mg per kg of body weight per day divided into two doses, but no more than 150 mg per day, is usually prescribed for the treatment of influenza.
• Children over 10 years of age and weighing more than 50 kg may take the adult dose.

Special Instructions:

• Rimantadine should be taken after meals to reduce the risk of gastrointestinal side effects.
• It is important to drink enough fluids during treatment with rimantadine.
• The duration of administration for prophylaxis may be increased depending on the influenza virus situation in the environment on the advice of a physician.

Use Rimantadine during pregnancy

Rimantadine is used for the prevention and treatment of influenza type A. However, its use during pregnancy may be limited or recommended only in strict indications.

To date, data on the safety of rimantadine during pregnancy are limited. This is due to the fact that conducting controlled clinical trials in pregnant women is generally unacceptable for ethical reasons.

Rimantadine is an FDA Category C drug, which means that it has evidence of adverse effects on fetal development in animals, but there are not enough human studies. Use of rimantadine during pregnancy should be based on careful discussion of the benefits of treatment and potential risks to the mother and fetus with your doctor.

Contraindications

Here are a few contraindications for its use:

1. Hypersensitivity: People with known hypersensitivity to rimantadine or other ingredients of the drug should not use it.
2. Renal insufficiency: Rimantadine is excreted through the kidneys, therefore its use may be undesirable in patients with impaired renal function or chronic renal insufficiency.
3. Pediatric age: The use of rimantadine is not recommended in children under 1 year of age without medical advice. In children under 10 years of age, rimantadine should be used only when prescribed by a doctor.
4. Pregnancy and lactation: The safety of rimantadine use during pregnancy or lactation has not been established, therefore its use in these cases should be carried out under medical supervision.
5. Heart disease: Rimantadine may increase unwanted cardiovascular side effects, therefore its use should be used with caution in patients with cardiovascular disease.
6. Central Nervous System: Rimantadine may cause nervous side effects such as dizziness and restlessness, so it should be used with caution in patients with central nervous system disorders.

Side effects Rimantadine

1. Gastrointestinal disorders: Including nausea, vomiting, diarrhea, anorexia, and dyspepsia (digestive disorders).
2. Nervous system: Headache, weakness, insomnia, anxiety, and rarely hallucinations, anxiety, confusion and seizures may occur.
3. Allergic reactions: Allergic reactions in the form of skin rash, itching, urticaria, angioedema and anaphylactic shock may occur.
4. Cardiac effects: In some cases, heart rhythm disturbances such as arrhythmias may occur.
5. Other reactions: Asthenia (weakness), sweating, fatigue, dry mouth, redness of the skin, and joint pain may also occur.

Overdose

1. Central Nervous System (CNS): Symptoms associated with CNS agitation such as restlessness, insomnia, headache, dizziness, irritability, anxiety and hallucinations may occur.
2. Gastrointestinal tract: Digestive-related symptoms such as nausea, vomiting, abdominal pain, diarrhea, and anorexia may occur.
3. Cardiovascular system: In rare cases heart rhythm disturbances, including tachycardia, arterial hypertension or hypotension, may occur.
4. Respiratory system: Symptoms related to breathing, such as difficulty breathing or gasping, may occur.
5. Other symptoms: Symptoms such as seizures, hyperthermia (increased body temperature), and allergic reactions may occur.

Interactions with other drugs

1. Anticholinergic drugs: When combined with drugs such as anticholinergic agents, additional anticholinergic effects such as dry mouth, constipation, and visual disturbances may occur.
2. Centrally acting drugs: Rimantadine may increase the sedative effects of centrally acting drugs such as sleeping pills, antidepressants, and pain relievers.
3. Drugs that increase the risk of arrhythmias: Rimantadine may increase the QT interval and increase the risk of arrhythmias, especially when used concomitantly with other drugs that also affect the QT interval, such as antiarrhythmic agents (e.g., amidarone, quinidine) and antibiotics (e.g., erythromycin, azithromycin).
4. Drugs metabolized through the cytochrome P450 system: Rimantadine may affect the activity of cytochrome P450 enzymes in the liver, which may alter the metabolism of other drugs such as anticoagulants, antipsychotics, antidepressants and antiepileptics.
5. Drugs that inhibit renal cation excretion: Rimantadine may compete with other drugs that can also be excreted by the kidneys, which may increase their blood concentrations and increase the risk of toxicity.