Symmetrel 100 mg Capsules

Brand name

The trade name of the drug is Symmetrel. This is the registered name under which the drug is known in medical practice and is available in pharmacies.

International Nonproprietary Name (INN)

The international nonproprietary name is amantadine. It denotes the active active ingredient and is used internationally in pharmacology.

Form of release

Simmetrel is available in two forms: capsules of 100 mg, packed in blisters of 10 pieces or bottles of 100 capsules, and syrup with a concentration of 50 mg/5 ml in 150 ml bottles with a measuring spoon. The capsules have white or slightly grayish color, and the syrup has a clear consistency with a slight fruity aroma, which facilitates its use in children and patients with swallowing difficulties.

Composition

Active substance

The main active ingredient is amantadine hydrochloride. One capsule contains 100 mg of amantadine hydrochloride, and 5 ml of syrup contains 50 mg.

Auxiliary Components

The capsules include lactose monohydrate, microcrystalline cellulose, magnesium stearate, and the shell consists of gelatin and titanium dioxide. The syrup contains sorbitol, sucrose, methylparaben, propylparaben (preservatives), citric acid, sodium citrate, cherry flavoring, and purified water.

Pharmacologic Properties

Pharmacodynamics

Amantadine, the active ingredient of Symmetrel, has a dual mechanism of action: antiviral and neurotropic. As an antiviral agent, amantadine blocks M2 ion channels of influenza A virus, preventing the release of viral RNA into the cytoplasm of infected cells. This disrupts the replication process of the virus, reducing its spread in the body. The antiviral effect is most pronounced when treatment is started within 48 hours of the onset of flu symptoms, shortening the duration of the illness and reducing the severity of manifestations.

As an antiparkinsonian agent, amantadine acts on the central nervous system by increasing the release of dopamine from presynaptic terminals and inhibiting its reuptake. It also has a weak antagonistic effect on NMDA receptors, which helps to reduce rigidity, tremor, and bradykinesia in Parkinson's disease. The therapeutic effect in Parkinsonism is noticeable in 2-7 days, peaking in 1-2 weeks. Symmetrel does not cure Parkinson's, but it significantly improves motor function and quality of life in patients.

Pharmacokinetics

Absorption

Amantadine is well absorbed from the gastrointestinal tract after oral administration. Maximum plasma concentrations are reached after 1-4 hours for capsules and 2-3 hours for syrup. Bioavailability is about 60-90%, and food intake does not significantly affect absorption, which allows taking the drug independently of meals.

Distribution

Amantadine binds weakly to plasma proteins (about 67%), mainly to albumin. The volume of distribution is about 3-8 l/kg, indicating penetration into various tissues, including the central nervous system, lungs and salivary glands. The drug passes through the blood-brain barrier, providing its neurotropic effect, and is also excreted in breast milk.

Metabolism

Amantadine is metabolized to a minimal extent (less than 10%) in the liver. The bulk of the substance is excreted unchanged, which distinguishes it from many other drugs. A small amount is metabolized to N-acetylamantadine, which has no significant pharmacological activity.

Excretion

The half-life of amantadine is 10-31 hours (average 15 hours) in patients with normal renal function. The drug is excreted mainly through kidneys (about 90% in unchanged form) by tubular filtration and tubule secretion. Complete excretion takes about 3-5 days, but in case of renal dysfunction this period increases.

Indications for Use

Simetrel is indicated for the treatment of the following conditions:

• Influenza A (prevention and treatment in adults and children);
• Parkinson's disease (idiopathic or secondary);
• Parkinsonism caused by taking neuroleptics or other causes;
• Extrapyramidal side effects of antipsychotic drugs;
• Fatigue in multiple sclerosis (in some cases).

The drug is effective in controlling symptoms and preventing viral infections.

Contraindications

The use of Simetrel is prohibited in:

• Hypersensitivity to amantadine or auxiliary components;
• Severe renal insufficiency (creatinine clearance less than 10 ml/min);
• Epilepsy or history of seizures;
• Severe heart failure or arrhythmias;
• Pregnancy (first trimester) and lactation;
• Children under 1 year of age.

Cautious prescribing in glaucoma, psychosis, hepatic dysfunction.

Method of Administration and Dosage

How to take

Symmetrel capsules are taken orally, drinking water (100-150 ml), regardless of meals. Syrup is measured with a spoon and taken orally, preferably in the morning and afternoon to avoid insomnia. Capsules should not be chewed or opened to preserve the stability of the active ingredient.

Dosages for adults and children

Adults

Flu: 100 mg once daily for 4-5 days (treatment) or 10-14 days (prophylaxis). In Parkinson's: 100 mg once daily for 3 days, then 100 mg twice daily, up to a maximum of 400 mg/day, course determined by a doctor.

Children over 1 year of age

In influenza: 1-9 years - 2-4 mg/kg body weight per day (maximum 100 mg); 10-12 years - 100 mg 1 time per day. In Parkinson's in children is not used.

Dose adjustment in certain conditions

In renal insufficiency: creatinine clearance 30-50 ml/min - 100 mg every other day; 15-29 ml/min - 100 mg once every 7 days. In hepatic insufficiency correction is not required, but monitoring of the condition is necessary.

Side Effects

Possible adverse reactions include:

• Nervous system: insomnia, anxiety, dizziness, hallucinations;
• Gastrointestinal system: nausea, dry mouth, decreased appetite;
• Cardiovascular system: orthostatic hypotension, tachycardia;
• Urinary system: urinary retention, edema;
• Allergic reactions: rash, itching, urticaria;
• Other: confusion, livedo reticularis (reticular pigmentation).

Side effects are more common in the elderly and require monitoring.

Overdose

Symptoms of overdose

Doses above 400-600 mg/day may cause agitation, convulsions, arrhythmias, hypotension, hallucinations.

First aid measures

Stop taking, call an ambulance. Gastric lavage, give activated charcoal. Symptomatic treatment in hospital is required.

Drug Interactions

Influence on the effect of other drugs

Simmetrel enhances the effects of anticholinergics and levodopa, increasing the risk of side effects. Alcohol and CNS stimulants increase agitation. Diuretics (triamterene) reduce the excretion of amantadine.

Compatibility with alcohol and food

Alcohol increases CNS side effects. Food does not affect absorption.

Special Precautions

Use in pregnancy and breastfeeding

Simetrel is contraindicated in the first trimester; in the second and third trimesters by strict indications. Lactation is prohibited due to penetration into milk.

Effects on driving and mechanisms

The drug may cause dizziness and hallucinations, which requires caution when driving.

Particularities of use in elderly people and children

In the elderly, the dose is reduced in case of impaired renal function. In children under 1 year of age do not use; older - with regard to body weight.