Methsuximide for Absence Seizures - A Comprehensive Overview

Overview

Methsuximide is an anticonvulsant or anti-epileptic drug used for the treatment of absence seizures or petit mal seizures (it causes sudden and brief lapses in one’s attention). The drug may be used alone or in combination with other anticonvulsant drugs to treat absence seizures. It was approved by the United States Food and Drug Administration (USFDA) in 1957 for treating absence seizures alone or along with other antiepileptic drugs. However, it is no longer commonly used and is still available nowadays. Ethosuximide is used as a first-line treatment for absence seizures, replacing Methsuximide. This article talks in detail about Methsuximide, its indications, side effects, drug dosage, contraindications, clinical pharmacology, warnings and precautions, and drug reactions.

Drug Group:

The drug belongs to a class of anticonvulsant (anti-epileptic) drugs that are derivatives of succinimide. Its chemical formula is N,2-dimethyl-2-phenyl succinimide.

Indications

The drug is used for treating petit mal or absence seizures, which are characterized by sudden and brief lapses in consciousness or attention.

Dose Form and Strength:

Capsule (Oral): 150 mg (milligrams) and 300 mg.

For Patients:

What Are Absence Seizures?

It is also called petit mal seizures. It is a subtype of seizures sudden and brief lapses in attention. This condition is usually more common in children than adults. The affected person may be staring at a particular space for some time. Symptoms also include eyelid fluttering, lip smacking, and chewing motions.

What Is Methsuximide Prescribed For?

Methsuximide is prescribed to treat the absence of seizures or petit mal seizure, which causes a person to lose awareness for a short duration and they do not respond to others or stare at one place. The drug decreases abnormal brain activity and is used when anticonvulsants and other medicines are ineffective in treating absence seizures.

How Should Methsuximide Be Used?

The drug is available in capsule form, to be taken orally, one or multiple times. The medicine should be taken simultaneously daily, as prescribed by the pharmacist or doctor, or by following the label instructions. The doctor must be contacted if any part of the instructions is unclear to the person. Also, the drug should be taken as directed. One should not alter the drug dose and frequency of intake without consulting their doctor.

The healthcare provider may start on a low dose of Methsuximide and later increase the dosage once a week.

The drug does not treat the condition (absence of seizures) but can only cure it. The drug should only be stopped by asking the doctor, even if a person starts feeling better. Quitting the drug suddenly may cause side effects and worsening of the seizures. The doctor usually decreases the drug dosage gradually.

What Precautions Should Be Followed Before Taking Methsuximide?

• The doctor must be informed about allergic reactions to the drug, its ingredients, or any other drug.

• One must also inform the doctor about any past or present medical history, such as kidney or liver disease or mental illnesses.

• The person should also tell the doctor about all the non-prescription and prescription drugs that one is taking or planning to take. These include herbal products, nutritional supplements, and vitamins. In addition, one must also reveal about antidepressants if they are taking them. The doctor may need to change the drug dosage or monitor the patient for side effects.

• They must also inform the doctor about taking Methsuximide, including dental procedures, if undergoing surgery.

• If a person is pregnant, planning to get pregnant, breastfeeding, or getting pregnant while taking Methsuximide, inform the doctor immediately.

• The medicine causes drowsiness or dizziness. Therefore, one should avoid operating heavy machinery or driving a car while taking Methsuximide. Also, alcohol must be avoided with this drug, as it adds to the drowsiness effects. One should contact the doctor to know about the safe use of alcohol while taking the drug.

• The drug is also known to cause changes in the mental health of a person, such as the occurrence of suicidal thoughts (planning to kill or harm oneself), panic attacks (sudden episodes of anxiety and fear), agitation (a state of nervous restlessness or excitement), depression (prolonged sadness), or stress (excessive worry). Therefore, the person or the caregivers must contact the healthcare provider immediately if the person experiences any such symptoms of mental health.

What Are the Side Effects of Methsuximide?

Common side effects:

• Constipation.

• Nausea.

• Diarrhea.

• Vomiting.

• Weight loss.

• Headache.

• Loss of appetite.

• Stomach pain.

• Hiccups.

• Confusion.

• Drowsiness.

• Slow thinking.

• Blurred vision.

• Swollen eyes.

• Dizziness.

• Drowsiness.

• Sensitivity to light.

• Problems with coordinating movements.

• Fear or developing severe illnesses.

Serious Side Effects:

• Muscle pain.

• Blisters.

• Hives.

• Swelling and pain in joints.

• Itchy rash and redness on the face.

• Fever, sore throat, chills.

• Unknown fever.

Drug Dosage and Administration

Adult Drug Dose:

The recommended drug dosage of Methsuximide is 300 milligrams (mg) per day for the initial week. After that, the dosage can be increased by 300 mg (milligrams) at weekly intervals for at least three weeks, followed by a daily drug dosage of 1.2 grams. The treatment is, however, individualized depending on the patient’s response and tolerance to Methsuximide.

Pediatric Drug Dose:

150 mg (milligrams), a small capsule, is usually recommended for young children.

Overdose

Suppose a person has a drug overdose with Methsuximide. In that case, they must contact the poison control department, or in case the victim has seizures, collapses, or has troubled breathing, then the nearest emergency services must be contacted immediately.

Treatment of Overdose:

The treatment for drug overdose from Methsuximide is usually supportive, along with gastric lavage, emesis, cathartics, and activated charcoal. The metabolites (N-desmethyl) of Methsuximide may be removed with charcoal hemoperfusion.

Missed Dose

In case one misses the drug dosage of Methsuximide, the person must take it as soon as it is remembered. However, if it is already time for the next scheduled dose, one must skip the missed drug dose and continue with the next one. Do not take a double dose in such a case to compensate for the missed one.

Drug Storage and Disposal

The drug should be stored in an airtight container and away from children. It must be stored at a room temperature between 25 to 30 degrees Celsius (59 to 86 degrees Fahrenheit) and away from excess heat and moisture.

Unneeded or expired medicine doses of Methsuximide must be discarded safely to ensure that someone else does not consume them accidentally. The drug should not be flushed into the toilets; rather, it should be discarded through a take-back program by contacting the nearest garbage or recycling department or pharmacist. However, if one does not have access to take-back programs, they can discard the medicine by following the FDA (Food and Drug Administration) guidelines for safe drug disposal given on their website.

For Doctors

Clinical Pharmacology:

Mechanism of Action and Pharmacodynamics

The drug binds to T-type voltage-sensitive calcium channels, which help mediate the entry of calcium ions into excitable cells and are also involved in various calcium-dependant processes, such as hormone or neurotransmitter release, muscle contraction, cell division and cell death, cell motility, and gene expression.

The drug suppresses the three-cycle (paroxysmal) per second spike and wave activity that is associated with lapses of consciousness, commonly seen in absence (petit mal) seizures. The epileptic attacks get reduced eventually by the motor cortex and depression, and elevation of the central nervous system threshold to convulsive stimuli.

Pharmacokinetics

• Absorption: Following oral administration, the drug is rapidly absorbed in the body. It takes one to four hours to reach the maximum concentration (Tmax).

• Distribution: The volume of distribution is 0.65 L/kg.

• Metabolism: The drug gets rapidly metabolized into the liver from demethylated to N-desmethyl methsuximide (active metabolite).

• Excretion: The drug is excreted in the urine, and one percent is excreted as unchanged.

Ingredients

• Active Ingredient: Methsuximide.

• Passive Ingredients: Colloidal silicon dioxide NF, starch, D&C yellow No. 10, sodium lauryl sulfate NF, and FD&C (Federal Food, Drug, and Cosmetic Act) yellow No.6, gelatin NF.

Contraindications for Methsuximide

The drug is not recommended for patients with a history of allergic reactions (hypersensitivity) to Methsuximide or other Succinimides.

What Are the Warnings and Precautions for Methsuximide?

• Blood Dyscrasias: Succinamide is known to cause various fatal outcomes, such as blood dyscrasias (which is the imbalance between four fluids in the body, such as bile, blood, phlegm, and lymph). Therefore, the doctor must advise the patient for periodic blood counts while prescribing Methsuximide, especially if signs of infection, such as fever or sore throat, develop. Symptoms of blood dyscrasias include bruising, swollen glands, fever, sore throat, nose bleeds, bleeding gums, purple or red spots on the body, weakness or severe fatigue, and frequent infections.

• Systemic Lupus Erythematosus (SLE): The drug has also been associated with causing SLE; therefore, Methsuximide should be cautiously prescribed to patients, considering the possibility of this condition. Symptoms of SLE include muscle pain, joint pain and swelling, fatigue, skin rash, low-grade fever, and chest pain worsening with breathing.

• Central Nervous System (CNS) Depression: The drug can also impair the mental and physical abilities of a patient, thus causing CNS (central nervous system) depression. Therefore, the doctor must advise them to avoid operating heavy machinery in such cases.

• Suicidal Thoughts: The drug can cause adverse effects, as anti-epileptic drugs are often linked with the risk of increased suicidal behavior or thoughts. Symptoms include worsening depression, panic attacks, insomnia or troubled sleep, anxiety, restlessness, extreme mania (talking), and irritability. Therefore, the doctor must carefully prescribe the drug by regularly monitoring the worsening of suicidal thoughts, depression, or any unusual mood or behavior changes.

• Hepatic (Liver) Impairment: The drug is also known to cause hepatic impairment in animal studies. Therefore, it should be cautiously prescribed to patients with underlying liver diseases, and they must be advised to undergo regular liver function and urine tests while receiving Methsuximide.

• Withdrawal: Doctors are recommended to discontinue the drug slowly, depending on the patient's unusual aggressiveness, depression, and alterations in behavior. The doctor must also explain to the patient that sudden withdrawal of the drug or increasing or decreasing the dose abruptly can cause the absence of seizure symptoms.

• Appropriate Usage: The drug must be cautiously used in combination with other anticonvulsant drugs to treat patients suffering from both petit mal or absence seizures and tonic-clonic seizures (a type of seizure that causes violent muscle contraction and loss of consciousness). If the drug is not given in combination to patients with mixed seizures, they may develop tonic-clonic seizures.

Drug Interactions:

• Alcohol or ethyl.

• Alizapride.

• Azelastine (nasal) alcohol.

• Blonanserin.

• Brexanolone.

• Brimonidine (topical).

• Bromopride.

• Bromperidol.

• Buprenorphine.

• Cannabidiol.

• Cannabis.

• Chlormethiazole.

• Chlorphenesin carbamate.

• CNS depressants.

• Dimethindene (topical).

• Doxylamine.

• Dronabinol.

• Droperidol.

• Esketamine.

• Flunitrazepam.

• Hydroxyzine.

• Kava Kava.

• Lemborexant.

• Lisuride.

• Lofexidine.

• Magnesium sulfate.

• Mefloquine.

• Methotrimeprazine.

• Metoclopramide.

• Metyrosine.

• Mianserin.

• Minocycline (systemic).

• Nabilone.

• Opioid agonists.

• Orlistat.

• Orphenadrine.

• Oxomemazine.

• Oxybate salt products.

• Oxycodone.

• Paraldehyde.

• Perampane.

• Piribedil.

• Pramipexole.

• Ropinirole.

• Rotigotine.

• Rufinamide.

• Suvorexant.

• Tetrahydrocannabinol.

• Tetrahydrocannabinol and Cannabidiol.

• Thalidomide.

• Trimeprazine.

• Zolpidem.

Use in Specific Populations:

• Pregnancy: The drug is linked with epilepsy and elevated birth defects in children born to women taking anticonvulsant drugs during pregnancy. However, there is a lack of adequate data on the drug's teratogenic effects in humans. Therefore, the drug should not be stopped in cases where it is prescribed for major seizures, as it can cause hypoxia, status epilepticus, and life-threatening situations. In case discontinuing the drug does not have any serious outcomes, depending on the frequency and severity of the seizures, Methsuximide should be stopped before or during pregnancy. Additionally, reported cases also show a greater number of pregnant mothers delivering normal babies while on anticonvulsant therapy for seizures.

• Breastfeeding: No data suggests the presence of this drug in human milk. Therefore, one must consult the doctor if they experience any effects on breastfed babies and impact on milk production.

• Pediatric Use: A small drug dosage (150 milligrams) is recommended for administration to this population group.

• Geriatric Use: The drug dosage, safety, and effectiveness have been established in adults or the geriatric population.