Anticonvulsant Medications Overview

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Questions and Answers

What are the major symptoms of withdrawal from certain medications?

Headache, nausea, and fatigue

Seizures, delirium, and hypothermia (correct)

Increased appetite and weight gain

Depression, anxiety, and insomnia

Which of the following can develop tolerance due to hepatic microsomal enzyme induction?

Succinimides

Benzodiazepines

Oxazolidinediones

Barbiturates (correct)

What is the lethality ratio of barbiturates to their hypnotic dose?

About 5 times

About 20 times

About 10 times (correct)

About 15 times

How many substituents are required at the 5-position for barbiturates?

Two substituents Signup and view all the answers

Which medication class is noted for having significant withdrawal symptoms that may last up to two weeks?

Oxazolidinediones Signup and view all the answers

What is a common effect of barbiturate overdose?

Respiratory depression and lethality Signup and view all the answers

Which of the following symptoms is NOT associated with withdrawal from certain medications?

Hypertension Signup and view all the answers

What duration is tolerance to barbiturates expected to develop?

2 weeks Signup and view all the answers

In which scenario would therapeutic drug monitoring be particularly beneficial?

When there is suspected medication adherence issues Signup and view all the answers

What is a critical factor to consider when cross-titrating anticonvulsant medications?

Whether the new medication belongs to the same drug class as the old one Signup and view all the answers

Which consideration might lead to a higher risk of side effects when switching medications?

Utilizing a formulation or generic substitution Signup and view all the answers

What should ideally happen before tapering off an old anticonvulsant medication?

The goal dose of the new medication should be reached Signup and view all the answers

What principle should guide treatment decisions in medication management?

Always treat the patient rather than fixate on specific numbers Signup and view all the answers

How many carbon atoms are optimal in the two substituents at position 5?

5 - 7 carbon atoms Signup and view all the answers

What effect does having a phenyl group as one of the 5-substituents have?

Increases the duration of action Signup and view all the answers

What is the result of replacing the 2-oxo group with a 2-thio group?

Significant loss in duration of action Signup and view all the answers

What type of duration is associated with the compound after the 2-oxo group is replaced with a 2-thio group?

Ultra-short duration of action Signup and view all the answers

Which of the following is NOT mentioned as an optimal substituent at position 5?

Hydroxyl group Signup and view all the answers

What is the chemical significance of having optimal carbon atoms in the substituents at position 5?

It optimizes duration of action Signup and view all the answers

What structural change is indicated to significantly impact drug action duration?

Replacement of oxygen with sulfur Signup and view all the answers

Which group at position 5 is indicated to have a specific impact on the action duration?

Phenyl group Signup and view all the answers

What is the primary use of Fosphenytoin?

Status epilepticus and seizures during neurosurgery Signup and view all the answers

What is a significant characteristic of Carbamazepine's metabolism?

It leads to the formation of a toxic epoxide. Signup and view all the answers

Which of the following statements about Carbamazepine is true?

It induces various enzymes including 3A4 and 2C19. Signup and view all the answers

Which cytochrome P450 enzyme does Carbamazepine primarily induce?

CYP3A4 Signup and view all the answers

What type of drug is Fosphenytoin characterized as?

A prodrug of Phenytoin Signup and view all the answers

Which of the following is a reason for the past widespread use of barbiturates?

Their effectiveness in inducing sleep Signup and view all the answers

The metabolite epoxide generated from Carbamazepine is known to be:

More toxic than Carbamazepine Signup and view all the answers

Which of the following describes Fosphenytoin’s administration route?

Intravenous only Signup and view all the answers

Why is Carbamazepine considered an autoinducer?

It induces its own metabolism leading to decreased levels. Signup and view all the answers

What type of activity does the epoxide of Carbamazepine exhibit?

Toxic Signup and view all the answers

Which patient populations are indicated to have a consideration for HLA-A*3101 testing?

Japanese and Native American Signup and view all the answers

What is advised for patients with a high initial dose of Lamotrigine?

Consider co-administration with valproic acid Signup and view all the answers

What is a potential consideration when introducing a second ASM in treatment?

Monitor for increased metabolic interactions Signup and view all the answers

Which medications may require careful monitoring when used in combination with Lamotrigine?

Valproic acid and Phenytoin Signup and view all the answers

What might be a consequence of rapid dose increases of ASM?

Increased risk of adverse effects Signup and view all the answers

In the management of epilepsy, which of the following is true regarding dosage adjustments?

Patients may require a dose reduction of the first ASM when starting a second ASM Signup and view all the answers

Which of these is a correct statement about the medication Phenytoin?

Phenytoin may increase metabolism of Lamotrigine Signup and view all the answers

Which populations mentioned are associated with higher sensitivity to HLA-A*3101?

Japanese and Southern Indian Signup and view all the answers

Study Notes

Fosphenytoin

Fosphenytoin is the prodrug of phenytoin.
This anticonvulsant is designed for intravenous administration.
It is used for status epilepticus and seizures occurring during neurosurgery.

Carbamazepine and Oxcarbazepine

These drugs are useful for various types of seizures.
Carbamazepine induces various enzymes including 3A4, 1A2, 2B6, 2C19, 2C8, and 2C9.
It is considered an autoinducer, which means it also induces uridine 5´-diphospho-glucuronosyltransferases (UGTs).
Carbamazepine’s epoxide is more toxic than carbamazepine.

Barbiturates

Barbiturates are anticonvulsants that were widely used drugs for inducing sleep in 1958.
Withdrawal symptoms, such as seizures, delirium, and hypothermia, can persist for up to 2 weeks after discontinuation of the drug.
Tolerance to barbiturates develops within 2 weeks of treatment due to the induction of hepatic microsomal enzymes.
The lethal dose of barbiturates is approximately 10 times the hypnotic dose.
Barbiturates require two substituents at the 5-position of the molecule.
Optimal total number of carbon atoms in the two 5-substituents is 5-7.
A phenyl group at the 5-position increases the duration of action.
Replacing the 2-oxo group with a 2-thio group (change in oxygen to sulfur) results in a significantly shorter duration of action.

Therapeutic Drug Monitoring (TDM)

TDM can be useful in cases of suspected toxicity, suspected drug interactions, pregnancy, critical illness, and if the patient is taking phenytoin.
TDM may be used in formulation or generic substitution.
It is important not to over-rely on numbers and rather focus on the needs of the patient.

Strategies for Cross-titrating Anti-Seizure Medications (ASMs)

The strategy for cross-titrating ASMs depends on multiple factors.
Determine the reason for switching medications.
Consider the patient's sensitivity to medication changes and adherence to the prescribed regimen.
Assess if the new medication belongs to the same drug class as the old medication.
The goal is to reach the desired dose of the new ASM before tapering the old medication.
Fast tapering of ASMs increases risk of breakthrough seizures.
It is essential to monitor the patient for side effects, especially if the new medication is in a different class.
Patients with HLA-A*3101 are more likely to experience Stevens-Johnson syndrome when taking lamotrigine.
Higher initial doses of lamotrigine, rapid dose increases, and co-administration with valproic acid increase the risk of Stevens-Johnson syndrome.

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Description

This quiz covers key anticonvulsant medications including Fosphenytoin, Carbamazepine, and Barbiturates. Learn about their uses, mechanisms, and potential side effects. Test your knowledge on these important drugs in the management of seizures.