Which drug decreases the threshold of seizures?

NORCET 1 - 2020

Pharmacology

Easy

Appeared in: NORCET 1 - 2020

Explanation

Lithium is a mood stabilizer primarily used for bipolar disorder.
A significant adverse effect of lithium, especially at toxic levels (greater than 1.5 mEq/L), is the lowering of the seizure threshold.
By lowering the threshold, lithium makes the brain's neurons more susceptible to the abnormal, excessive electrical activity that characterizes a seizure.
This effect is opposite to that of anticonvulsant medications.

Option B: This is incorrect. Anticonvulsants are a class of drugs specifically designed to treat and prevent seizures by increasing the seizure threshold, making neurons less excitable.
Option C: This is incorrect. Benzodiazepines raise the seizure threshold by enhancing the activity of GABA, the brain's primary inhibitory neurotransmitter. They are used to stop ongoing seizures.
Option D: This is incorrect. Barbiturates, like benzodiazepines, increase the seizure threshold by potentiating GABAergic inhibition, thereby suppressing seizure activity.

Visual 1: Diagram: Seizure Threshold Balance. A visual scale showing the balance between excitatory (e.g., glutamate) and inhibitory (e.g., GABA) neurotransmission. The diagram can illustrate how Lithium tips the scale towards excitation (lowering the threshold), while anticonvulsants, benzodiazepines, and barbiturates tip it towards inhibition (raising the threshold).

Clinical Relevance

Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Pharmacology: Drug Effects on Seizure Threshold in acute care settings.
Nurses must meticulously monitor serum lithium levels due to the narrow therapeutic window (0.6-1.2 mEq/L). Toxicity can occur at levels close to the therapeutic range, increasing seizure risk.
Patient education is a critical nursing responsibility. Patients on lithium must be taught to maintain consistent fluid and salt intake, recognize early signs of toxicity (e.g., tremor, nausea, confusion), and understand the importance of regular blood tests.
What if? A patient on lithium reports having the flu with vomiting and diarrhea for two days. The nurse should recognize this as a high-risk situation for dehydration, which can lead to lithium toxicity. The priority is to advise the patient to hold the lithium dose and seek immediate medical evaluation, likely including a stat serum lithium level.

How to Approach the Question

First, understand the key term 'decreases the threshold of seizures'. This means a drug that makes seizures more likely to happen.
Next, evaluate each option based on its primary therapeutic purpose.
Recognize that 'Anticonvulsants', 'Benzodiazepine', and 'Barbiturate' are all categories of drugs used to prevent or stop seizures. Their mechanism must involve increasing the seizure threshold.
By elimination, Lithium is the only option that does not fit the profile of an anti-seizure medication.
Recall or deduce that Lithium, a mood stabilizer, has a known adverse effect of lowering the seizure threshold, especially in toxicity. This confirms it as the correct answer.

Concept Tested & Keywords

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