Question

A person on treatment with lithium for a mood disorder presents with seizures, increased reflexes, and epileptic fits. The patient also has a history of severe gastroenteritis. On investigation, the serum lithium level was found to be 1.95 mEq/L. This patient is most likely suffering from

• A. Severe dehydration
• B. Lithium toxicity
• C. Epilepsy
• D. Manic episode

Hint:

Lithium level above about 1.5 mEq/L, plus dehydration from gastroenteritis reducing renal clearance, plus seizures and hyperreflexia, means toxicity.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
A patient on lithium develops seizures, brisk reflexes, and fits after an episode of severe gastroenteritis, and the serum lithium level comes back at 1.95 mEq per litre. We need the condition that best explains this combination.

Step 2: Key Concept:
The safe treatment range for lithium is about 0.6 to 1.2 mEq per litre. Levels above roughly 1.5 mEq per litre are considered toxic, and levels above 2.5 mEq per litre are a severe, life threatening emergency. Signs of lithium toxicity include coarse tremor, ataxia, confusion, increased deep tendon reflexes, and seizures. Gastroenteritis causes vomiting and diarrhoea, which leads to dehydration and salt loss, and this reduces the kidney's ability to clear lithium, letting the drug build up in the blood.

Step 3: Detailed Explanation:
Here the serum lithium of 1.95 mEq per litre sits well above the toxic threshold, so the number itself already points to toxicity rather than a therapeutic level.
The gastroenteritis is not a coincidence, it is the trigger: fluid loss shrank the volume the kidneys had to work with and cut down lithium clearance, so the drug that was previously at a safe dose became toxic.
Increased reflexes and seizures are classic neurological signs of lithium toxicity, since lithium is neurotoxic at high concentration and irritates the nervous system once it builds up.
Severe dehydration alone can cause weakness and low blood pressure, but it does not typically cause seizures and hyperreflexia by itself, and it does not explain why the specific measured lithium level is so high; here dehydration is the cause of the toxicity, not the full diagnosis on its own.
Epilepsy is a primary seizure disorder unrelated to a drug level, and nothing in this history points to an independent seizure condition; the seizure here has a clear drug related cause.
A manic episode would show mood and behavior change, not seizures or a raised drug level, so it does not fit the findings described.

Step 4: Final Answer:
A lithium level of 1.95 mEq per litre with seizures and hyperreflexia, in a patient who became dehydrated from gastroenteritis, is lithium toxicity.