Action mechanism of methotrexate is:

Correct Answer: A

Rationale: The correct answer is A: Inhibition of dihydrofolate reductase. Methotrexate inhibits dihydrofolate reductase, an enzyme involved in the synthesis of nucleotides. This leads to decreased production of DNA, RNA, and proteins, inhibiting cell proliferation. Choices B and C are incorrect as methotrexate does not activate cell differentiation or deplete serum asparagine. D is incorrect as methotrexate's mechanism of action is specifically through inhibiting dihydrofolate reductase, not all of the above.

Correct Answer: C

Rationale: The correct answer is C: Amiodarone. This drug is an antiarrhythmic medication commonly associated with side effects such as palpitations, insomnia, diarrhea, and increased sweating. Quinidine (A) and Lidocaine (B) are also antiarrhythmic drugs but are less likely to cause the specific symptoms described. Adenosine (D) is a drug used for treating certain types of irregular heartbeats but does not typically cause the combination of symptoms mentioned. Therefore, based on the patient's symptoms, Amiodarone is the most likely drug taken.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.