Which of the following groups of antibiotics demonstrates a bactericidal effect?

Correct Answer: C

Rationale: The correct answer is C: Penicillins. Penicillins demonstrate bactericidal effects by interfering with bacterial cell wall synthesis, leading to cell lysis and death. Tetracyclines and macrolides are bacteriostatic, inhibiting bacterial growth but not directly killing them. Choice D is incorrect as not all antibiotics listed exhibit bactericidal effects.

Correct Answer: B

Rationale: The correct answer is B: Metronidazole. Metronidazole is the drug of choice for extraluminal amebiasis due to its high efficacy against Entamoeba histolytica. It is a nitroimidazole antibiotic that works by disrupting the DNA structure of the parasite. Other choices are incorrect because: A: Iodoquinol is mainly used for luminal amebiasis. C: Diloxanide is also used for luminal amebiasis. D: Tetracycline is not the first-line treatment for extraluminal amebiasis.

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: B

Rationale: The correct answer is B: Sotalol. Sotalol is a non-selective beta-blocker and a class III antiarrhythmic agent that blocks both beta receptors and potassium (K+) channels. By blocking beta receptors, it decreases heart rate and contractility. Blocking K+ channels prolongs the action potential duration, aiding in the treatment of various arrhythmias. Quinidine (A) is a class I antiarrhythmic that primarily blocks Na+ channels. Propranolol (C) is a selective beta-blocker that does not affect K+ channels. Digoxin (D) is a cardiac glycoside that inhibits the sodium-potassium pump but does not block beta receptors or K+ channels.

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.