A patient with HIV-AIDS being treated with combined antiviral drugs and * immunosuppressive agents, develops an opportunistic infection caused by Pneumocystis caranii. Which of the following drugs most likely be used in the treatment of pulmonary infection caused by P, caranii?

Correct Answer: C

Rationale: The correct answer is C: Trimethoprim/Sulfamethoxazole. This combination is the first-line treatment for Pneumocystis carinii pneumonia in patients with HIV-AIDS due to its efficacy against the organism. Trimethoprim inhibits bacterial folic acid synthesis, while sulfamethoxazole inhibits bacterial dihydrofolic acid formation. These drugs work synergistically to target different steps in the folic acid synthesis pathway of Pneumocystis carinii, leading to its effective eradication. Metronidazole (A) is used for anaerobic bacterial infections, Carbenicillin (B) is a penicillin derivative mainly used for Gram-negative bacteria, and Penicillin G (D) is not effective against Pneumocystis carinii.

Correct Answer: A

Rationale: Step-by-step rationale for why A (Lamivudine) is correct: 1. Lamivudine is a nucleoside analog reverse transcriptase inhibitor used to treat chronic hepatitis B. 2. It inhibits the replication of the hepatitis B virus, reducing viral load and liver damage. 3. Clinical studies have shown its efficacy in improving liver function and reducing the risk of cirrhosis. 4. Lamivudine is recommended as a first-line treatment option by major medical guidelines. Summary of why other choices are incorrect: B. Human interferon α: While interferon therapy was previously used, it is no longer recommended as a first-line treatment due to its side effects and lower efficacy compared to newer drugs. C. Amantadine: Amantadine is not recommended for the treatment of chronic hepatitis B as it is not effective against the hepatitis B virus. D. (: This is not a valid drug option for treating chronic hepatitis B.

Correct Answer: B

Rationale: The correct answer is B: Primaquine. Primaquine is a radical curative drug for Plasmodium vivax malaria, as it targets the hypnozoite stage in the liver, preventing relapses. It is also used as prophylaxis in Chloroquine-sensitive regions due to its efficacy against P. vivax and P. ovale. Rationale: 1. Quinine (A) is not a radical curative drug for P. vivax malaria. It is mainly used for treatment of acute malaria. 2. Meoquine (C) is not a radical curative drug for P. vivax malaria and is used more for prophylaxis in certain regions. 3. Chloroquine (D) is not a radical curative drug for P. vivax malaria and is primarily used for treatment and prevention of malaria caused by susceptible strains of Plasmodium species.

Correct Answer: D

Rationale: Step 1: Piperacillin is a semisynthetic penicillin with extended spectrum against gram-negative bacilli. Step 2: It is acid-resistant, meaning it can withstand acidic environments in the stomach. Step 3: However, it is not penicillinase-resistant, making it susceptible to penicillinase enzymes. Step 4: Cloxacillin (A) and Amoxicillin (B) are penicillinase-resistant but do not have extended gram-negative activity. Step 5: Phenoxymethyl penicillin (C) is neither acid-resistant nor penicillinase-resistant. In summary, Piperacillin is the correct choice due to its extended spectrum against gram-negative bacilli and acid resistance, despite not being penicillinase-resistant.

Correct Answer: C

Rationale: The correct answer is C: Hydrochlorothiazide. Hydrochlorothiazide is a thiazide diuretic that can lead to hyperuricemia, a risk factor for gout. Thiazide diuretics decrease the excretion of uric acid, leading to its accumulation and potential for gout attacks. Furosemide (A) is a loop diuretic that does not have a significant impact on uric acid levels. Spironolactone (B) and Triamterene (D) are potassium-sparing diuretics and do not directly affect uric acid levels. So, Hydrochlorothiazide is the most likely diuretic causing the gout attack in this case.