Which of the following is the drug of choice for preoperative antibiotic prophylaxis in a patient undergoing cardiac surgery?
A chronic smoker was on nicotine replacement therapy and clonidine tablets for smoking de-addiction. He stopped taking clonidine tablets and now presents with a headache. What is the reason behind this condition?
A female patient presents to the emergency department with severe restlessness, palpitations, and tremors. She is a known case of bronchial asthma. On examination, the neck looks swollen. Blood pressure is elevated, and tachycardia is noted. ECG shows atrial fibrillation. Which of the following drugs is used for immediate management in this patient?
A patient comes to the casualty with organophosphate poisoning. He was started on atropine infusion and pralidoxime. After 2 hours, the patient had a sudden rise in temperature. What is the most likely cause of the fever?
Which of the following is NOT a side effect of amiodarone?
NEET-PG 2023 - Pharmacology NEET-PG Practice Questions and MCQs
Question 11: Which of the following is the drug of choice for preoperative antibiotic prophylaxis in a patient undergoing cardiac surgery?
- A. Cefazolin (Correct Answer)
- B. Penicillin
- C. Clindamycin
- D. Vancomycin
Explanation: ***Cefazolin*** - **Cefazolin** is a first-generation cephalosporin that provides excellent coverage against **Staphylococcus aureus** and **Streptococcus species**, which are common pathogens in surgical site infections in cardiac surgery. - It has a favorable safety profile, long half-life allowing for convenient dosing, and good tissue penetration, making it the preferred choice for **preoperative antibiotic prophylaxis** in most cardiac surgery cases. *Penicillin* - **Penicillin** has a narrow spectrum of activity compared to cefazolin and does not adequately cover all potential pathogens in cardiac surgery, particularly **methicillin-susceptible Staphylococcus aureus (MSSA)**. - Due to its limited spectrum, penicillin is generally not recommended for routine **surgical prophylaxis**, especially in complex procedures like cardiac surgery. *Clindamycin* - **Clindamycin** is an alternative for patients with **beta-lactam allergies**, providing coverage against gram-positive organisms and anaerobes. - However, for routine prophylaxis without a specific allergy or high risk of resistant organisms, **clindamycin** is less effective than cefazolin against the most prevalent surgical pathogens. *Vancomycin* - **Vancomycin** is reserved for patients with a known **penicillin allergy** or a high risk of **methicillin-resistant Staphylococcus aureus (MRSA)** colonization or infection. - Its routine use as a primary prophylactic agent in cardiac surgery is discouraged to prevent the development of **vancomycin resistance**.
Question 12: A chronic smoker was on nicotine replacement therapy and clonidine tablets for smoking de-addiction. He stopped taking clonidine tablets and now presents with a headache. What is the reason behind this condition?
- A. Postural hypotension
- B. Receptor upregulation
- C. Rebound hypertension (Correct Answer)
- D. Receptor hypersensitivity
Explanation: ***Rebound hypertension*** - **Clonidine withdrawal** can cause a sudden surge in blood pressure due to increased sympathetic activity, leading to **rebound hypertension** and symptoms like headaches. - This occurs because chronic clonidine use suppresses sympathetic outflow, and its abrupt discontinuation unmasks this suppressed activity, causing a hypertensive crisis. *Postural hypotension* - **Postural hypotension** is a common side effect of clonidine due to its vasodilatory effects, causing blood pressure to drop when standing. - However, the patient's headache following clonidine cessation is more indicative of a **hypertensive event**, not hypotension. *Receptor upregulation* - **Receptor upregulation** refers to an increase in the number of receptors, often in response to prolonged antagonism or decreased ligand exposure. - While receptor changes occur, the primary mechanism of clonidine withdrawal is the **overcompensation** of the sympathetic nervous system, not simply an increased number of receptors. *Receptor hypersensitivity* - **Receptor hypersensitivity** implies an exaggerated response to a normal concentration of a neurotransmitter, which can contribute to withdrawal symptoms. - While it plays a role, the more immediate and critical cause of the headache is the rapid increase in blood pressure due to **rebound sympathetic activity**.
Question 13: A female patient presents to the emergency department with severe restlessness, palpitations, and tremors. She is a known case of bronchial asthma. On examination, the neck looks swollen. Blood pressure is elevated, and tachycardia is noted. ECG shows atrial fibrillation. Which of the following drugs is used for immediate management in this patient?
- A. Esmolol (Correct Answer)
- B. Diltiazem
- C. Propranolol
- D. Propylthiouracil
Explanation: ***Esmolol*** - The patient presents with **thyroid storm** (severe restlessness, palpitations, tremors, swollen neck, elevated BP, tachycardia, atrial fibrillation), which is a **life-threatening endocrine emergency** requiring immediate intervention. - **Beta-blockers are first-line therapy** for thyroid storm as they: (1) control cardiovascular manifestations, (2) block peripheral effects of thyroid hormones, and (3) inhibit peripheral conversion of T4 to T3. - **Esmolol** is the **optimal choice** in this asthmatic patient because it is a **cardioselective β1-blocker** with an **ultra-short half-life (9 minutes)**, allowing rapid titration and immediate discontinuation if bronchospasm occurs. - Its cardioselectivity minimizes (though does not eliminate) the risk of bronchospasm, and close monitoring makes it safer than avoiding beta-blockade entirely in this life-threatening condition. *Propranolol* - **Propranolol** is highly effective in thyroid storm and is traditionally considered first-line therapy. - However, it is a **non-selective beta-blocker** that blocks both β1 (cardiac) and β2 (bronchial) receptors, making it **relatively contraindicated in asthma** due to significant risk of severe bronchospasm. - In this patient with known asthma, esmolol is preferred over propranolol. *Diltiazem* - **Diltiazem** is a **calcium channel blocker** useful for rate control in atrial fibrillation and is safe in asthmatic patients. - However, in **thyroid storm**, it does NOT address the underlying pathophysiology: it does not block peripheral thyroid hormone effects or inhibit T4 to T3 conversion. - While it may control heart rate, **beta-blockade is essential** for managing the acute thyroid storm crisis, making diltiazem inadequate as monotherapy for immediate management. *Propylthiouracil* - **Propylthiouracil (PTU)** is an **antithyroid drug** that inhibits thyroid hormone synthesis and blocks peripheral conversion of T4 to T3. - While PTU is crucial in treating the **underlying hyperthyroidism** in thyroid storm, it has a **delayed onset of action** (hours to days) and does not provide immediate relief of acute cardiovascular manifestations. - It must be combined with beta-blockers for comprehensive thyroid storm management.
Question 14: A patient comes to the casualty with organophosphate poisoning. He was started on atropine infusion and pralidoxime. After 2 hours, the patient had a sudden rise in temperature. What is the most likely cause of the fever?
- A. Side effect of pralidoxime.
- B. Result of organophosphate poisoning.
- C. Unrelated or unknown cause.
- D. Fever due to atropine toxicity. (Correct Answer)
Explanation: ***Fever due to atropine toxicity.*** - **Atropine** blocks muscarinic receptors, leading to inhibition of **sweat glands** and subsequent rise in body temperature (hyperthermia), especially with high doses or prolonged infusion. - Given the patient is receiving an **atropine infusion** and developed fever, **atropine toxicity** is a primary concern. *Side effect of pralidoxime.* - While pralidoxime can cause side effects like dizziness, blurred vision, or tachycardia, **fever is not a typical side effect** of pralidoxime. - Pralidoxime works by **regenerating acetylcholinesterase** [2, 3] and does not directly interfere with thermoregulation in a way that would cause fever. *Result of organophosphate poisoning.* - **Organophosphate poisoning** typically causes **hypothermia** due to excessive cholinergic stimulation leading to peripheral vasodilation and increased sweating [1]. - **Fever** is not a direct result of the acute phase of organophosphate poisoning itself, but rather a complication of treatment or other factors. *Unrelated or unknown cause.* - While possible, it's less likely to be "unrelated or unknown" when a clear pharmacological explanation (**atropine toxicity**) exists for fever in the context of the patient's treatment. - It would be important to first rule out known causes related to the ongoing treatment before attributing it to an unknown cause.
Question 15: Which of the following is NOT a side effect of amiodarone?
- A. Corneal microdeposits
- B. Photosensitivity
- C. Tachycardia (Correct Answer)
- D. Pulmonary fibrosis
Explanation: ***Tachycardia*** - **Amiodarone** is an antiarrhythmic drug primarily used to treat and prevent **tachyarrhythmias**, meaning it generally slows down heart rate and is not associated with causing tachycardia. - Its main effect is to prolong the **refractory period** in myocardial cells, which helps to stabilize abnormal heart rhythms, rather than inducing them. *Pulmonary fibrosis* - **Amiodarone** is well-known for its potential to cause **pulmonary toxicity**, including **interstitial lung disease** and **pulmonary fibrosis**, which can be severe and even fatal. - This side effect is thought to be dose-dependent and can manifest as shortness of breath and cough, requiring careful monitoring. *Corneal microdeposits* - **Corneal microdeposits**, often described as **whorl keratopathy** or **cornea verticillata**, are a very common and usually benign side effect of **amiodarone**. - These deposits typically do not affect vision but can cause blurred vision or halos around lights in some patients. *Photosensitivity* - **Photosensitivity** is a common dermatological side effect of **amiodarone**, leading to an exaggerated sunburn reaction or a grayish-blue skin discoloration in sun-exposed areas. - Patients are advised to use **sunscreen** and protective clothing while on **amiodarone** to minimize this risk.