Clinical Pharmacology and Drug Toxicity Practice Questions

Q: A 34-year-old rickshaw puller who has been using heroin for the past 10 years was found unconscious by his family members and brought to the casualty. On examination, he exhibited bradycardia, shallow breathing, constricted pupils, a blood pressure of 100/70 mmHg, brisk bilateral deep tendon reflexes, and flexor plantar reflexes on both sides. Which is the best treatment for him?

Naloxone. ***Naloxone*** - The patient presents with classic signs of **opioid overdose**: unconsciousness, bradycardia, shallow breathing, and constricted pupils. **Naloxone** is a potent opioid antagonist that rapidly reverses these effects. - Its rapid onset of action and ability to displace opioids from receptors makes it the **gold standard** emergency treatment for opioid overdose. *Buprenorphine* - This is a **partial opioid agonist** used for **opioid dependence treatment**, not for acute overdose reversal. - While it can partially antagonize other opioids, its primary role is in addiction management, not rapid resuscitation. *Flumazenil* - **Flumazenil** is an antagonist used to reverse the effects of **benzodiazepines**, not opioids. - Administering flumazenil in an opioid overdose would be ineffective and potentially dangerous if co-ingestion of benzodiazepines is suspected but not predominant. *Methadone* - **Methadone** is a **long-acting opioid agonist** used for **opioid dependence treatment** and chronic pain management. - Administering methadone to an acutely overdosed patient would worsen their condition by adding more opioid effect.

Q: Which of the following treatments is not indicated in digitalis poisoning?

Hemodialysis. ***Hemodialysis*** - **Digitoxin** and **digoxin** have large volumes of distribution and are extensively protein-bound, making them poorly dialyzable. - Therefore, **hemodialysis** is generally not effective in removing these cardiac glycosides from the body in cases of poisoning. *Potassium* - **Hypokalemia** can exacerbate digitalis toxicity by increasing digitalis binding to the Na+/K+ ATPase, thus potassium supplementation is indicated. - However, in cases of **hyperkalemia** due to severe poisoning, potassium administration would be contraindicated. *Phenytoin* - **Phenytoin** is an antiarrhythmic drug that can be used to treat **digitalis-induced tachyarrhythmias**, particularly ventricular arrhythmias. - It works by **suppressing ventricular ectopy** and improving AV nodal conduction. *Lidocaine* - **Lidocaine** is a Class IB antiarrhythmic that is effective in treating **ventricular arrhythmias** caused by digitalis toxicity. - It acts by **blocking sodium channels** and reducing automaticity in the ventricles, thereby stabilizing the cardiac membrane.

Q: In all of the following conditions, prostanoids may be used, except:

Closure of PDA. ***Closure of PDA*** - Prostanoids, specifically **prostaglandin E1 (PGE1)**, are used to **maintain patency** of the ductus arteriosus, not to close it. [1], [3] - **Inhibitors of prostaglandin synthesis**, such as indomethacin, are used to promote the closure of a patent ductus arteriosus (PDA). *Glaucoma* - **Prostaglandin F2̱ (PGF2̱) analogs** like latanoprost are a first-line treatment for **open-angle glaucoma**. [1], [2] - They work by **increasing uveoscleral outflow** of aqueous humor, thereby reducing intraocular pressure. [1] *Gastric ulcer* - The **synthetic prostaglandin E1 (PGE1) analog misoprostol** is used to prevent and treat **NSAID-induced gastric ulcers**. [1], [2] - It works by **inhibiting acid secretion**, enhancing mucosal blood flow, and increasing mucus and bicarbonate production. [1] *Platelet coagulation disorders* - **Prostacyclin (PGI2)**, a type of prostanoid, is a potent **vasodilator** and **inhibitor of platelet aggregation**. [1] - Analogs of prostacyclin, such as epoprostenol, are used in conditions like **pulmonary hypertension** and to **prevent clotting** in extracorporeal circulation (e.g., dialysis). [1]

Q: What is the treatment for Dabigatran toxicity?

Idarucizumab. ***Idarucizumab*** - **Idarucizumab** is a specific humanized monoclonal antibody fragment (Fab) that directly binds to dabigatran and its metabolites, effectively **reversing its anticoagulant effects**. - It is indicated for patients requiring urgent reversal of dabigatran's anticoagulant effects due to life-threatening or uncontrolled bleeding, or for emergency surgery/urgent procedures. *Protamine sulphate* - **Protamine sulphate** is used to reverse the anticoagulant effects of **heparin** and low molecular weight heparins, but it is ineffective against direct oral anticoagulants like dabigatran. - Its mechanism involves forming a stable ion pair with heparin, neutralizing its activity. *Andexanet alfa* - **Andexanet alfa** is a recombinant modified human factor Xa (FXa) decoy protein used to reverse the anticoagulant activity of **FXa inhibitors** (e.g., rivaroxaban, apixaban). - It does not bind to or reverse the effects of direct thrombin inhibitors like dabigatran. *Argatroban* - **Argatroban** is a **direct thrombin inhibitor** (similar mechanism of action to dabigatran) and is used as an anticoagulant, particularly in patients with heparin-induced thrombocytopenia. - It would worsen dabigatran toxicity rather than treat it, as both drugs inhibit thrombin.

Q: Which of the following is a serious adverse effect of prolonged sodium nitroprusside infusion due to cyanide toxicity?

Lactic acidosis. ***Lactic acidosis*** - This is the correct answer as **lactic acidosis** is a serious adverse effect of sodium nitroprusside due to **cyanide toxicity**. - Sodium nitroprusside is metabolized to **cyanide**, which inhibits **cytochrome oxidase** in the mitochondrial electron transport chain, leading to **impaired aerobic metabolism** and accumulation of **lactate**. - This is particularly concerning with **prolonged infusions** (>24-48 hours) or in patients with **renal or hepatic dysfunction**. - Clinical monitoring includes **serum lactate levels** and **metabolic acidosis** on arterial blood gas. *Hypotension* - While **hypotension** is the primary pharmacological effect and most common adverse effect of sodium nitroprusside, it is **dose-dependent** and **reversible** with rate adjustment. - It is not specifically related to **cyanide toxicity** from prolonged use, which is what makes nitroprusside particularly dangerous. - Managed by **titrating infusion rate** and continuous **blood pressure monitoring**. *Headache* - **Headache** is a common side effect due to **cerebral vasodilation**, but it is generally **mild** and not considered a serious adverse effect. - Not related to the **cyanide toxicity** mechanism that makes prolonged sodium nitroprusside use hazardous. *Lactic acidosis, psychosis, and headache* - While this combination represents multiple effects that can occur with sodium nitroprusside, it is unnecessarily comprehensive for a single-best-answer question. - **Psychosis** can occur with severe cyanide toxicity but is less commonly emphasized than **lactic acidosis** as the key marker of toxicity. - The most clinically relevant single answer focusing on **cyanide toxicity** is **lactic acidosis**.

Q: Which of the following is used as an antidote for organophosphorus poisoning?

Pralidoxime aldoxime methiodide (PAM). ***Pralidoxime aldoxime methiodide (PAM)*** - **Pralidoxime (PAM)** is an **oxime reactivator** that works by regenerating the inhibited **acetylcholinesterase** enzyme, thereby reversing the effects of organophosphorus poisoning. - It is particularly effective in treating the **nicotinic symptoms** (e.g., muscle weakness, paralysis) of severe organophosphate poisoning. *N-acetyl cysteine* - **N-acetyl cysteine (NAC)** is the antidote for **acetaminophen (paracetamol) overdose**, not organophosphorus poisoning. - It works by replenishing **glutathione** stores, which are crucial for detoxifying acetaminophen metabolites. *Physostigmine* - **Physostigmine** is an **acetylcholinesterase inhibitor** that increases acetylcholine levels. - It is used to reverse the effects of **anticholinergic poisoning**, not organophosphorus poisoning, which overstimulates the cholinergic system. *Flumazenil* - **Flumazenil** is a **benzodiazepine receptor antagonist** used to reverse the sedative effects of **benzodiazepine overdose**. - It does not have any role in the treatment of organophosphorus poisoning.

Q: What is the maximum dose of plain lignocaine (in mg) for adults?

300. ***300 mg*** - The maximum recommended dose of **plain lidocaine** (without epinephrine) for adults is typically **300 mg** or 4.5 mg/kg, whichever is less. - Exceeding this dose can increase the risk of **systemic toxicity**, including central nervous system and cardiovascular effects. *500 mg* - This dose is generally considered the maximum for **lidocaine with epinephrine** in adults, as **epinephrine** causes vasoconstriction and delays systemic absorption of lidocaine. - For **plain lidocaine**, 500 mg would be an overdose and significantly increase the risk of toxicity. *700 mg* - This is well above the recommended maximum dose for both plain lidocaine and lidocaine with epinephrine, posing a **severe risk of toxicity**. - Such a high dose could lead to **seizures**, cardiac arrhythmias, and even **cardiac arrest**. *1000 mg* - This dose is extremely dangerous and far exceeds any recommended maximum for lidocaine, regardless of whether it contains epinephrine. - Administration of 1000 mg of lidocaine would almost certainly result in **severe and potentially fatal toxicity**.

Question 1

A 34-year-old rickshaw puller who has been using heroin for the past 10 years was found unconscious by his family members and brought to the casualty. On examination, he exhibited bradycardia, shallow breathing, constricted pupils, a blood pressure of 100/70 mmHg, brisk bilateral deep tendon reflexes, and flexor plantar reflexes on both sides. Which is the best treatment for him?

Accepted Answer

Naloxone

Answer

Buprenorphine

Answer

Flumazenil

Answer

Methadone

Question 2

Which of the following treatments is not indicated in digitalis poisoning?

Accepted Answer

Hemodialysis

Answer

Potassium

Answer

Phenytoin

Answer

Lidocaine

Question 3

In all of the following conditions, prostanoids may be used, except:

Accepted Answer

Closure of PDA

Answer

Glaucoma

Answer

Gastric ulcer

Answer

Platelet coagulation disorders

Question 4

The characteristic finding in chloroquine retinopathy is

Accepted Answer

Bull's eye maculopathy

Answer

Retinopathy that resolves immediately after stopping the drug

Answer

Primarily CNS involvement rather than retinal

Answer

Vision loss that is usually reversible

Question 5

What is the treatment for Dabigatran toxicity?

Accepted Answer

Idarucizumab

Answer

Protamine sulphate

Answer

Andexanet alfa

Answer

Argatroban

Question 6

Which of the following statements about phase IV clinical trials is correct?

Accepted Answer

It involves monitoring the long-term effects and safety of drugs.

Answer

It is primarily focused on the efficacy of the drug.

Answer

It is conducted before a drug is submitted for approval.

Answer

It focuses primarily on determining the optimal dosage for patients.

Question 7

Which antidiabetic medication is safe in both liver and renal failure?

Accepted Answer

Linagliptin

Answer

None of the options

Answer

Insulin

Answer

Both

Question 8

Which of the following is a serious adverse effect of prolonged sodium nitroprusside infusion due to cyanide toxicity?

Accepted Answer

Lactic acidosis

Answer

Hypotension

Answer

Headache

Answer

Lactic acidosis, psychosis, and headache

Question 9

Which of the following is used as an antidote for organophosphorus poisoning?

Accepted Answer

Pralidoxime aldoxime methiodide (PAM)

Answer

N-acetyl cysteine

Answer

Physostigmine

Answer

Flumazenil

Question 10

What is the maximum dose of plain lignocaine (in mg) for adults?

Accepted Answer

300

Answer

500

Answer

700

Answer

1000

Clinical Pharmacology and Drug Toxicity — MCQs

Clinical Pharmacology and Drug Toxicity — MCQs

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