Which of the following statements about lamotrigine is correct?
Which is a GABA transaminase inhibitor?
Most clinically significant side effect of topiramate requiring immediate medical attention?
What serious side effect may lead to the discontinuation of felbamate?
Which of the following is NOT typically produced by local anesthetics?
Which of the following is a benzylisoquinoline muscle relaxant?
Which medication increases insulin secretion from beta cells?
Which of the following antidiabetic drugs (other than insulin) is indicated as adjunct therapy for the management of both type I and type II diabetes mellitus?
Which of the following statements about sitagliptin is false?
What is a potential risk associated with the use of thiazolidinediones in the treatment of type 2 diabetes?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 81: Which of the following statements about lamotrigine is correct?
- A. Is the first choice for absence seizures.
- B. Has a half-life of approximately 24 hours. (Correct Answer)
- C. Is not significantly metabolized in the liver.
- D. Has decreased efficacy in treating depressive episodes.
Explanation: ***Has a half-life of approximately 24 hours.*** - Lamotrigine's **half-life** is typically around **24 to 33 hours** in adults, which allows for once or twice-daily dosing. - This relatively long half-life is advantageous for maintaining **stable plasma concentrations** and improving patient adherence. *Is the first choice for absence seizures.* - **Ethosuximide** or **valproate** are generally considered first-line treatments for **absence seizures**. - Lamotrigine is not the preferred initial therapy due to its **slower titration** and occasional lack of efficacy in this seizure type. *Is not significantly metabolized in the liver.* - Lamotrigine is **significantly metabolized** in the liver, primarily through **glucuronidation** by the **UGT1A4 enzyme**. - This hepatic metabolism explains many of its **drug interactions**, particularly with other antiepileptic drugs affecting UGT enzymes. *Has decreased efficacy in treating depressive episodes.* - Lamotrigine is known for its **mood-stabilizing properties** and is effective in treating and preventing **depressive episodes**, particularly in **bipolar disorder**. - Its efficacy in depression is a key distinguishing feature, making it a valuable option for patients with comorbid mood disorders.
Question 82: Which is a GABA transaminase inhibitor?
- A. TCA
- B. Valproate (Correct Answer)
- C. Gabapentin
- D. Sertraline
Explanation: ***Valproate*** - Valproate is known to inhibit **GABA transaminase**, an enzyme responsible for the breakdown of **gamma-aminobutyric acid (GABA)**. - By inhibiting this enzyme, valproate increases the concentration of **GABA** in the brain, enhancing its inhibitory effects and contributing to its anticonvulsant properties. *TCA* - **Tricyclic antidepressants (TCAs)** primarily work by inhibiting the reuptake of **norepinephrine** and **serotonin** in the brain. - They do not directly inhibit GABA transaminase but rather modulate monoamine neurotransmission. *Sertraline* - **Sertraline** is a **selective serotonin reuptake inhibitor (SSRI)** that works by blocking the reabsorption of **serotonin** into presynaptic neurons. - Its primary mechanism of action is focused on serotonin pathways, not on GABA metabolism. *Gabapentin* - **Gabapentin** is an anticonvulsant that is thought to exert its effects by modulating **calcium channels** and increasing **GABA synthesis**, but it is not a direct inhibitor of GABA transaminase. - Its mechanism of action is distinct from directly preventing GABA breakdown.
Question 83: Most clinically significant side effect of topiramate requiring immediate medical attention?
- A. Weight loss
- B. Visual impairment (Correct Answer)
- C. Insomnia
- D. Hemolysis
Explanation: ***Visual impairment*** - Topiramate can cause **acute angle-closure glaucoma**, a medical emergency that typically occurs within the **first month of therapy**. - Mechanism: Topiramate causes **ciliary body swelling** and **uveal effusion**, leading to anterior rotation of the iris-lens diaphragm and angle closure. - Clinical presentation: Rapid-onset **blurred vision**, **eye pain**, **headache**, **redness**, and may progress to permanent vision loss if untreated. - Management: **Immediate discontinuation** of topiramate and urgent **ophthalmology referral** for intraocular pressure management. *Weight loss* - Weight loss is a common and often desired side effect of topiramate, related to its effect on **appetite suppression** and enhanced satiety. - While it can be significant, it does not typically require immediate medical attention unless it becomes excessive or leads to nutritional deficiencies. - This side effect is sometimes therapeutically exploited in migraine prophylaxis. *Insomnia* - Insomnia is a known side effect of topiramate and can impact quality of life but is generally not life-threatening or an immediate medical emergency. - Management often involves adjusting the dosage, timing of administration (dosing earlier in the day), or prescribing sleep aids. *Hemolysis* - Hemolysis is **not a recognized side effect** of topiramate. - Topiramate is not known to directly cause the destruction of red blood cells. - Other serious side effects of topiramate include metabolic acidosis, kidney stones, and cognitive impairment, but not hemolysis.
Question 84: What serious side effect may lead to the discontinuation of felbamate?
- A. Seizures
- B. Renal impairment
- C. Gastrointestinal disorder
- D. Aplastic anemia (Correct Answer)
Explanation: ***Aplastic anemia*** - Felbamate is known to cause **aplastic anemia**, a severe and life-threatening condition where the **bone marrow stops producing enough new blood cells**. - Felbamate carries a **black box warning** for both aplastic anemia and **hepatotoxicity (severe liver failure)**, which are the two most serious adverse effects leading to discontinuation. - Due to this significant risk, felbamate is reserved for severe, refractory epilepsy cases, and patients require **regular monitoring** of blood counts and liver function tests. *Renal impairment* - While some medications can cause renal impairment, **felbamate is not primarily associated** with this side effect to the extent of requiring discontinuation. - Its metabolism and excretion are predominantly **hepatic (liver)**, and renal effects are less common or severe. *Gastrointestinal disorder* - Gastrointestinal side effects like nausea or vomiting are **common with many medications**, including felbamate, but are generally **mild and manageable**, rarely leading to discontinuation. - These effects are usually **dose-dependent** and can often be mitigated with supportive care. *Seizures* - Felbamate is an **antiepileptic drug (AED)**, so it is used to treat seizures, not cause them. - If a patient experiences seizures while on felbamate, it usually indicates **inadequate treatment response** or seizure exacerbation, rather than a direct side effect necessitating discontinuation for toxicity.
Question 85: Which of the following is NOT typically produced by local anesthetics?
- A. Muscle relaxation
- B. Euphoria
- C. Dysphoria (Correct Answer)
- D. Analgesia
Explanation: Detailed Analysis: ***Dysphoria*** - While local anesthetics can cause a range of central nervous system effects with toxicity, **dysphoria** (a state of unease or generalized dissatisfaction with life) is not a typical or primary direct effect of their action on receptors. High doses or systemic absorption might lead to anxiety and restlessness, but dysphoria specifically is uncommon. - The primary mechanism of local anesthetics involves blocking **voltage-gated sodium channels** [1], leading to a reversible loss of sensation, not directly causing mood disturbances like dysphoria. *Euphoria* - **Euphoria** can sometimes be observed with systemic local anesthetic toxicity due to initial CNS stimulation before depression. Some individuals report a transient feeling of well-being or altered mental status with high systemic levels of certain local anesthetics. - This effect is not a direct therapeutic goal but rather an **adverse reaction** associated with systemic absorption and CNS excitation. *Analgesia* - **Analgesia** is the primary therapeutic effect of local anesthetics, achieved by blocking nerve impulse transmission. This prevents the sensation of pain from reaching the brain [1]. - They work by **blocking sodium channels** in nerve membranes [1], thereby inhibiting the initiation and propagation of action potentials [2]. *Muscle relaxation* - **Muscle relaxation** in the area of blockade is a direct consequence of the local anesthetic's action on the motor nerves supplying the muscles. - By blocking nerve conduction in **motor nerve fibers** [1], local anesthetics prevent muscle contraction, leading to temporary skeletal muscle paralysis.
Question 86: Which of the following is a benzylisoquinoline muscle relaxant?
- A. Rocuronium
- B. Doxacurium (Correct Answer)
- C. Pancuronium
- D. Vecuronium
Explanation: ***Doxacurium*** - **Doxacurium** is a long-acting, non-depolarizing neuromuscular blocker classified as a **benzylisoquinoline** compound [1]. - These agents are known for their minimal cardiovascular effects and lack of histamine release in therapeutic doses [1]. *Vecuronium* - **Vecuronium** is an **aminosteroid** non-depolarizing neuromuscular blocker [2]. - It is known for its intermediate duration of action and minimal cardiovascular effects [1]. *Rocuronium* - **Rocuronium** is also an **aminosteroid** non-depolarizing neuromuscular blocker [2]. - It has a rapid onset of action, making it suitable for rapid sequence intubation, and can be reversed by **sugammadex**. *Pancuronium* - **Pancuronium** is an **aminosteroid** non-depolarizing neuromuscular blocker with a long duration of action [1]. - It is associated with a vagolytic effect that can cause an increase in **heart rate** and **blood pressure** [1].
Question 87: Which medication increases insulin secretion from beta cells?
- A. Metformin
- B. Repaglinide (Correct Answer)
- C. Pioglitazone
- D. Pramlintide
Explanation: ***Repaglinide*** - This medication is a **meglitinide analog** that stimulates **insulin release** from pancreatic beta cells by closing ATP-sensitive potassium channels. - Its fast onset and short duration of action make it particularly useful for controlling **postprandial glucose** excursions. *Metformin* - This medication primarily works by **decreasing hepatic glucose production** and improving insulin sensitivity in peripheral tissues. - It does **not directly stimulate insulin secretion** from beta cells; thus, it carries a lower risk of hypoglycemia compared to sulfonylureas or meglitinides. *Pramlintide* - This is an **amylin analog** that works by slowing gastric emptying, suppressing postprandial glucagon secretion, and increasing satiety. - It is an **injectable medication** used as an adjunct to insulin therapy and does not directly enhance insulin secretion from beta cells. *Pioglitazone* - This drug is a **thiazolidinedione** that improves insulin sensitivity in target tissues (e.g., muscle, fat, liver) by activating **peroxisome proliferator-activated receptor-gamma (PPAR-γ)**. - While it improves the body's response to insulin, it does **not directly stimulate insulin secretion** from the beta cells.
Question 88: Which of the following antidiabetic drugs (other than insulin) is indicated as adjunct therapy for the management of both type I and type II diabetes mellitus?
- A. Sulphonylureas
- B. Metformin
- C. Acarbose
- D. Pramlintide (Correct Answer)
Explanation: Pramlintide - Pramlintide is an amylin analog indicated as an adjunct therapy to insulin for both type 1 and type 2 diabetes, helping to regulate post-prandial glucose. - It slows gastric emptying, suppresses postprandial glucagon secretion, and promotes satiety, leading to reduced insulin requirements and improved glycemic control. Sulphonylureas - Sulphonylureas primarily stimulate insulin secretion from pancreatic beta cells, making them effective only in Type 2 diabetes where some beta-cell function is preserved [2]. - They are not indicated for Type 1 diabetes because these patients have absolute insulin deficiency due to beta cell destruction. Metformin - Metformin is a biguanide that primarily reduces hepatic glucose production and improves insulin sensitivity in peripheral tissues. - It is a first-line treatment for Type 2 diabetes but is generally not used for Type 1 diabetes as it does not address the fundamental lack of insulin. Acarbose - Acarbose is an alpha-glucosidase inhibitor that works by delaying carbohydrate absorption from the gastrointestinal tract, thus reducing postprandial glucose spikes [1]. - While it can be used in Type 2 diabetes to manage postprandial hyperglycemia, it is not typically indicated as an adjunct for Type 1 diabetes alongside insulin [3].
Question 89: Which of the following statements about sitagliptin is false?
- A. Used in type II diabetes mellitus
- B. Cannot be used orally (Correct Answer)
- C. Used in combination with other oral hypoglycemic agents
- D. All of the above statements are true
Explanation: ***Cannot be used orally*** - This statement is **false** because **sitagliptin** is an **oral medication** approved for the treatment of type 2 diabetes mellitus. - As a **DPP-4 inhibitor**, it is designed to be taken by mouth to increase incretin hormone levels. *Used in type II diabetes mellitus* - This statement is **true** as **sitagliptin** is a commonly prescribed **oral antidiabetic drug** for the management of type 2 diabetes. - It works by inhibiting the enzyme **dipeptidyl peptidase-4 (DPP-4)**, which increases levels of **GLP-1** and **GIP** to enhance insulin secretion and reduce glucagon secretion. *Used in combination with other oral hypoglycemic agents* - This statement is **true** as **sitagliptin** is often used as **add-on therapy** with other oral hypoglycemic agents like **metformin** or a **sulfonylurea** when monotherapy is insufficient. - This combination approach helps achieve better glycemic control by targeting different mechanisms of action. *All of the above statements are true* - This statement is **false** because the first statement "Cannot be used orally" is incorrect. - Since sitagliptin is indeed an oral medication, not all the above statements are true, making this option incorrect.
Question 90: What is a potential risk associated with the use of thiazolidinediones in the treatment of type 2 diabetes?
- A. Heart failure (Correct Answer)
- B. Pulmonary fibrosis
- C. Myocarditis
- D. Renal dysfunction
Explanation: ***Heart failure*** - Thiazolidinediones (TZDs), such as **pioglitazone** and **rosiglitazone**, can cause **fluid retention** and **volume expansion**, which may precipitate or worsen congestive heart failure. - This risk is higher in patients with pre-existing cardiac conditions and is a significant concern for these drugs. *Pulmonary fibrosis* - **Pulmonary fibrosis** is not a known or common adverse effect associated with thiazolidinedione use. - This condition is typically linked to certain other medications (e.g., **amiodarone**, **methotrexate**) or systemic diseases. *Myocarditis* - **Myocarditis**, inflammation of the heart muscle, is not a recognized side effect of thiazolidinediones. - Myocarditis is more commonly caused by viral infections, autoimmune diseases, or hypersensitivity reactions to certain drugs, but not TZDs. *Renal dysfunction* - While TZDs can cause fluid retention, they do not directly cause **renal dysfunction** or damage the kidneys. - In fact, some studies suggest they may have renoprotective effects due to reduced proteinuria, although fluid balance needs careful monitoring in patients with impaired renal function.