FMGE 2018 — Pharmacology

12 Questions — Page 2 of 2

Q11

True for lithium:

Q12

Purpose of adding zinc to insulin in commercial preparations for treatment of diabetes mellitus is:-

FMGE 2018 - Pharmacology FMGE Practice Questions and MCQs

Question 11: True for lithium:

A. Can be given safely in renal dysfunction
B. Protein bound
C. Narrow therapeutic index (Correct Answer)
D. Delayed absorption

Explanation: ***Narrow therapeutic index*** - Lithium has a **narrow therapeutic index**, meaning the difference between its effective and toxic doses is small. - This necessitates **close monitoring of serum lithium levels** to ensure efficacy and prevent toxicity. *Can be given safely in renal dysfunction* - Lithium is **primarily excreted renally**, and its clearance is directly proportional to creatinine clearance. - Therefore, it **should be used with caution** (or avoided) in patients with renal dysfunction due to increased risk of toxicity. *Protein bound* - Lithium is **not protein-bound**; it exists as a free ion in the blood. - This characteristic contributes to its rapid distribution and excretion. *Delayed absorption* - Lithium is **rapidly and almost completely absorbed** from the gastrointestinal tract. - Peak plasma concentrations are usually reached within 1-2 hours for immediate-release preparations.

Question 12: Purpose of adding zinc to insulin in commercial preparations for treatment of diabetes mellitus is:-

A. To make it short acting
B. To make it fast acting
C. To make it long acting (Correct Answer)
D. Addition of zinc makes the insulin effective orally

Explanation: ***To make it long acting*** - **Zinc** is added to insulin formulations, particularly **neutral protamine Hagedorn (NPH) insulin**, to create larger crystal complexes [1]. - These larger complexes **slow down the absorption** of insulin from the subcutaneous injection site, thereby prolonging its duration of action [2]. *To make it short acting* - **Short-acting insulins** like regular insulin are not formulated with zinc, as their purpose is rapid onset and a shorter duration. - Adding zinc would counteract the desired rapid-acting pharmacokinetic profile. *To make it fast acting* - **Fast-acting insulins** (insulin analogs) have specific amino acid modifications that alter their self-association properties to ensure rapid absorption, not the addition of zinc [2]. - Zinc actually works against the goal of fast action by promoting aggregation. *Addition of zinc makes the insulin effective orally* - Insulin is a **peptide hormone** and is generally destroyed by digestive enzymes in the gastrointestinal tract, making oral administration ineffective regardless of zinc presence [3]. - Efforts to create oral insulin involve complex delivery systems, not simple zinc addition.