Pharmacology

Concept: Vitamin K is a fat-soluble vitamin that plays a crucial role in the synthesis of blood clotting factors. It is essential for the proper functioning of the coagulation system in the human body. Vitamin K is required in the liver for the synthesis of several clotting factors, including:

• Factor II (Prothrombin)
• Factor VII
• Factor IX
• Factor X

These clotting factors help in the formation of blood clots and prevent excessive bleeding when a blood vessel is injured.
Step 1: Understanding the role of Vitamin K in coagulation.
Vitamin K acts as a cofactor for the enzyme responsible for the carboxylation of glutamic acid residues in clotting factors. This modification allows the clotting factors to bind calcium ions, which is essential for the blood clotting process. Without Vitamin K, these clotting proteins remain inactive, leading to impaired blood coagulation.
Step 2: Effects of Vitamin K deficiency.
Deficiency of Vitamin K can result in:

• Prolonged bleeding time
• Hemorrhage
• Delayed blood clotting

Newborn infants are particularly at risk of Vitamin K deficiency, which is why Vitamin K injections are often given after birth to prevent hemorrhagic disease of the newborn.
Step 3: Evaluating the options.

• Vitamin A: Important for vision and immune function.
• Vitamin C: Essential for collagen synthesis and wound healing.
• Vitamin D: Regulates calcium and phosphorus metabolism.
• Vitamin K: Essential for synthesis of blood clotting factors. (Correct)

Thus, the vitamin required for the synthesis of blood clotting factors is:

Concept: Omeprazole is a widely used drug for the treatment of acid-related disorders such as peptic ulcer disease, gastroesophageal reflux disease (GERD), Zollinger–Ellison syndrome, and gastric ulcers. It belongs to a class of drugs known as Proton Pump Inhibitors (PPIs). Proton pump inhibitors work by suppressing the production of gastric acid in the stomach. Omeprazole specifically blocks the enzyme responsible for the final step of acid secretion in the stomach.
Step 1: Understanding the target enzyme.
In the stomach, acid secretion is carried out by the parietal cells. These cells contain an enzyme called the H /K –ATPase enzyme, also known as the proton pump. This enzyme exchanges hydrogen ions (H ) with potassium ions (K ) and releases hydrogen ions into the gastric lumen, forming hydrochloric acid (HCl). Omeprazole inhibits this enzyme, thereby reducing gastric acid secretion.
Step 2: Mechanism of action of Omeprazole.

• Omeprazole is a prodrug that becomes activated in the acidic environment of the stomach.
• It binds irreversibly to the H /K –ATPase enzyme in parietal cells.
• This blocks the final step of gastric acid secretion.
• As a result, the amount of acid produced in the stomach is significantly reduced.

Because it blocks the final step of acid secretion, Omeprazole is considered highly effective in reducing stomach acidity.
Step 3: Evaluating the options.

• H receptor antagonist: Drugs like ranitidine and famotidine belong to this class.
• Proton pump inhibitor: Omeprazole belongs to this class and inhibits H /K –ATPase. (Correct)
• Anticholinergic agent: Reduces gastric secretions by blocking acetylcholine.
• Antacid: Neutralizes gastric acid but does not inhibit acid production.

Therefore, the correct answer is:

Concept: Selective Serotonin Reuptake Inhibitors (SSRIs) are a class of antidepressant drugs commonly used to treat mental health disorders such as depression, anxiety disorders, obsessive–compulsive disorder (OCD), and panic disorders. SSRIs work by inhibiting the reuptake of serotonin (5-HT) in the brain. Normally, serotonin released into the synaptic cleft is reabsorbed back into the presynaptic neuron. SSRIs block this reuptake process, thereby increasing the availability of serotonin in the synaptic space. This enhanced serotonin activity improves mood and emotional stability. Common examples of SSRIs include:

• Fluoxetine
• Sertraline
• Paroxetine
• Citalopram
• Escitalopram

Step 1: Understanding the mechanism of SSRIs.
SSRIs selectively inhibit the serotonin transporter responsible for reuptake. As a result:

• Serotonin concentration in the synaptic cleft increases.
• Neurotransmission of serotonin is prolonged.
• Symptoms of depression and anxiety are reduced.

Because of their selectivity, SSRIs generally produce fewer side effects compared with older antidepressants.
Step 2: Identifying the SSRI among the given drugs.

• Fluoxetine: A well-known SSRI antidepressant used for depression, OCD, and anxiety disorders.
• Amitriptyline: A tricyclic antidepressant (TCA), not an SSRI.
• Haloperidol: A typical antipsychotic used in schizophrenia.
• Diazepam: A benzodiazepine used as an anxiolytic and sedative.

Thus, the drug belonging to the SSRI class is Fluoxetine.
Step 3: Conclusion.
Since Fluoxetine selectively inhibits serotonin reuptake and is widely used as an antidepressant, the correct answer is: