Lactulose belongs to which therapeutic class?
Laxative
Antidepressant
Antipsychotic
Antidiabetic
The Correct Answer is A
Lactulose is a synthetic disaccharide consisting of galactose and fructose that remains unabsorbed in the small intestine. It functions as an osmotic agent, drawing water into the colonic lumen to soften stool and stimulate peristalsis. Additionally, it is used to manage hepatic encephalopathy by acidifying the gut and converting ammonia to unabsorbable ammonium ions. It is a vital medication for both gastrointestinal and hepatic disorders.
Rationale:
A. Laxative is the correct therapeutic class. Specifically, lactulose is an osmotic laxative. By increasing the osmotic pressure in the colon, it promotes fluid retention and increases bowel motility. It is commonly used for chronic constipation and is particularly effective when a soft stool is required to prevent straining during defecation in high-risk cardiac or surgical patients.
B. Antidepressants are medications used to treat mood disorders by modulating neurotransmitters like serotonin and norepinephrine. Lactulose has no pharmacological activity in the central nervous system related to mood regulation. It does not cross the blood-brain barrier in significant amounts and lacks affinity for monoamine transporters. Therefore, it has no utility in treating clinical depression.
C. Antipsychotics are used to manage symptoms of schizophrenia and bipolar disorder by blocking dopamine receptors. Lactulose is a sugar derivative that stays within the gastrointestinal tract and does not interact with dopaminergic pathways. Its therapeutic effects are restricted to osmotic and acid-base changes in the bowel, rendering it useless for the management of psychosis or hallucinations.
D. Antidiabetics are agents that lower blood glucose levels, such as metformin or insulin. Despite being a disaccharide, lactulose is not absorbed and therefore does not raise or lower serum glucose significantly. It is not used to treat hyperglycemia; in fact, diabetic patients must use it with caution as small amounts of free sugars may be present in the solution.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["1310.4"]
Explanation
Step 1 is to convert the weight from pounds (lbs) to kilograms (kg)
Weight in kg = 154 ÷ 2.2
154 ÷ 2.2 = 70
Result at this step = 70 kg
Step 2 is to calculate the total volume (mL) to be administered
Volume = Weight in kg × Dose (mL/kg)
70 × 0.06 = 4.2
Result at this step = 4.2 mL
Step 3 is to calculate the dose in units
Total Units = Total mL × Concentration (IU/mL)
4.2 × 312 = 1310.4
Result at this step = 1310.4
Step 4 is to round to the nearest tenth
1310.4 = 1310.4
Answer: 1310.4
Correct Answer is E
Explanation
Parasympathetic innervation of the heart is primarily mediated through the vagus nerve, which releases acetylcholine (ACh) onto the sinoatrial (SA) node. This chemical signal binds to muscarinic M2 receptors, triggering G-protein mediated changes in membrane potential. The resulting negative chronotropic effect slows the heart rate to maintain resting homeostasis and cardiac output efficiency during periods of low activity.
Rationale:
A. Decreasing permeability to potassium would lead to a buildup of positive charge inside the cell, causing depolarization rather than slowing the heart. This would make the cell more excitable and increase the heart rate. Acetylcholine acts to stabilize the membrane, not to make it more prone to reaching the threshold potential quickly.
B. While sodium channels are involved in the initial "funny" current of the pacemaker potential, closing them is not the primary mechanism of vagal hyperpolarization. The main inhibitory effect of acetylcholine relies on the movement of potassium ions out of the cell. Sodium channel modulation is a secondary effect compared to the direct potassium conductance increase.
C. Opening calcium channels would actually increase the rate of depolarization and strengthen muscular contraction. Acetylcholine actually inhibits the L-type calcium current in the nodal tissue to help slow the rate of firing. This choice incorrectly describes the ion flow and the resulting effect on the cardiac cycle timing.
D. Closing sodium channels would not lead to hypopolarization (becoming less negative). Furthermore, the vagus nerve's primary inhibitory action is not centered on simple sodium channel closure. The heart's response to acetylcholine is characterized by a significant membrane shift toward a more negative, stable state, which is the opposite of hypopolarization or depolarization.
E. Acetylcholine increases permeability to potassium in the sinus node by opening specialized GIRK (G-protein coupled inwardly rectifying potassium) channels. As potassium exits the cell, the membrane potential becomes more negative, a state called hyperpolarization. This moves the resting potential further from the threshold, effectively slowing the rate of pacemaker firing and heart rate.
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