Gastrointestinal Drugs and Medications Q 19



Which category of drugs prevents/treats constipation by the osmotic drawing of water from extravascular space to intestinal lumen?
  
     A. Stimulants
     B. Bulk-forming agents
     C. Hyperosmotic agents
     D. Lubricants
    
    

Correct Answer: C. Hyperosmotic agents

Hyperosmotic agents change the osmotic gradient between the intestine and extravascular space causing water to move into the intestinal lumen and balance the gradient. Hyperosmotic agents reduce intraocular pressure by creating an osmotic gradient between the blood and the intraocular fluid compartments that causes fluid to shift from the eye to the blood. These agents are most effective when used for a short period of time. Systemic side effects and a limited period of efficacy in maintaining a reduction in intraocular pressure preclude their chronic use in the treatment of glaucoma.

Option A: Caffeine has a unique mechanism as a stimulant as it works as an inhibitor at the adenosine receptors. Agonism at these receptors induces a sensation of drowsiness, and therefore inhibition at these receptors leads to increased energy levels. The general mechanism of action of amphetamines is the induction of catecholamines, specifically norepinephrine and dopamine. These catecholamines lead to increased energy levels, euphoria, increased libido, and higher cognition. The induction of most of the effects of cocaine is through the blockade of the dopamine transporter protein. This results in increased dopamine levels at the synaptic cleft, and hence the effects of dopamine become amplified.
Option B: Bulk-forming laxatives absorb liquid in the intestines. This creates a bulky, more liquid-like stool that’s softer and easier to pass. Common bulk-forming laxatives include psyllium (Metamucil), polycarbophil (FiberCon), and methylcellulose (Citrucel). Bulk-forming laxatives are different from these laxatives. They’re most similar to stool softeners in that they help the bowels retain water. Unlike stimulant laxatives, they don’t stimulate nerves that speed up the movement of bowels through the intestines. They also don’t lubricate the stools like lubricant laxatives do. Osmotic laxatives differs from bulk-forming types by helping the intestines — not the bowels — retain water.
Option D: Lubricant is a substance which is used to control (more often to reduce) friction and wear of the surfaces in a contact of the bodies in relative motion [1]. Depending on its nature, lubricants are also used to eliminate heat and wear debris, supply additives into the contact, transmit power, protect, seal.