Directly acting cough suppressant is :
**Core Concept**
The question is asking about a type of medication that directly suppresses coughing, as opposed to indirect cough suppressants that work on the underlying cause of coughing. This is a pharmacological principle related to the treatment of cough, specifically targeting the cough center in the brainstem.
**Why the Correct Answer is Right**
Directly acting cough suppressants work by stimulating the cough center in the brainstem, specifically the medulla oblongata, to suppress the cough reflex. These medications bind to opioid receptors in the cough center, which leads to the inhibition of coughing. Examples of directly acting cough suppressants include codeine and hydrocodone, which are opioids that stimulate the cough center to suppress coughing.
**Why Each Wrong Option is Incorrect**
**Option A:** Indirectly acting cough suppressants, such as antihistamines and decongestants, do not directly target the cough center in the brainstem.
**Option B:** Expectorants, such as guaifenesin, work by thinning and loosening mucus, making it easier to cough up, but do not directly suppress coughing.
**Option C:** Bronchodilators, such as albuterol, work by relaxing airway smooth muscle, but do not directly suppress coughing.
**Clinical Pearl / High-Yield Fact**
It's essential to note that directly acting cough suppressants can have significant side effects, such as respiratory depression, and should be used with caution.
**Correct Answer:** C. Codeine.