Drug that crosses placenta is :
**Core Concept**
The concept being tested here is the ability to differentiate between drugs that can cross the placenta and those that cannot. This is crucial in understanding the potential risks and benefits of medications during pregnancy. Drugs that can cross the placenta enter the fetal circulation and may affect fetal development or cause harm to the fetus.
**Why the Correct Answer is Right**
The correct answer is a drug that is lipid-soluble and has a low molecular weight. These characteristics allow the drug to easily diffuse across the placental membranes, which are composed of lipid bilayers. As a result, the drug can enter the fetal circulation and potentially cause harm to the fetus. Examples of such drugs include certain antibiotics, anticonvulsants, and antidepressants.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is a drug that is highly bound to plasma proteins and has a high molecular weight, making it unlikely to cross the placenta.
* **Option B:** This option is incorrect because it is a drug that is primarily excreted by the kidneys and does not have the necessary lipid solubility to cross the placenta.
* **Option C:** This option is incorrect because it is a drug that is highly metabolized by the liver and does not have the necessary properties to cross the placenta.
**Clinical Pearl / High-Yield Fact**
It's essential to note that even if a drug can cross the placenta, the risk to the fetus may be minimized by using the lowest effective dose and by carefully monitoring fetal well-being.
**Correct Answer: C. The drug is likely a lipid-soluble, low molecular weight compound that can easily diffuse across the placental membranes.**