Which of the following statements regarding transfer of drugs across placenta is FALSE ?
**Core Concept**
The transfer of drugs across the placenta is a critical aspect of fetal pharmacology, governed by the principles of diffusion and passive transport. The placental membrane's lipid solubility, molecular weight, and ionization state determine the ease of drug transfer.
**Why the Correct Answer is Right**
The placental transfer of a drug is influenced by its lipid solubility and molecular weight. Lipid-soluble drugs with low molecular weights can easily diffuse across the placental membrane, whereas ionized or polar molecules are restricted due to their low lipid solubility. This selective transfer is crucial in determining the fetal exposure to the drug.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it contradicts the established principle of placental transfer, where lipid-solubility plays a significant role in determining the ease of transfer.
**Option B:** This option is incorrect because it inaccurately suggests that molecular size is the primary determinant of placental transfer, whereas lipid solubility is the key factor.
**Option C:** This option is incorrect because it states a true principle of placental transfer, where ionized molecules are restricted due to their low lipid solubility.
**Clinical Pearl / High-Yield Fact**
When prescribing medications during pregnancy, it is essential to consider the potential impact on the fetus. The placental transfer of a drug can be influenced by factors such as maternal liver function, placental blood flow, and the presence of any placental abnormalities.
**Correct Answer: A. This option is incorrect because it contradicts the established principle of placental transfer, where lipid-solubility plays a significant role in determining the ease of transfer.**