Final answer:
Drugs that are permeable to the blood-brain barrier demonstrate certain characteristics such as high lipid solubility, low molecular weight, low affinity for plasma proteins, and the ability to mimic or utilize transport mechanisms for nutrients. These drugs can either pass through via passive diffusion or be actively transported across the barrier.
Step-by-step explanation:
The type of drug that is permeable to the blood-brain barrier (BBB) generally includes those with certain physiochemical properties conducive to passing through this selective barrier. Molecules that are small and non-polar, or those that mimic nutrients that have dedicated transport mechanisms, such as glucose or amino acids, are typically more likely to penetrate the BBB. Drugs with a high lipid solubility, low molecular weight, and those that are not strong substrates for efflux transporters like P-glycoprotein (PgP) are usually better at crossing the BBB. Moreover, drugs can be designed as prodrugs that target specific transporters like the L-type Amino Acid Transporter, which facilitates membrane transport of certain types of molecules.
Drugs with low polar surface area and properties that decrease hydrogen bonding potential are also known to better penetrate the BBB. Therefore, altering the physiochemical properties of a drug, such as increasing its lipophilicity, decreasing its polarity, or utilizing a prodrug approach targeting specific brain transporters, can enhance its ability to permeate the BBB and achieve therapeutic concentrations in the central nervous system (CNS).