The blood brain barrier protects the brain from harmful molecules and also prohibits certain drugs to cross as well. Only drugs who are hydrophobic are allowed to pass, while those that are...

The blood brain barrier protects the brain from harmful molecules and also prohibits
certain drugs to cross as well. Only drugs who are hydrophobic are allowed to pass,
while those that are hydrophilic are kept out.

why are hydrophobic ones Allowed to pass, they have a competitive inhibitor? Explain