Can Edrophonium cross the blood-brain barrier?

Edrophonium is a quaternary ammonium compound that is primarily used as a diagnostic agent for myasthenia gravis. One of the key characteristics of quaternary ammonium compounds is their ionic nature, which limits their ability to penetrate lipid membranes, including the blood-brain barrier. This barrier is designed to protect the central nervous system from potentially harmful substances, allowing only certain molecules to cross.

Since edrophonium is charged, it does not readily cross the blood-brain barrier under normal circumstances. This characteristic is significant in its pharmacological use, as it primarily exerts its effects peripherally rather than centrally. This is essential for its function in treating conditions like myasthenia gravis without causing central nervous system side effects.

In contrast, compounds that are uncharged or have the ability to pass through lipid membranes can effectively reach the central nervous system, which is not the case for edrophonium. Therefore, the conclusion is that edrophonium cannot cross the blood-brain barrier, making this the correct answer.