Anaphoresis

Anaphoresis is a term used in electrotherapy and pharmacology to describe the electrophoretic transport of ionic species toward the anode when an electric current is applied. It is one directional component of iontophoresis, complementing cataphoresis, which denotes transport toward the cathode.

Mechanism and scope: When an electrical field is applied, charged molecules migrate according to their charge. Anions (negatively charged ions) move toward the positive electrode, the anode. In iontophoresis, this movement can be used to enhance the delivery of negatively charged drugs across biological barriers such as skin or mucosa. The process is influenced by the drug’s charge and size, the medium, and the presence of electroosmosis—bulk fluid flow that can modify overall transport. Reactions at the electrode sites create local pH changes, with acid near the anode and base near the cathode, potentially affecting drug stability and tissue tolerance.

Applications: Anaphoresis is utilized to increase local drug concentrations in transdermal and transmucosal delivery. It is commonly employed for negatively charged therapeutics, including certain anti-inflammatories, antibiotics, and local anesthetics, often as part of iontophoretic devices. In practice, anaphoresis is typically used in conjunction with cataphoresis, with electrode polarity chosen to optimize delivery of a given drug.

Safety and limitations: Effective use requires careful control of current density, duration, and electrode placement to minimize skin irritation and pH-related effects. Not all drugs are suitable for anaphoresis, and tissue properties influence outcomes. See also iontophoresis and electrotherapy.