Compare histamine and mecholyl in common ion transfer by the continuous galvanic current. All of the following apply to mecholyl EXCEPT

• A. Produces a more intense local counterirritation
• B. Deposited in deeper layers of the skin and is more gradually absorbed
• C. Systemic effects occur as a rule and more often
• D. Gives best results in joint affectations, peptic ulcer disease, and in varicose ulcers

Answer: (A)

In iontophoresis with a continuous galvanic current, histamine and mecholyl behave differently in how they affect skin and systemic activity. Histamine tends to cause a strong local reaction at the application site—marked redness and irritation—so it produces a very intense local counterirritation. Mecholyl, on the other hand, tends to deposit in deeper layers of the skin and is absorbed more gradually, which aligns with a milder local reaction but a greater potential for systemic effects because it’s a cholinergic agent. Because methacholine (mecholyl) can be absorbed systemically more readily, systemic effects occur more often with it than with histamine. Clinically, mecholyl iontophoresis has been described as giving best results in conditions like joint involvement, peptic ulcers, and varicose ulcers. Therefore, the statement that mecholyl produces a more intense local counterirritation is not correct.