To administer procaine hydrochloride iontophoresis effectively, which current should be used?

Using continuous monophasic current with the medication under the anode is the correct approach for administering procaine hydrochloride iontophoresis effectively. This method takes advantage of the characteristics of procaine hydrochloride, which is a positively charged medication. By placing the medication under the anode, it ensures that the procaine is pushed toward the tissues through the positive charge, enhancing its penetration into the skin and targeted tissues.

Monophasic current, which flows in one direction, is particularly suited for iontophoresis as it helps to maintain a consistent delivery of the medication without reversing polarity. This stabilizes the process and enables better control over the ion movement of the drug.

In contrast, the other options either employ a different current type or incorrect placement of the medication, which would not optimize the delivery of procaine hydrochloride. For instance, placing the medication under the cathode or using a biphasic current would not facilitate the desired ion movement effectively, resulting in inadequate therapeutic effects. Thus, the use of a continuous monophasic current with positive polarity at the anode ensures the best therapeutic application for procaine hydrochloride iontophoresis.