Abstract
The effectiveness in transdermal delivery of skin permeation strategies (e.g., chemical enhancers, vesicular carrier systems, sonophoresis, iontophoresis, and electroporation) is poorly investigated outside of laboratory. In therapeutic application, the lack of recognized techniques for measuring the actually-released drug affects the scientific concept itself of dosage for topically- and transdermally-delivered drugs. Here we prove the suitability of impedance measurement for assessing the amount of drug penetrated into the skin after transdermal delivery. In particular, the measured amount of drug depends linearly on the impedance magnitude variation normalized to the pre-treated value. Three experimental campaigns, based on the electrical analysis of the biological tissue behavior due to the drug delivery, are reported: (i) laboratory emulation on eggplants, (ii) ex-vivo tests on pig ears, and finally (iii) in-vivo tests on human volunteers. Results point out that the amount of delivered drug can be assessed by reasonable metrological performance through a unique measurement of the impedance magnitude at one single frequency. In particular, in-vivo results point out sensitivity of 23 ml−1, repeatability of 0.3%, non-linearity of 3.3%, and accuracy of 5.7%. Finally, the measurement resolution of 0.20 ml is compatible with clinical administration standards.
Highlights
The effectiveness in transdermal delivery of skin permeation strategies is poorly investigated outside of laboratory
Topical administration and transdermal delivery are advantageous in comparison with systemic administration routes because complications as first-pass metabolism, toxicity, and side effects are attenuated for the patient[2]
In case of a peeled eggplant, the uncertainty sources are not masked by a stratum corneum
Summary
Metrological characteristics of in-vivo tests are compared with laboratory, and ex-vivo performance in Table 4 for the same setup configuration, drug and sample size (8): (i) sensitivity is comparable, decreased with respect to values, owing to the higher viscosity of the solution injected in in-vivo tests; (ii) nonlinearity is lower than in ex-vivo tests (3.31% vs 4.25%), though still slightly higher than in laboratory (2.35%); (iii) 1 −σ repeatability slightly worsens from 0.16% to 0.27% (though still again worse than in laboratory, 0.07%); (iv) the accuracy improves from 7.40 to 5.71%, and is still compatible with laboratory (5.23%); and (v) analogously, the resolution improves from 0.37 to 0.19 ml, even higher than in laboratory (0.23 ml) Such results highlight the suitability of impedance measurement for assessing the amount of drug penetrated into the skin after in-vivo treatment
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