Comparative analysis of the pharmacokinetic parameters of transdermal and injectable forms of nicotinamide

In recent years, oxidative stress, characterized by excess free radicals in the body, has been called the cause of many diseases. There is an active search for drugs with antioxidant properties that are suitable for long-term maintenance therapy. Nicotinamide (NAM), an antioxidant, is used to treat a variety of diseases, usually in oral or injectable form. Given the peculiarities of the drug regimen (dose, prolonged administration), a new dosage form of NAM, a microemulsion-based transdermal patch (TP), containing 20 mg/10 cm2 of NAM, has been proposed.The objective of this work is to compare the pharmacokinetic parameters of intramuscular and transdermal NAM administration in animal experiments for 24 hours.Materials and methods. We used laboratory samples of nicotinamide TP based on a microemulsion-based transdermal delivery emulsion (TDS) with different content of sodium docusate transfer activator. The pharmacokinetics of transdermal and intramuscular injections were studied in male Chinchilla rabbits weighing 3.5–4.0 kg. Plasma NAM levels of the experimental animals were determined by high-performance liquid chromatography using a specially designed method on NUCLEODUR PFP columns (5 μm, 250 × 4.6 mm) using the mobile phase acetonitrile: deionized water. The samples were preliminarily purified by solid-phase extraction using Chromabond C18 Hydra cartridges.Results. When administered intramuscularly, the maximum blood NAM level was 13.3±1 μg/mL; when NAM transdermal forms were applied in the same dosage with different contents of the transfer activator, the levels did not differ significantly – 3.1 and 3.2 μg/mL. It was shown that in transdermal administration of NAM, concentration of the active substance remained at a constant level for ~6 hours. The bioavailability of NAM with transdermal administration was calculated relative to intramuscular administration: 1.43 for TP with 9.8% docusate sodium and 1.84 with 3.3% docusate sodium.Conclusion. NAM has a higher bioavailability when administered transdermally at 20 mg than when administered intramuscularly in the same dose. With transdermal administration, NAM concentration can be maintained at a constant level for a long time, without the jumps that are typical of intramuscular administration.