Dimenhydrinate (DMH) is used for the prevention and treatment of nausea, vomiting, dizziness and vertigo associated with motion sickness in a dose of 50 mg 1. It’s made of two drugs in a form of salt, diphenhydramine and 8-chlorotheophylline which synergically decrease motion caused neural excitation 2. DMH is classified as a slightly soluble drug and it belongs to class II of BCS classification as a drug with low solubility and high permeability 3. Cyclodextrins (CDs) are cyclic oligosaccharides formed by α-1,4-linked glucose units with a hydrophilic outer surface and a lipophilic central cavity. Formation of inclusion complex by incorporating a drug in the central CD cavity provides improvement of physicochemical properties without molecular modifications. Solubility and dissolution rate of poorly water-soluble drugs can be increased 4. Aqueous solubility of natural CDs is limited due to their tendency to form H-bonded associations. However, due to multiple reactive hydroxyl groups, their functionality can be greatly increased by chemical modification 5. CDs’ substituted derivates can overcome poor solubility issues and enhance bioavailability. Hydroxypropylβ-CD (HP-β-CD) has good inclusion ability, high water solubility and it’s safe for intravenous and oral administration 6. Stability constant (Ks) and complexation efficacy (CE) are important for assessing the binding characteristics of the drug and CD. They can be determined by the phase solubility studies where the change of the drug solubility is corresponding to the concentration of CD 7. Linear (AL) type of the curve implies that one molecule of the drug forms inclusion complex with one molecule of the CD. Apparent stability constant K1:1 can be calculated from the following equation:

Microneedles (MNs) represent the concept of attractive, minimally invasive puncture devices of micron-sized dimensions that penetrate the skin painlessly and thus facilitate the transdermal administration of a wide range of active substances. MNs have been manufactured by a variety of production technologies, from a range of materials, but most of these manufacturing methods are time-consuming and expensive for screening new designs and making any modifications. Additive manufacturing (AM) has become one of the most revolutionary tools in the pharmaceutical field, with its unique ability to manufacture personalized dosage forms and patient-specific medical devices such as MNs. This review aims to summarize various 3D printing technologies that can produce MNs from digital models in a single step, including a survey on their benefits and drawbacks. In addition, this paper highlights current research in the field of 3D printed MN-assisted transdermal drug delivery systems and analyzes parameters affecting the mechanical properties of 3D printed MNs. The current regulatory framework associated with 3D printed MNs as well as different methods for the analysis and evaluation of 3D printed MN properties are outlined.

Microneedles (MNs) have been manufactured using a variety of methods from a range of materials, but most of them are expensive and time-consuming for screening new designs and making any modifications. Therefore, stereolithography (SLA) has emerged as a promising approach for MN fabrication due to its numerous advantages, including simplicity, low cost, and the ability to manufacture complex geometrical products at any time, including modifications to the original designs. This work aimed to print MNs using SLA technology and investigate the effects of post-printing curing conditions on the mechanical properties of 3D-printed MNs. Solid MNs were designed using CAD software and printed with grey resin (Formlabs, UK) using Form 3 printer (Formlabs, UK). MNs dimensions were 1.2 × 0.4 × 0.05 mm, arranged in 6 rows and 6 columns on a 10 × 10 mm baseplate. MNs were then immersed in an isopropyl alcohol bath to remove unpolymerized resin residues and cured in a UV-A heated chamber (Formlabs, UK). In total, nine samples were taken for each combination of curing temperature (35°C, 50°C, and 70°C) and curing time (5 min, 20 min, and 60 min). Fracture tests were conducted using a hardness apparatus TB24 (Erweka, Germany). MNs were placed on the moving probe of the machine and compressed until fracture. The optimization of the SLA process parameters for improving the strength of MNs was performed using the Taguchi method. The design of experiments was carried out based on the Taguchi L9 orthogonal array. Experimental results showed that the curing temperature has a significant influence on MN strength improvements. Improvement of the MN strength can be achieved by increasing the curing temperature and curing time.