Current aspects of formulation efforts and pore lifetime related to microneedle treatment of skin

Abstract

Importance of this field The efficacy of microneedles in the area of transdermal drug delivery is well-documented. Multiple studies have shown that enhancement of skin permeation via creation of microscopic pores in the stratum corneum can greatly improve the delivery rates of drugs. However, skin pretreatment with microneedles is not the only factor affecting drug transport rates. Other factors including drug formulation and rate of micropore closure are also important for optimizing delivery via this route. Areas covered in this review This review aims at highlighting work that has been done in these areas, with an emphasis on drug formulation parameters that affect transdermal flux. What the reader will gain This review creates an appreciation for the many factors affecting microneedle-enhanced delivery. Most results clearly indicate that microneedle skin pretreatment by itself may have different effects on drug transport depending on the formulation used, and formulation characteristics have different effects on the transport through untreated skin and microneedle-treated skin. Several formulation approaches are reported to optimize microneedle-enhanced drug delivery, including cosolvent use, vesicular, nanoparticulate and gel systems. Take home message In addition to well-established factors that affect microneedle-assisted delivery (geometry, type of microneedles, etc), formulation and pore viability are also critical factors that must be considered.

Recovery of Skin Barrier After Stratum Corneum Removal by Microdermabrasion

“…In this study, stratum corneum recovered within just 12-24 h. This rapid recovery was probably facilitated by the choice of animal model and the small area of stratum corneum removal. Barrier recovery after exposure to chemical peels and microneedles was reported after 3 days (14,35).…”

Microneedles for drug delivery: trends and progress

“…The use of MN as a DD system is an important development as the potential to allow a wider scope of molecules to be transdermally delivered through the skin is greatly increased (Dhamech et al, 2010;Gittard et al, 2010;Milewski et al, 2010;Singh et al, 2010). The amount of drug that is delivered can also be increased.…”

Microneedles: an emerging transdermal drug delivery system

“…This approach was known as 'poke and flow' (Figure 3d), where after piercing the skin, drug was allowed to flow through hollow microneedles from the reservoir in the patch. [13] Wang et al developed hollow microneedle arrays with a drug reservoir. [41] Upon the application of external pressure on the reservoir, the microneedle system penetrates into the skin, followed by the release of the drug solution into the skin.…”

“…[10,12] Various chemical and physical approaches have been employed to improve drug penetration across the skin. [13] Chemical approaches include the use of penetration enhancers, like surfactants, fatty acids/esters and solvents to dissolve the stratum corneum lipid or to increase the solubility of drugs. Physical approaches, like electroporation, iontophoresis, magnetophoresis and sonophoresis, have been found suitable to create pathways for only a few drugs across the skin.…”