A Science Based Approach to Topical Drug Classification System (TCS)

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Microneedles

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Microneedles (MNs) are small micron-sized needles which whenapplied on the skin breaches the SC to create microchannels throughthe skin thereby assisting drug delivery. Drug can be deliveredby variousmodes using these techniques. These modes are: (a) piercingan array of solidmicroneedles into the skin followed by application of adrug patch at the treated site (b) coating drug ontomicroneedlesand inserting them into the skin for subsequent dissolution of the coateddrug within the skin (c) encapsulating drug within biodegradable, polymericmicroneedles followed by insertion into the skin for controlleddrug release and   (d) injecting drug through hollow microneedles. The microchannels thus created help topically applied drugmolecules to by pass the SC which is the major rate limiting barrier for transdermal permeation.Moreovermicroneedles areminimally invasiveand painless as they do not penetrate up to the papillary dermis wherenerve endings are situated. In vivo ...
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Iontophoresis

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Ø   Iontophoresis is a method of transferring substances across the skin by applying an electrical potential difference. Ø   It promotes the transfer of charged ionic drugs and possibly high molecular weight substances such as peptides. Ø   Electric current is applied through two electrodes, placed in the patient’s skin. The first, or donor, electrode (cathode) delivers the negatively charged therapeutic agent (e.g., an organic acid), where as the second or receptor, electrode (anode) serves to close the circuit. Ø   This setup is named cathodal iontophoresis.For positively charged drugs (e.g., amines or peptides),the cell arrangement is reversed called anodal iontophoresis. The silver (anode) and silver chloride(cathode) electrode system utilized in both types of iontophoresis.      
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Microspheres

Microspheres Development of Floating Microspheres Floating microspheres are gastro-retentive drug delivery systems based on non-effervescent approach. Hollow microspheres are in strict sense, spherical empty particles without core. These microspheres are characteristically free flowing powders consisting of proteins or synthetic polymers, ideally having a size less than 200 micrometer. Solid biodegradable microspheres incorporating a drug dispersed or dissolved throughout particle matrix have the potential for controlled release of drugs. Gastro-retentive floating microspheres are low-density systems that have sufficient buoyancy to float over gastric contents and remain in stomach for prolonged period. As the system floats over gastric contents, the drug is released slowly at desired rate resulting in increased gastric retention with reduced fluctuations in plasma drug concentration. When microspheres come in contact with gastric fluid the gel formers, polysaccharides, and ...
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