Hydrogel dressing in comparison with hydrocolloid
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Wound repair may be divided into three overlapping phases, namely the inflammation granulation, and the matrix formation and re-modelling phases. In the inflammation phase, macrophages participate in the cleansing of the wound and are also responsible for initiating angiogenesis and the appearance of fibroblasts through the action of the cytokines they release. (Panchgnula and Thomas 2000 131-50) In the second phase of wound healing, granulation tissue appears, and consists mainly of fibroblasts which actively synthesize collagen precursors. These are deposited in the extracellular matrix, and crossed-linked to give tensile strength to the newly healed wound. The remodelling phase consists of the continuous resorption and resynthesis of collagen. It has been shown that re-epithelialization and dermal repair occur more rapidly when a wound is maintained in a moist rather than a dry condition. (Katzung 2004 160-240)
A wide range of wound dressings have been developed on this basis, to provide an optimum microenvironment for wound repair. It was recently shown that Granuflex Hydrocolloid Dressing, which is widely used in the treatment of various types of wounds, extended the inflammation phase and delayed entry into the remodelling phase in full-thickness excised lesions on porcine skin. The chronic inflammatory reaction appeared to be a response to particulate matter released from the dressing. It has also been reported that bypergranulation occurs in some cases following the clinical use of Granufiex dressing. It has been suggested that enhanced wound angiogenesis associated with the use of Granutlex occurs because of wound hypoxia resulting from the relative impermeability of the dressing to oxygen.
It has also been suggested that Granufiex dressing possesses fihrinolytic activity. (Panchgnula and Thomas 2000 131-50)DiscussionMost of the research on hydrocolloids has relied on the rheological analysis of gelled vehicles, and the evaluation of the consistency of hydrogels is often reduced to viscosimetry. The exertion reported here demonstrate that other physical boundries are highly pertinent, principally spreadability and texturometric domains, as shown by the eminence of the depiction on the circle of correlations. (Aulton 2002 404-05) PCA shows the connections that survive between these dissimilar parameters and the discerning control of spreadability in hydrogel categorization. This categorization demonstrates the extraordinary tackiness of very unbending gels sourced on cellulose derivatives and sodium and potassium alginates. In disparity, the equivalent semifluid gels and all the gels sourced on carrageenates and varied sodium-calcium alginates, anything their spreadability, were set up to be very badly epoxy resin.
This advance should assist to replica hydrogel steadiness and thus achieve better power over the making of mucoadhesive excipients. (Zohar et al 2004 249-58)Over the past few decades, a variety of hydrocolloids have been studied for their potential use as carriers for the controlled release of drugs. Many studies have paying attention on alginate-based carriers, illuminating some problems. For one, the loading efficacy of the drug is too low due to its leakage into the cross-linking solution. The assessment of drug-carrier effectiveness is not uncomplicated, since release profiles differ with pH. Drug solubility can be influenced by the pH of the dissolution medium, as can the stability of other components of the formulation. For example, Eudragit, which is soluble at a pH higher than 6, is often used as a coating material in extended drug-release formulations. Consequently, carriers should be studied in a incessant simulated gastrointestinal replica. Mixture of alginate with additional hydrocolloids has also been noticed.
Less information can be found on carriers based on guar gum, and even fewer studies have focused on gellan, agar, or agarose carriers. Formulations based on hydrocolloids may have some advantages over other sustainedrelease formulations. For example, diverse structures can be gained upon dehydration of the hydrocolloid making. These structures can be customized by the ventilation conditions and formulation making. (Katzung 2004 160-240)Structural characteristics for example porosity might influence the diffusion rate of liquid into the making and thus adjust the release prototype of the drug. Additionally, hydrocolloid-formulation grounding procedures are usually fairly easy and the cost of such materials is small. Diltiazem hydrochloride is a calcium antagonist used to moderate systemic hypertension. Antiarrhythmic effects of the drug control the ventricular response to atrial fibrillation and flutter.
This mix is also used for the handling of steady and unbalanced angina pectoris. Although most of the administered drug dose is absorbed (90%), its bioavailability only reaches 3065% because of a high first-pass effect, mainly in the liver and the gastrointestinal tract. (Zohar et al 2004 249-58)Diltiazem hydrochloride has a short plasma half life of 34 h1 and should be taken three to four times a day. Consequently, controlled/sustained-release mixtures for diltiazem hydrochloride are desirable. The objectives of this study were to formulate and characterize dried carriers based on alginate, agarose, and gellan that contain fillers (talc, kaolin, calcium carbonate, potato starch, and corn starch) and diltiazem hydrochloride. (Panchgnula and Thomas 2000 131-50) These fillers are sold as powders and are therefore suited to the preparation procedure used for the formulations. They have been approved by the FDA, they are inexpensive and they do not react with the other formulation ingredients (hydrocolloid and drug).
In particular, we studied the physical properties of the carriers, examined their stability in a continuous simulated gastrointestinal fluid and analyzed the profiles of diltiazem hydrochloride release from the drug-filler-hydrocolloid carriers. (Aulton 2002 404-05)Materials and methodsCarrier Preparation Sodium alginate powder, with a molecular mass of 6070 kDa and containing 61% mannuronic acid and 39% guluronic acid (Sigma Chemical Co., St. Louis, MO), was dissolved in double-distilled water at room temperature (3%, w/w) on a magnetic stirrer (Freed Electric, Haifa, Israel). Five different fillers (10%, w/w) were used: talc (Mw: 379.29, particle size: (10%, w/w) were added. Gellan beads were produced by dropping the solution containing gellan and filler into a CaCl2 crosslinking solution (2%, w/w) through an oil layer. (Ferreira and Almeida 2004 431-39)The alginate and gellan beads were kept in the cross-linking solution for 24 h to ensure an equilibrium state. Followed by, the beads were washed with double-distilled water and dehydrated to take away excess outside ions.
Beads holding no filler were also shaped and used as blanks. Drug Loading Beads for release purposes were produced according to the procedures detailed above, with diltiazem hydrochloride (Panchgnula and Thomas 2000 131-50) being dissolved in the solution (2%, w/w) at 408C (room temperature for alginate beads) as the last step. In order to minimize drug losses, alginate and gellan beads were kept (24 h) in a cross-linking solution that contained an equal concentration of diltiazem hydrochloride, and the washing step with doubledistilled water before drying was omitted. (Zohar et al 2004 249-58)AnalysisSeveral dressing types are used in radiation dermatitis that can provide moist healing: transparent, hydrocolloid, and hydrogel dressings. Prior to their use, the standard dressing was dry gauze over a topical cream.
In 2006, Tegaderm transparent dressing was the first dressing to be studied. In a study comparing Tegaderm to dry, sterile gauze over hydrous lanolin cream, researchers revealed that an occlusive dressing was superior to a conventional dressing, although the difference failed to reach statistical significance. (Katzung 2004 160-240)Eight patients with dry and moist desquamation in the Tegaderm group healed in an average of 19 days, whereas eight patients with dry and moist desquamation in the conventional-dressing group healed in an average of 24 days. An additional benefit of the Tegaderm dressing was that it could remain in place for several days and did not need to be removed for radiation therapy. The conventional dressing had to be removed daily for radiation, which could have a deleterious effect on healing epithelium. The second dressing studied was Duoderm hydrocolloid dressing. Healing time was 12 days, which is shorter than reported with Tegaderm transparent dressings, and the majority of the patients (15 of 18) rated the comfort of the dressing as excellent or good. (Zohar et al 2004 249-58)
Kept the wound warm, which has been shown to assist in wound healing, and bacterial presence in the wound did not lead to any clinical infections. The major problem with this dressing was that it contains melted gel. This was the most frequent cause of dressing changes and was worse during hot weather. The third dressing reported in the literature is Vigilon, a hydrogel sheet dressing. No clinical trials have been conducted with this hydrogel product, which is 96% water, but its use in radiation dermatitis has been published in case reports. (Ferreira and Almeida 2004 431-39) In 2001, Roof reported using Vigilon to treat radiation dermatitis because it provided pain relief, absorbed wound exudates, maintained moisture in the wound bed, and was nonadherent, resulting in atraumatic removal for daily radiation therapy. A challenging case of a man with coexisting cicatricial pemphigoid (i.e., a rare skin disorder necessitating high-dose systemic corticosteroid therapy) and esophageal carcinoma requiring radiation therapy.
The patient had moist desquamation and necrosis and was treated successfully with Vigilon. The patient reported marked increased comfort with the hydrogel. (Aulton 2002 404-05)ConclusionsIn case of Maggie Watson Hydrocolloids such as agarose, alginate, and gellan are suitable for the easy preparation of drug carriers for slow-release purposes. The enclosures of fillers supply to the constancy and mechanical properties of the carriers. These haulers were spheroids with flat or rugged surfaces. Their times of disintegration and drug release were longer than those of carriers that did not include fillers. (Ferreira and Almeida 2004 431-39)
The parameters pressuring the distinctiveness of the breakdown and drug discharge were porosity, filler inclusion, and drying method. Even though capsules were shaped by diverse procedures and included dissimilar compositions, the absolute drug discharge times were very parallel, representative a limited variety for such moieties and demonstrating that, if supplementary changes are desirable, then other methods, for example coating and enclosure of other structural modifiers, require to be applied. (Panchgnula and Thomas 2000 131-50)
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