Resorcinol pastes

The formulations for resorcinol paste most often used in the past are shovm in Table 24.1. The preparation of this paste involves a lot of work for the pharmacist, who has to use centrifugation and/or ultrasound. The resorcinol crystals have to be thoroughly ground in a mortar before making up the paste to make sure no big crystals remain in it. The resulting mixture will be more homogenous and easier to spread. Unna s paste does not remain active very long, as it oxidizes rapidly. The doctor should therefore always use a freshly made paste. Another formulation contains resorcinol, olive oil, kaolin, zinc oxide, petrolatum and wool fat. 

The best results are achieved when the skin has been prepared for 15 days beforehand see Chapter 2. If the skin has been prepared with tretinoin or alpha-hydroxy acids (AHAs), if the patient has used products (benzoyl peroxide) or techniques (scrub, or abrasion with a massage glove) that increase the permeability of the stratum corneum, the resorcinol paste should not be left on too long. 

Resorcinol paste is compact and dilEcult to apply. It is easily softened by putting it in a bain-marie at 45° for around 10 minutes. If that is not possible, small blocks of paste should be applied to the patient s skin. Heat from the skin will slowly melt the paste and make it easier to spread, although the resorcinol may penetrate too deeply where contact time has been longer. 

On the jaw area, as with phenol, the paste is applied up to 2 cm below the upper jaw. The paste should be rubbed gently to make it more homogenous. Resorcinol paste is often applied on the decoUetage and back. Great care must be taken in these areas, however, as the extent of the surface area treated can induce toxicity. Large surface areas should be treated in several stages, and a rest period between two applications will help the body eliminate the metabolites from the detoxification of this phenol compound. 

First application (first day) contact time 10-25 minutes. A few minutes after the first application, the patient feels some heat and then a tolerable burning sensation. This sensation starts where the resorcinol has penetrated most rapidly. The cheeks are usually more permeable than the forehead. The areas where the patient first feels burning are the first to be cleaned of the resorcinol paste at the end of the peel. The sensation of acid burning can sometimes become intense, and a yellow serous fluid may be seen to weep through the partially lysed epidermis. In this case, the patient should be given an analgesic for the first night paracetamol (acetaminophen) plus codeine. 

According to Unna, the resorcinol paste can be applied again as soon as flaking has finished. We are rarely called upon to repeat an application of resorcinol paste nowadays. The results of an Unna s paste peel remain modest in relation to the complexity of the treatment and the downtime involved, and patients are not prepared to accept these conditions. 

Unique methods based on new principles have been developed within the past 10 years. Threonine (27,28,249) is oxidized by lead tetraacetate or periodic acid to acetaldehyde, which is determined by photometric analysis of its p-hydroxydiphenyl complex or iodometric titration of its combined bisulfite. Serine is oxidized similarly to formaldehyde, which is determined gravimetrically (207) as its dimedon (5,5-dimethyldihydro-resorcinol) derivative or photometric analysis (31) of the complex formed with Eegriwe s reagent (l,8-dihydroxynaphthalene-3,5-disulfonic acid). It appears that the data obtained for threonine and serine in various proteins by these oxidation procedures are reasonably accurate. [Block and Bolling (26) have given data on the threonine and serine content of various proteins. ]... 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

A good example of a back titration involving iodine and thiosulfate is the assay of resorcinol in Resorcinol Solution BP. Resorcinol is an antiseptic that was widely used in the past, although less so now. The assay of resorcinol involves a quantitative electrophilic aromatic substitution reaction using bromine as the reagent, as shown in Figure 6.4. 

Resorcinol in paste form is used in a very specific manner the paste is usually applied three times, once a day for 3 days in a row. Post-peel care is very important diuing the following week the skin should not be hydrated at all, as it has to dry out completely for the peel to be effective and, above all, the patient must not pull off or pick at the flaking skin. Only the doctor can safely cut off any strips of flaking skin with sterile scissors. Cosmeceutical creams for age spots, acne, aging or sagging skin, etc. should only be applied after the skin has flaked. Effective sun protection (UVA + UVB + HSP inducers) is absolutely essential for approximately 6 weeks after the peel. 

Resorcinol is used in many antipruritic formulations, especially in chronic kidney dialysis. It is mainly used in paste... 

Third application (third day) contact time 30-35 minutes. The third application must be carried out with extreme caution if the resorcinol membrane that is forming has modified the permeability of the skin, epidermolysis is present and the skin has been badly injured rough handling (or paste that is too compact) could pull away the skin and sharply increase the risk of post-peel complications in the form of erythema and pigmentary changes. 

At the end of contact time, the paste is removed with a tongue depressor and a dry gauze pad. A small amount of paste can be left on the skin at the end of the peel so that a thin layer of resorcinol remains to give full results. It is not strictly necessary to take the paste olf in the same order it was applied. It can be left to work longer in certain places to increase the strength of the peel locally - for example on the more resistant skin on the forehead. 

It is important not to confuse an allergy with the skin s natural response to the chemical peel applied behind the ear. A highly localized and normal skin reaction to the peel will occur erythema followed by flaking. The appearance of any blistering or pruritus contraindicates any further contact with resorcinol completely and definitively. If a patient is allergic, Unna s paste causes reversible facial eczema, with no cosmetic benefit. 

In the past decades, significant reductions in resorcinol content have been achieved from pure RF resins, to PRF resins in which phenol and resorcinol were used in equal or comparable amounts, to the modern-day commercial resins for glulam and fingerjointing in which the percentage, by mass, of resorcinol on liquid resins is on the order of 15 to 18%. A step forward has also been the development and commercialization of the honeymoon fast-set system [3], either composed of just synthetic PRF resins or of a PRF resin coupled with the use of tannin extracts, which in certain countries are used to obtain PRFs of 8 to 9% resorcinol content without loss of performance and with some other advantages (such as gluing of high moisture content timber). This was a system improvement, not an advance on the basic formulation of PRF resins. 

A second reaction was also carried out as a control. Resorcinol (5 g) was diluted in water (25 ml), and K2CO3 was added as a catalyst (R/Catalyst ratio = 100) to obtain a homogeneous solution. pMDI was then added, the R/pMDI weight ratio was 0.5. The mixture was stirred at ambient temperature and a yellow paste was obtained. A very thin layer of this paste was spread on a glass plate and left at 25°C for 24 h to dry and harden. It was then scraped from the glass and ground for NMR analysis. 

---