Topical systems

Semisolid systems fulfill a special topical need by being able to cling to the surface of application. Such systems are plastic in behavior, which allows semisolids to be mechanically spread uniformly over a surface as an immobile film. For the production of lipid-free ointments, pastes, and creams, several gel-forming polysaccharides are being used. As an emulsifier they can provide a three-dimensional matrix which 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

---

So many materials are used as pharmaceutical necessities and as vehicles in topical systems that they defy... 

Concern for the physical and chemical integrity of topical systems is no different than for other dosage forms. However, there are some unique and germane dimensions to stability associated with semisolid systems. A short list of some of the factors to be evaluated for semisolids is given in Table 12. All factors must be acceptable initially (within prescribed specifications), and all must remain so over the stated lifetime for the product (the product s shelf life). 

Hydrocortisone, Topical Systemic (Cortef, Solu-Cortef) Methylprednisolone (Solu-Medrol)... 

There are three main routes commonly used for administration of drags to the eye topical, systemic and intra-ocular. These are summarized in Figure 12.2. 

Computational methods have had a major impact on almost all areas of science in recent years. The range of applications is now very broad, encompassing molecular biology, materials and surface science, mineralogy, and small molecule chemistry. This article focuses on the application of atomistic computer modeling techniques to materials science. We present a brief survey of the aims and scope of the field and short introduction to the main methodologies. We illustrate the current state of the art of computer modeling studies of materials by recent applications to bulk and surface properties of topical systems. 

The specific type and location of the inflammation determine whether topical, systemic, periocular, or multiple routes of administration are appropriate. 

Severe aspirin Cyclosporine A (topical/ systemic) Surgical excision Cryotherapy Supra tarsal steroid injection Severe Mucolytic (e.g., acetylcystine QID)... 

So many materials are used as pharmaceutical necessities and as vehicles in topical systems that they defy thorough analysis. The pharmacist should nevertheless make some effort to learn of the more common constituents and their principal functions. The compositions of formulations as presented on product labels are the main source of such information. The compositions presented in Table 6 offer a glimpse into the compositional natures of semisolids. 

The ICSs beclomethasone dipropionate, budesonide, flunisolide, fluticasone propionate, and triamcinolone acetonide that are currently available for use are compared and listed in Table 26-12. The ICSs have pharmacokinetic differences that result in different topical/ systemic activity. Most evidence is consistent with log-linear dose-response curves for both indirect and direct responses. The log-linear nature of the dose-response curve for corticosteroid activity raises the issue of how much of a difference in dose (or lung delivery) or potency is detectable. The dose-response curves for the ICSs are relatively flat primarily because all the measures used to assess efficacy (lung function, BHR, symptoms, and as-needed short-acting inhaled /32-agonist use) are downstream events from the anti-inflammatory activity. In general, it takes a fourfold difference in potency or dose to detect clinically significant differences. The table of comparative doses (see Table 26-12) is based on extensive comparative clinical trials. Clinical comparative doses take into consideration potency differences as well as lung delivery differences from the various devices. 

Carotenoids are still highly topical systems for research. Both Sj Sq and S2 Sq electronic relaxation process in carotenoids with 7 to 11 conjugated double bonds have been subjected to very comprehensive study . The lifetime of the S2 state of P-carotene in CS2. measured by a femtosecond absorption method, is found to be 200-250 fs at room temperature . Fs time resolved CARS from p-carotene in solution shows the occurrence of ultra-high frequency (llTHz) beating phenomena and sub-ps vibrational relaxation. The same technique has been used to observe solvent effects on the a C=C stretching mode in the 2 Ag excited state of P-carotene and two derivatives . A similar study has been made with several derivatives of P-carotene. ... 

Topical Systemic Photoirritant contact dermatitis Phototoxicity to a systemic agent Photoallergic contact dermatitis Photoallergy to a systemic agent... 

Synthetic polymers are ubiquitous in the personal care industry. Chapter 6 strives to address this rather broad topic in a straightforward and easily readable fashion. The chapter starts with a brief discussion of how synthetic polymers are made and the nomenclature used to describe some of the more basic structural principles of synthetic polymers. It expands to address many of the synthetic polymers used in personal care formulations based principally on their primary mode of operation, including thickening polymers, fixative polymers, conditioning polymers, and encapsulating polymers, the last subject becoming more important as formulators develop more sophisticated topical systems to deliver active materials. 

Since corticosteroids reduce the immunological defences of the body to most types of infection, their use in the eye should be monitored carefully. The specific type of ocular disease and its response to steroid therapy may determine whether to use topical, systemic and/or local injections. Systemic side effects do not generally occur with limited topical administration. 

---