Creams drug molecules

Emollients are often added to cream formulations to modify either the characteristics of the pharmaceutical vehicle or the condition of the skin itself to promote penetration of the active ingredient to act either locally or systemically. The stratum corneum, being keratinized tissue, behaves as a semipermeable artificial membrane, and drug molecules can penetrate by passive diffusion. The rate of drug movement depends on the drug concentration in the vehicle, its aqueous solubility, and the oil/ water partition coefficient between the stratum corneum and the product s vehicle. Commonly used emollients include glycerin, mineral oil, petrolatum, isopropyl pal-mitate, and isopropyl myristate. 

Two reformulations of tretinoin include a porous bead (0.01% gel) (microspheres) and liquid polymer (0.025% cream and 0.025% gel). These are less irritating than standard vehicles for tretinoin. In the topical gel formulation containing polyolprepolymer-2, tretinoin penetration was signiflcantly reduced while epidermal deposition was enhanced, compared with a commercially available gel preparation at the same concentration. Polyolprepolymer-2 promotes retention of drug molecules on the skin surface and in the upper layers of the skin. ... 

This molecule occurs widely not only in pharmaceutical products, where it is used for its metal-complex-ing properties in certain creams and as a component of aminophylline, an anti-asthmatic drug, but also in other industrial applications as a stabilizer, solvent, neutralizer, etc. Several occupation-related contact dermatitis cases due to it in the pharmaceutical sector have been described (Hogan 1990 Dias et al. 1995). It may cross-react with piperazine (cf. above). 

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