110 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Extensive toxicological studies confirm the existence of an intact ZPTO molecule. A subacute percutaneous toxicity study on the intact skin of white albino rabbits was performed with a 2% solubilized ZPTO solution, pH 8.8. This 90-day study showed that ,there were no demon- strable systemic effects produced by the repeated application of the prod- uct on skin at greatly exaggerated levels of intended human use (11). Corresponding tests with equivalent levels of sodium pyrithione did pro- duce systemic toxicity. One of the first formulations prepared containing the ZPTO-PEI complex was a clear liquid hair dressing with a ZPTO concentration of 0.5% (Table II). This formulation was based upon an alkoxylated liquid having hydrophylic-hydrophobic groupings. Included in the formulation were natural and synthetic esters, ethoxylated glycerine, and other ingredients that we thought would contribute to a balanced hair dressing. The total nonvolatile solids content was 20%. It was decided to determine clinically if the ZPTO-PEI complex in this product base was an effective treatment for seborrheic dermatitis. Before doing this, the preparation was submitted to a series of pharmacological and toxicological tests to which new products are subjected in order to maintain maximum consumer safety. After the safety of the prepara- tion had been established it was then offered for clinical testing in Europe. Tests were conducted concurrently by dermatologists in Great Britain, France, and Italy. The results of all these tests indicated that the preparation was definitely effective in alleviating dandruff and, in many instances, in controlling even the most severe cases (12). Table II Clear Liquid Hair Dressing Sequence Ingredient Per Cent 95% ethanol 71. 697 Ucon fluid mixture a 13.5 Castor oil 2.0 Diisopropyl adipate 0.5 Liponic EG-I• 2.0 UV light absorber 0.05 Perfume oil 0. 313 Water 7.0 'ZPTO 0.5 PEI 1.0 (Water 1.0 3.7% hydrochloric acid 0.44 (q.s.--pH 8.9) Union Carbide Chemical Co., New York, N.Y. Lipo Chemicals Inc., New York, N.Y.

ZINC PYRITHIONE PREPARATIONS Table III Product Formulations Based upon the ZPTO-PEI Complex 111 Sequence 1 1 1 Sequence 1 1 Sequence 1 1 Clear Shampoo Ingredient Sandopan DTC Acid• Lauric alkanolamide Water ZPTO PEI Water Clear Protein Hair Conditioner Ingredient Water-soluble protein Water ZPTO PEI Water Perfume-hydrotrope 3.7% hydrochloric acid Hair-Thickening Lotion Ingredient Polyvinylpyrrolidone K-30 Water 'ZPTO PEI Water 'Methocel resin b •Water 3.7% hydrochloric acid Per Cent 20.0 3.0 67.0 2.0 4.0 4.0 Per Cent 1.0 97.9 0.2 0.4 0.4 0.1 q.s.--pH 8.8 Per Cent 7.0 40.5 0.5 1.0 1.0 1.0 49.0 q.s.--pH 8.8 Sandoz Chemical Industries, Hanover, N.J. Dow Chemical Co., Midland, Mich. A series of prototype formulations of other hair products was pre- pared (Table III). In many cases the concentration levels of ZPTO are unrealistically high in order to demonstrate the ease of incorporating a large quantity of the complex. The clear shampoo formulation shown in Table III contains Sandopan DTC Acid which is an ethoxylated fatty alcohol material having, in addition, a carboxylic acid function. This acid surfactant is used to neutralize some of the excess PEI that is available when the ZPTO-PEI complex is formed. The pH of the shampoo may be as low as 8.8 without affecting clarity. This shampoo exhibits good foaming properties. In place of the Sandopan DTC Acid other acidic surfactants may be used, such as the phosphoric acid esters of ethoxylated fatty alcohols or