Effects of Manufacturing Conditions on Pharmaceutical Properties of Petrolatum Ointment-Distribution of Hydrocarbon

Petrolatum ointment, which is an oleaginous ointment, is generally produced through manufacturing processes such as melting, mixing, and cooling. In this type of semisolid formulation, the manufacturing conditions of each process are empirically known to affect the quality of the resultant preparation; however, in many cases, the details of the factors are unclear. To clearly investigate the influence of the pharmaceutical properties of petrolatum ointments, we manufactured several ointments while changing the conditions of the mixing and cooling process after melting white petrolatum. As a result, the temperature at the termination was determined to influence the pharmaceutical properties of the final product. To investigate these phenomena, each petrolatum ointment sample was examined via digital microscopy and laser Raman analysis, and the distribution of the liquid-solid parts of samples was investigated. The internal structure of the ointment sample manufactured at a mixing-stop temperature of 40 °C, the needle crystals and the spherical aggregates surrounding them appropriately coexisted, while the structure exhibited a state wherein the two were linked in a semisolid phase. Meanwhile, for the ointment sample manufactured under the lowest mixing-stop temperature of 25 °C, the liquid part and the spherical aggregates were clearly separated, indicating that the liquid part was easily separated from ointments. In addition, the distribution of the hydrocarbons among the samples was measured via GC-MS; no significant difference in chemical structure was observed. In conclusion, the internal structure of the petrolatum ointment was changed by the manufacturing conditions, and this affected the pharmaceutical properties.

[Development of a Breathable Protective Ointment for Moisture-associated Skin Damage]

In this symposium, we present a novel breathable protective ointment (BPO) formulation developed at the University of Shizuoka for the prevention of moisture-associated skin damage (MASD) intended for use in healthcare settings. MASD occurs when moisture is in constant contact with the skin for prolonged periods of time, causing degradation of the skin barrier. Exposure to physical or chemical stimuli in addition to moisture may lead to different types of moisture-associated dermatitis such as incontinence-associated or periwound dermatitis. Another type of moisture-associated dermatitis, diaper dermatitis, is treated with protective ointments such as white petrolatum and zinc ointment. These ointments protect the skin from irritants but also block insensible dermal perspiration, which promotes further skin maceration. Therefore, we have developed a BPO formulation from white petrolatum and calcium carbonate, which serve as a protectant and pore-forming agent, respectively. In vitro water-proof tests confirmed the skin-protective properties of the BPO, and moisture-permeation tests indicated its breathability. Moreover, the BPO protected the skin from irritants without the loss of skin hydration in rats. Our next step involves the trial of BPO in infants with diaper dermatitis. In the future, this BPO could be used as an ointment base for active pharmaceutical ingredients used to prevent MASD.

Evaluation of Moisturizing Effect of Heparinoid Ointment (Hirudoid Soft Ointment) Diluted by White Petrolatum (Propeto)

Steroid ointments are frequently mixed with moisturizer. It was reported that steroid ointments mixed with moisturizer increase permeability. There are only few studies done on the permeability of the moisturizer. We researched moisturizing effect of heparinoid ointment (Hirudoid Soft ointment) diluted with white petrolatum (Propeto) on the dry skin models by measuring water content of stratum. Two to four fold dilution of Hirudoid to white petrolatum resulted in a significant decrease in the moisturizing effect of the active ingredient. There was no significant difference in moisturizing effect between four times diluted mixture and white petrolatum alone. This leads to the conclusion that steroid ointment mixture with moisturizer is frequently used, but we should take more caution regarding the decrease of moisturizing effect.

Enhanced wound healing by topical application of ointment containing a low concentration of povidone-iodine

OBJECTIVE

To investigate the effect of a novel topical wound-healing agent, low-concentration povidone-iodine ointment (LPIO) with a hydrophobic white petrolatum-rich base on skin-wound models in rats and rabbits.

METHOD

The therapeutic efficacy of topically applied LPIO was compared to that of standard-concentration povidone-iodine ointment (SPIO) and non-treatment control, using a full-thickness skin-wound model in 24 hairless rats and a full-thickness skin-defect model in rabbit earlobes. The animals were kept under standardised conditions at the Central Research Laboratory of Maruishi Pharmaceutical Co. Ltd. (Osaka, Japan). Therapeutic efficacy was evaluated based on macroscopic wound-size reduction, as well as histopathological and immuno-histochemical examinations.

RESULTS

LPIO enhanced wound healing in rat full-thickness skin ulcers, reducing wound size and inflammation, when compared with that in SPIO and non-treatment control. LPIO also markedly improved wound healing in rabbit earlobe ulcers by significantly improving re-epithelialisation, compared with that in SPIO.

CONCLUSION

The results of this study suggest that LPIO is a useful topical therapy for ulcerative lesions.

Dermal irritation of petrolatum in rabbits but not in mice, rats or minipigs

Petrolatum is widely used in cosmetics, topical pharmaceuticals and also as a vehicle in dermal toxicity studies. New Zealand white rabbits treated with white petrolatum (vehicle control) in a 2-week dermal irritation study exhibited moderate to severe erythema starting on Day 7 that subsided towards the end of the study. Histological examination of abraded and non-abraded petrolatum-treated skin obtained at termination (Day 15) revealed mild acanthosis, hyperkeratosis, dermal edema with mixed inflammatory cells in the dermis. Macroscopic and microscopic features noted in rabbits were consistent with dermal irritation to petrolatum. Wistar-Han rats, CD1 mice, C57/Bl/6J mice and Göttingen minipigs treated topically with white petrolatum did not exhibit clinical or histologic evidence of dermal irritation. Therapeutic agents developed for topical application are generally tested in rabbits during some point in development. Interpretation of skin irritation data from a single species can impact risk assessment for humans and on product labeling.