Edition: BP 2025 (Ph. Eur. 11.6 update)
Compound Calamine Ointment
DEFINITION
Calamine and Coal Tar Ointment contains 12.5% w/w each of Calamine and Zinc Oxide and 2.5% w/w of Strong Coal Tar Solution in a suitable water-emulsifying basis.
Extemporaneous preparation
The following formula and directions apply.
Calamine, finely sifted 125
Zinc Oxide, finely sifted 125
Strong Coal Tar Solution 25
Hydrous Wool Fat 250
White Soft Paraffin 475
Melt together the Hydrous Wool Fat and the White Soft Paraffin. Triturate the Calamine and Zinc Oxide in the melted base and stir gently, when cooled, to about 40°. Gradually incorporate the Strong Coal Tar Solution and stir until cold.
The ointment complies with the requirements stated under Topical Semi-solid Preparations and with the following requirements.
Content of zinc compounds, calculated as ZnO
19.8 to 22.8% w/w.
IDENTIFICATION
The residue obtained in the Assay is yellow when hot and white when cool.
ASSAY
Gently heat 1 g until the basis is completely volatilised or charred. Increase the heat until the carbon is removed and ignite the residue of ZnO until, after further ignition, two successive weighings do not differ by more than 0.2% of the weight of the residue. Each g of residue is equivalent to 0.8034 g of Zn.
STORAGE
Calamine and Coal Tar Ointment should be kept in a container that minimises evaporation losses.
