International Numbering System (INS) for Food Additives: 559
Food additives Europe numbers: E559
Functional Category
Adsorbent; suspending agent; tablet and capsule diluent.
Applications in Pharmaceutical Formulation
Kaolin is a naturally occurring mineral used in oral and topical pharmaceutical formulations. In oral medicines, kaolin has been used as a diluent in tablet and capsule formulations; it has also been used as a suspending vehicle. In topical preparations, sterilized kaolin has been used in poultices and as a dusting powder. Therapeutically, kaolin has been used in oral antidiarrheal preparations.(1,2)
Description
Kaolin occurs as a white to grayish-white colored, unctuous powder free from gritty particles. It has a characteristic earthy or claylike taste, and when moistened with water it becomes darker in color and develops a claylike odor.
Stability and Storage Conditions
Kaolin is a stable material. Since it is a naturally occurring material, kaolin is commonly contaminated with microorganisms such as Bacillus anthracis, Clostridium tetani, and Clostridium welchii. However, kaolin may be sterilized by heating at a temperature greater than 1608C for not less than 1 hour. When moistened with water, kaolin darkens and becomes plastic. Kaolin should be stored in a well-closed container in a cool, dry place.
Incompatibilities
The adsorbent properties of kaolin may influence the absorption of other orally administered drugs. Drugs reportedly affected by kaolin include amoxicillin;(3) ampicillin;(3) cimetidine;(4) digoxin;(5) lincomycin; phenytoin;(6) and tetracycline. Warfarin absorption by rat intestine in vitro was reported not to be affected by kaolin.(7) With clindamycin, the rate (but not the amount) of absorption was affected by kaolin.(8)
Safety
Kaolin is used in oral and topical pharmaceutical formulations and is generally regarded as an essentially nontoxic and nonirritant material. Oral doses of about 2–6 g of kaolin every 4 hours have been administered in the treatment of diarrhea.(1,2)