Colon delivery efficiencies of intestinal pressure-controlled colon delivery capsules prepared by a coating machine...

Large quantities of pressure-controlled colon delivery capsules (PCDCs) were prepared by a Hicoater-mini pharmaceutical coating machine and colon delivery efficiencies were evaluated in man. Caffeine powder as a model drug was suspended with a polyethylene glycol (PEG) 1000 suppository base at 50 degrees C, and was hardened in no. 0- and no. 2-sized capsular shapes. The capsule-shaped suppositories were coated with 5% w/v ethanolic ethylcellulose (7G grade) solution using the coating machine. By increasing the coating weight of ethylcellulose from 28.6 +/- 1.1 mg to 45.3 +/- 0.2 mg, the mean coating thickness of no. 0 PCDCs increased from 56 +/- 1 microm to 64 +/- 1 microm. With no. 2 PCDCs, the mean coating thickness increased from 50 micro +/- 1 microm to 57 +/- 1 microm by increasing the coating weight of ethylcellulose from 8.1 +/- 0.5 mg to 11.2 +/- 0.3 mg. The no. 0 PCDCs, having a mean ethylcellulose coating membrane thicknesses of 56 +/- 1 microm (type 1) and 64 +/- 1 microm (type 2), as well as no. 2 PCDCs, having thicknesses of 50 +/- 1 microm (type 3) and 57 +/- 1 microm (type 4), were used for in-vivo evaluation in man. After oral administration of test preparations containing 75 mg of caffeine, saliva samples were obtained and salivary caffeine levels were measured by an HPLC method. The first appearance time, Ti, of caffeine in the saliva was used as a parameter for the estimation of the release time of caffeine from PCDCs in the gastrointestinal tract. The mean Ti values of no. 0 PCDCs were 3.3 +/- 0.3 h for type- 1 and 5.3 +/- 0.3 h for type-2 preparations while the mean Ti values of no. 2 PCDCs were 4.3 +/- 0.5 h for type 3 and 5.3 +/- 0.3 h for type 4. There were good correlations between ethylcellulose coating membrane thicknesses and in-vivo Ti values. A colon arrival time of 5 h was reported in our subjects by gastrointestinal magnetomarkergraphy. PCDCs having a mean coating thickness of 64 +/- 1 microm for no. 0 capsules and of 57 +/- 1 microm for no. 2 capsules were thought to deliver caffeine to the human colon efficiently.