For the preparation of suppositories, three methods are used:
1. Hand Rolling 2. Compression Molding 3. Fusion Moulding
1. Hand Rolling:
- It is the simplest and oldest method of suppository preparation and may be used when only a few suppositories are to be prepared in a cocoa butter base. It has the advantage of avoiding the necessity of heating the cocoa butter.
- By triturating grated cocoa butter and active ingredients in a mortar, a plastic-like mass is prepared. The mass is formed into a ball in the palm of the hands, then rolled into a uniform cylinder with a large spatula or small flat board on a pill tile. The cylinder is then cut into the appropriate number of pieces which are rolled on one end to produce a conical shape.
- The suppository “pipe” or cylinder tends to crack or hollow in the center, especially when the mass is insufficiently kneaded and softened.
2. Compression Molding:
Compression molding is a method of preparing suppositories from a mixed mass of grated suppository base and medicaments which is forced into a special compression mold using suppository making machines. The suppository base and the other ingredients are combined by thorough mixing. The base softens because of the friction in the process. A mortar and pestle can be used on small scale. On the other hand, large-scale manufacturing involves mechanically operated kneading mixers and a warmed mixing vessel. In the compression machine, the suppository mass is placed into a cylinder which is then closed. After that from one end pressure is applied to release the mass from the other end into the suppository mold or die. When the die is filled with the mass, a movable end plate at the back of the die is removed and when additional pressure is applied to the mass in the cylinder, the formed suppositories are ejected. The endplate is returned, and the process is repeated until all of the suppository mass has been used. When active ingredients are added, it is necessary to omit a portion of the suppository base, based on the density factors of the active ingredients.
3. Fusion Moulding:
The fusion Moulding process involves the following steps:
- Firstly melting the suppository base.
- Then the drug is either dispersed or dissolved in the melted base.
- The mixture is then removed from the heat and poured into a suppository mold.
- The melt is allowed to congeal.
- Now the suppositories are removed from the mould.
Small scale moulds are capable of producing 6 or 12 suppositories in a single operation. Industrial moulds produce thousands of suppositories per hour from a single moulding.
Calibration of the Mould:
The calibration of mold is necessary because the size of the suppositories remains the same from a particular mold but their weight varies because the density of the different types of bases and the medicaments used are different. The first step is to prepare molded suppositories from base material alone. The suppositories are combined and the average weight is recorded. To determine the volume of the mold, the suppositories are melted in a calibrated beaker, and the volume of the melt is determined.
Lubricants used in Mould:
Cocoa butter and glycerol-gelatine bases are required lubrication of molds. This prevents the stacking of bases to the wall of the mold cavity. It is also useful in the easy removal of suppositories from the molds. The lubricants form a film between the wall of the mold cavity and the base of suppositories so, they prevent adhering of bases to the molds. The nature of lubricants should be different from the nature of bases.
Lubricant must be compatible with medicament or adjuncts. In industry, silicone fluid is used as a lubricant. Mould is lubricated using a pad of gauze or muslin or with a small fairly stiff brush. Cotton wool is not used because some fibres adhere to the mould. Excess lubricant can be removed by inverting the mold on a clean white tile.
Following lubricants may be used for the preparation of theobroma oil suppositories.
(a) For cocoa butter bases
Alcohol(90%) – 50 ml
Glycerol – 10 ml
Softsoap 10 gm
(b) For the glycerol-gelatin base
Liquid paraffin or Arachis oil is used as a lubricant
Suppositories must be packed in such a manner that they do not touch each other.
Poorly wrapped and packaged suppositories can lead to staining, breaking, or deformation by melting caused by the adhesion. Suppositories usually are foiled in tin or aluminum, paper, or plastic strips. Overwrapping is done by hand or machine.
Hand-packing yields a non-uniform product so machines are utilized to overcome this problem and machines can wrap 8000 suppositories per hour.
Suppositories should be protected from heat, preferably by storing in the refrigerator.
Polyethylene glycol suppositories and suppositories enclosed in a solid shell are less prone to distortion to a temperature slightly above body temp.
Suppositories should be labelled as:
(a) “STORE IN A COOL PLACE”
(b) “FOR EXTERNAL USE ONLY”
(c) “NOT TO BE TAKEN ORALLY”
Make sure you also check our other amazing Article on : Introduction to Suppositories