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Pellets slow and controlled release coating and equipment (I)

Abstract: This paper introduces the preparation method of slow and controlled release pellets, the preparation of slow and controlled release materials, the coating method of slow and controlled release pellets and its corresponding equipment

key words: pellets; Slow release; Controlled release; Coating; Equipment


enteric dissolution and delayed release drug coating dosage forms are mainly tablet and particle systems. In terms of coating, it is relatively simple for tablets to complete slow and controlled-release coating, but it has the problem of irritation caused by gastric and intestinal metastasis and accidental retention in a certain part. Therefore, in recent years, pellet coating, which regulates drug release, has become increasingly popular in foreign countries

characteristics of slow and controlled release pellets:

(1) it can overcome the performance differences caused by the differences in gastrointestinal metastasis time and irregular gastric emptying

(2) it can be distributed in the whole gastrointestinal tract to absorb drugs, so as to improve the bioavailability

(3) if the drug dose is dispersed in a large number of small pills and some coating fails, the result will not be like the failure of the whole dose of the tablet. Half a year after operation

(4) the drugs were evenly dispersed in each small pill, and the irritation to gastrointestinal mucosa was reduced

I. preparation of slow and controlled release pellets

slow and controlled release pellets can be divided into membrane controlled release pills, skeleton pills and their composite pills according to their prescription composition. According to their forms, different pill preparation methods are adopted

1. Preparation of blank pellet core

blank pellet core is the core required for membrane controlled sustained-release pills, and its components are mainly diluents and binders. Its basic requirements are:

① the prescription ratio should meet the requirements of the process for rapid disintegration after drug release

② sufficient strength: in order not to produce dust during coating operation

③ high sphericity: sufficient sphericity is necessary to ensure the coating process and beauty

the preparation methods of blank pellet core include extrusion rounding method and pot coating machine-made pellet method

a extrusion -- rounding method

① wet material preparation: wet mixing and granulation mechanism is adopted for pellet core auxiliary materials to form wet particles. The auxiliary materials contain binder, so only water is needed

② granulation: the prepared wet material forms a cylindrical strip through the hole after spiral extrusion or rotary extrusion. The particle size of granulation is controlled by the hole size. In terms of rounding, the length and diameter of the strip are roughly the same, so the moisture content of the wet wood must be controlled within a certain range

③ rounding: the strip-shaped particles are placed on the centrifugal turntable, and the high-speed rotation of the turntable makes the material form a circular spiral movement along the wall, and the material keeps tumbling, forming a ball ball with extremely high true sphericity. According to the length of the strip and the characteristics of wet particles, turntables with different surface shapes are selected to achieve the purpose of rolling the strip and preventing slipping

④ drying: it is very important to set the air inlet temperature in stages and control the outward migration speed of water in the core. During the whole drying process, the surface should be prevented from being too wet or cracking

b pot coating mechanism pill method

the traditional pill making method mainly relies on the water chestnut sugar coating pot. This method has simple equipment and low investment cost, but requires high operator experience. Due to its low drying capacity, spray is intermittent, especially the production efficiency of aqueous spray is very low, and the process repeatability is very poor. At the same time, due to the flying dust, it is difficult to pass the verification. The high-efficiency non porous coating machine can be used for pellet core preparation. It has a buried pipe air supply device, and the drying is carried out in a convective manner. Its characteristics are:

① high drying speed and short operation time

② hot air passes through the material layer, with high heat utilization rate and small energy loss

③ closed operation, no dust flying, little cross pollution

④ continuous spray can be operated by program control

⑤ the prepared pellets have higher true sphericity and brittleness than the extrusion and rounding method

⑥ there are no special requirements for pelleting excipients

2. Preparation of matrix sustained-release pills and film containing controlled pellets

matrix sustained-release pills are delayed release pellets prepared by mixing drugs with excipients (blockers). According to the solubility, the excipients selected are non corrosive. Many customers are always careless about matrix materials or corrosive bone frame materials, in which drugs are suspended or dissolved

in terms of pill preparation, the requirements of matrix controlled-release pellets are much higher than those of membrane controlled-release pellets, including:

① meet the disintegration and drug release rate required by the process

② sufficient strength to facilitate further film coating

③ high sphericity

④ in the process of pill making, the measurement and distribution of drugs and blockers must be within the control range

the preparation methods of skeleton sustained-release pills and film containing controlled pellets include extrusion rounding method, centrifugal fluidization pill making method and swirl fluidized bed pill making method. 1 It is best to purchase an experimental machine method of more than 500J

a extrusion rounding method

this method is similar to the operation of membrane controlled slow-release pellets

the following two aspects should be explained:

① there are requirements for blockers, and the roundness of pellets has high requirements for the plasticity of wet materials

② due to the temperature rise caused by extrusion, this method is not suitable for heat sensitive powder

b centrifugation -- fluidization pill making method

centrifugal coating granulation or rotating fluidized bed is applied, the powder and auxiliary materials are put into the bed together, and the binder is sprayed. The mixing -- mothering -- amplification -- pill forming -- drying process is completed in one step


① there are no special requirements for blocker excipients

② the amplification process is completed by spray and the powder mixed with excipients through the spraying mechanism, and the measurement is accurate

③ continuous spray and dusting, short amplification time and high production efficiency

④ the compaction effect of materials in the rotating bed, so it can complete the shot making of low-density materials

⑤ multi-layer sustained-release pellets can be prepared

⑥ there is less thermal medium passing through the slit, which is generally not used for drying operation

⑦ materials with poor fluidity and relatively sticky should not be selected

⑧ the effect of pellets is affected by factors such as spraying speed, rotating speed of rotary table, powder supply speed, blast volume and so on, and the operation is complex

The kugelcoater multifunctional coating machine produced by huttlin company in Germany at the end of the 20th century is another revolutionary achievement of fluidization technology after Wurster system. Its characteristics are:

① the traditional perforated plate is replaced by a turbine driven chassis, and the thermal medium enters tangentially to drive the suspension movement of materials

② the spray gun is placed under the material bed and sprayed at the bottom to shorten the distance between the fog particles and the surface of the material, so that the fog particles are not wasted at all

③ large air flow back blowing and dust cleaning method to ensure that the dust floating in the machine can be brought back to the material layer continuously

④ the material is suspended in the bed and is in the state of rotation, so the pills have high true sphericity

⑤ the material forms a regular flow fluidization in the bed, and the drug content of the prepared skeleton sustained-release pellets is uniform

⑥ convection drying with large air volume, therefore, the amplification and pelleting speed by spraying is fast, and the drug content of the prepared pellets is more uniform than that by powder spraying

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