Factors affecting hardness of coated tablet

Dear all,

After coating, Is there increase in hardness of tablet? if, yes then which are those factors?



My question to you is why should one test hardness of a tablet after coating?
Its a parameter which is checked as inprocess operation during Compression.
Please think it logically.

[quote=DURGA PRASAD]My question to you is why should one test hardness of a tablet after coating?
Its a parameter which is checked as inprocess operation during Compression.
Please think it logically.[/quote]

What if one needs to check whether hardness changes during shelf-life?

you will have a protocol to check during stability.You must look that protocol for that product.

Tests for coated tablets

I. Water vapor permeability

II. Film tensile strength

III. Coated tablet evaluations:

i)Adhesion test with tensile-strength tester: Measures force required toe peel the film from the tablet surface.

ii)Diametral crushing strength of coated tablet: Tablet hardness testers are used. This test gives information on the relative increase in crushing strength provided by the film and the contribution made by changes in the film composition.

iii) Temperature and humidity may cause film defects. Hence studies are to be carried out.

iv) Quantification of film surface roughness, hardness, & colour uniformity. Visual inspection or instruments are used. Resistance of coated tablet on a white sheet of paper. Resisilient films remain intact, & no colour is transferred to the paper; very soft coating are readily “erased” from the tablet surface to the paper.

[b]Tablet quality. As discussed earlier, the tablets must have the proper porosity, surface, hardness, and moisture content. You can’t have consistent coating without consistent tablet quality.

Waiting period. Most tablets cannot be coated immediately after they’ve been compressed. The energy within the tablets is still fairly high. In fact, they are still warm. In addition, tablet hardness changes over 24 to 48 hours. Let the tablets rest at least that long before you coat them.

Batch size. Variation in batch size changes the required pan speed, gun geometry, spray rates, and temperature. The more your batch sizes vary, the more quality issues that will arise in the coating process.

Solution preparation. Again, consistency is the name of the game. Does your company prepare coating solutions the same way, regardless of the batch, the shift, or the operator? Track the solution temperature, mixer speed, and storage time. All are important. Oh, and is the mixing blade correctly installed? Be sure by marking it “top” and “bottom.”

Spray gun calibration. You should calibrate or check the calibration of the guns every time you change products. This means checking the gun’s overall condition and its filter, nozzle alignment, and needle condition.

Gun geometry. Geometry refers to the gun-to-gun alignment, gun-to-tablet bed alignment, and distance from the gun to the end of the pan. Use a ruler to be sure the distances are consistent. Furthermore, make sure all the guns are pointed in exactly the same direction and are maintaining the same spray pattern.

Pan loading. While loading the tablets, look for tablets that are broken, capped, chipped, or covered with black specks. Doing so will help you pinpoint the source of any defects that occur. Do the defects appear during loading, during initial pan rotation, or after preheating? A visual inspection is critical when coating tablets that are friable or that chip or break easily.[/b]