Some drugs may be unsuitable for administration by the oral route. For example protein drugs such as insulin may be denatured by stomach acids; such drugs cannot be made into tablets. Some may be deactivated by the liver (the "first pass effect") making them unsuitable for oral use. However, drugs which can be taken sublingually bypass the liver and are less susceptible to the first pass effect. Bioavailability of some drugs may be low due to poor absorption from the gastric tract; such drugs may need to be given in very high doses or by injection. For drugs that need to have rapid onset, or have severe side effects the oral route may not be suitable. For example Salbutamol can have effects on the heart and circulation if taken orally; these effects are greatly reduced by inhaling smaller doses direct to the required site of action.
Pharmaceutical Process Validation
Tablets can be made in virtually any shape, although requirements of patients and tabletting machines mean that most are round, oval or capsule shaped. More unsusual shapes have been manufactured but patients find these harder to swallow, and they are more vulnerable to chipping or manufacturing problems.
Tablet diameter and shape are determined a combination of a a set of punches and a die. This is called a station of tooling. The thickness is determined by the amount of tablet material and the position of the punches in relation to each other during compression. Once this is done, we can measure the corresponding pressure applied during compression. The shorter the distance between the punches, thickness, the greater the pressure applied during compression, and sometimes the harder the tablet. Tablets need to be hard enough that they don't break up in the bottle, yet friable enough that they disintegrate in the gastric tract.
The tablet is composed of the Active Pharmaceutical Ingredient (that is the active drug) together with various excipients. These are biologically inert ingredients which either enhance the therapeutic effect or are necessary to construct the tablet. The filler or diluent (eg lactose or sorbitol)is a bulking agent, providing a quantity of material which can accurately be formed into a tablet. Binders eg methyl cellulose or gelatin) hold the ingredients together so that they can form a tablet. Lubricants (eg magnesium stearate or polyethylene glycol) are added to reduce the friction between the tablet and the punches and dies so that the tablet compression and ejection processes are smooth. Disintegrants (eg starch or cellulose) are used to promote wetting and swelling of the tablet so that it breaks up in the gastro intestinal tract; this is necessary to ensure dissolution of the API. Superdisintegrants are sometimes used to greatly speed up the disintegration of the tablet. Additional ingredients may also be added such as coloring agents, flavoring agents, and coating agents. Formulations are designed using small quantities in a laboratory machine called a Powder Compaction Simulator. This can prove the manufacturing process and provide information for the regulatory authorities.this website www,tabletsindia,blogspot,com is dedicated for educting pharmaceuticle students
Pharma process validation