Introduction
Per oral tablets occupy the broadest and the most significant place among all
pharmaceutical dosage forms. Taking one or two tablets a day with a glass of water is the
easiest and the most acceptable way of administration of a drug to a patient.
Tablets are solid dosage forms usually prepared with the aid of suitable pharmaceutical
excipients. They may vary in size, shape, weight, hardness, thickness, disintegration, and
dissolution characteristics and in other aspects, depending on their intended use and
method of manufacture. Most tablets are used in the oral administration of drugs.
excipients. They may vary in size, shape, weight, hardness, thickness, disintegration, and
dissolution characteristics and in other aspects, depending on their intended use and
method of manufacture. Most tablets are used in the oral administration of drugs.
IDEAL CHARACTERISTICS OF TABLETS
- The tablet should include the correct dose of the drug.
- The appearance of the tablet should be elegant and its weight, size and appearance should be consistent.
- The drug should be released from the tablet in a controlled and reproducible way
- The tablet should be biocompatible, i.e. not include excipients, contaminants and microorganisms that could cause harm to patients.
- The tablet should be of sufficient mechanical strength to withstand fracture and erosion during handling.
- The tablet should be chemically, physically and microbiologically stable during the lifetime of the product.
CLASSIFICATION OF TABLETS
Some of the pharmaceutical tablet types based on the way of administration or
presentation to the patient are listed below:
- Simple uncoated tablets
- Coated tablets
- Effervescent tablets
- Buccal and sublingual tablets
- Chewable tablets
- Multilayered tablets
- Sugarcoated tablets
- Fast-disintegrating tablets
- Vaginal tablets
- Osmotic tablets
- Controlled-release tablets
- Multicomponent tablets
1. Simple uncoated tablets:
The simplest form of a pharmaceutical tablet consists of a combination of a drug and some functional excipients compressed directly. This tablet should be formed by compression without difficulty using binders, disintegrants, and lubricants, and when used by a patient, it should disintegrate in the stomach and should of course be bioavailable. Such simple tablets are manufactured by mixing the drug and excipients in a V-shaped mixer and are compressed in a tablet press using dies and punches of suitable size.
2. Film-coated tablets:
A tablet can be coated with a polymer film to provide greater ease of swallowing, protection against light or moisture, protection of the drug from gastric acidity, and modification or control of drug release rate. Identification of a formulation by color or logo is extremely important today not only for patient safety but also because of the problem of counterfeiting. Polymers and processes are
available to achieve all of these properties.
EXCIPIENTS
Tablet formulation design starts with a predetermined value, which is the dose size. The
amount of drug in a tablet can be a limiting step in formulation design. Tablet excipients can
be classified on the basis of their functionality as listed below:
1. Fillers/diluents
2. Binders
3. Disintegrants
4. Lubricants
5. Glidants
6. Buffering agents
7. Sweeteners
8. Wetting agents
9. Coating agents
10. Matrix formers
Fillers/Diluents Used in Tablet Formulations are:
• Lactose (a-lactose monohydrate, anhydrite b-lactose, spray-dried lactose)
• Microcrystalline cellulose (Avicel PH 101, Avicel PH 200, Emcocel)
• Starch (Corn starch, partially hydrolyzed starch)
• Dibasic calcium phosphate (Emcompress, Di-Tab)
• Mannitol (Parteck, Delta M)
• Sorbitol (Neosorb 60)
• Calcium sulfate (Delaflo)
• Compressible sucrose (Di-Pac, Des-tab, Nu-Tab)
Binders used in Tablet Formulation are:
• Polyvinylpyrrolidone (PVP)
• Sodium carboxymethyl cellulose
• HPMC (Low molecular weight, 5 cps)
• Starch paste
• Simple syrup
Lubricants and Glidants used in Tablet Formulations are:
• Magnesium stearate
• Stearic acid
• Sodium stearyl fumarate
• Hydrogenated vegetable oil
• PEG 4000, 6000
• Hexagonal boron nitride
• DL-Leucine
• Sodium lauryl sulfate
• Gliceryl behenate
• Sodium benzoate
• Colloidal silicone dioxide
• Talc
• Starch
• Super disintegrants
• Sodium starch glycolate (Explotab)
• Cross-linked PVP (Polyplasdone XL)
• Cross-linked carboxymethyl cellulose (Ac-Di-Sol)