Tablets - A Solid Unit Dosage form By Mohit Ranglani : Pharmacist

Tablets

Tablets are the most common and convenient dosage form. About 70% of the total medicines are in Tablet form.

Definition of Tablets -

“Tablets are solid, flat or biconvex dishes, unit dosage form, prepared by compressing a drug or a mixture of drugs, with or without diluents.”

Ideal Characteristics of Tablets -

A tablet should have the following ideal properties :-

•Elegant product identity.

•Free of defects like chips, cracks, discoloration, and contamination.

•Sufficient strength (to withstand mechanical shock and agitation during its production, packaging, shipping and dispensing.

•Chemical stability: shelf life

•Physical stability: color, physical integrity like shape etc.

•Release the drug in desired and reproducible manner.

Advantages of Tablet Dosage Forms -

Tablet has a number of advantages,one of the major advantage over capsule, is that tablet is an essentially tamperproof doses form. Other potential advantages of tablets are as followed:

•These are the unit dosage forms which offer the greatest flexibility (with respect to doses) of all oral doses forms.

• Its cost is lowest of all oral dosage forms.

• These are the lightest and most compact of all oral doses forms.

•These are in general the easiest and cheapest to package and ship of all oral dosage forms.

•Product identification is simplest and cheapest, requiring no additional processing steps.

•These may provide the greatest ease of swallowing with least tendency for ''hang-up' above stomach, especially when coated, provided that tablet disintegration is not excessively rapid.

• These are better suited to large scale production than other unit oral forms.

• These have best combined properties of chemical, mechanical, and microbiological stability of all the oral forms.

•Objectionable odor and bitter taste can be masked by coatingtechnique.

•Generally more stable than liquids with longer expiration dates.

•Release rate of the drug from tablet can be tailored to meet pharmacological requirements.

Disadvantages of Tablet Dosage Form -

•Drugs which are destroyed in stomach cannot be prepared in tablets e.g proteins/peptides etc.

•Drugs with bitter taste or odour cannot be formulated in tablets without modification (capsules may be tried)

•Peak and valley effect in plasma time. concentration curve for IR dosage forms.

•The drug with too short half life can not be formulated.

Classification of Tablets (USP)

I. Immediate-release tablet

•Disintegrating tablet (conventional tablet)

•Chewable tablets

•Effervescent tablets

•Sublingual and Buccal tablets

•Lozenges

II. Modified-release tablet

•Extended-release
•Delayed-release

I. Immediate-release tablet -

1.Conventional/Disintegrating tablet :-

It is the most common type of tablets. It is released rapidly after administration. It is intended to be swallowed and undergo disintegration and dissolution in the GIT. The commonly required excipients in these are filler (with low dose drug), disintegrant,binder, glidant, lubricant and antiadherent.

Chewable tablets :-

These tablets are designed for children and elderly people and can be taken without water. The tablet is to be chewed and thus mechanically disintegrated in the mouth, so that no disintegrant is included in its composition. Its important excipients are Flavoring, sweetening and coloring agents. e.g. Chewable Antacid tablets

Effervescent tablets :-

The effervescent tablet is dropped into a glass of water before administration during which Carbon di oxide (CO2) is liberated. It can be taken without water. It facilitates rapid tablet disintegration and drug dissolution. The special packaging is needed to avoid exposure of these tablets to moisture. It is used to obtain rapid drug action e.g Effervescent antacid tablets. The important excipients of these tablets are acid with alkali effervescing compound, flavoring, and coloring agents.

Sublingual and Buccal tablets:-

They are used for drug release in mouth for systemic delivery by avoiding first pass metabolism. Here the drug diffuses into the blood, directly through tissues under the tongue in case of sublingual tablets and through oral mucosa in case of buccal tablets. It facilitates rapid tablet disintegration and drug dissolution. For example, Nitroglycerin sublingual tablet exerts its action within two minutes for rapid relief of "Angina pectoris" attack, because the sublingual area is rich in blood supply. Nitroglycerine suffers from first-pass metabolism if taken orally.

Lozenges :-

These are the tablets which dissolve slowly in the mouth. These are used for local medications in the mouth or throat, e.g. local anesthetics, antiseptics and antibiotics and for systemic drug uptake. In the lozenges no disintegrant is included. Other additives (binder and filler) must have pleasant taste.

II. Modified-Release Tablets

According to the USP/NF the term 'modified release dosage forms' is defined as “one for which the drug release characteristics of time course and/or location are chosen to accomplish therapeutic objectives not offered by the conventional dosage
forms.”

Classification -

Modified release dosage forms may be classified into two types :-

1. Extended-release
2. Delayed release

Extended-release Tablets -

It is defined as the one that allows at least a twofold reduction in the dosing frequency as compared to that of conventional (immediate release) dosage form. For example: controlled release or sustained release tablets

Delayed release Tablets -

“the dosage form that releases a discrete portion or portions of drug at a time (or times) other than promptly after administration.” - USP
Enteric coated tablets are the example of delayed release dosage forms