The tablets under this category are required to be dissolved first in water or other solvents before administration or application. This solution may be for ingestion or parenteral application or
for topical use depending upon type of medicament used.

Effervescent tablets
The oral dosage forms are the most popular way of taking medication despite having some disadvantages like slow absorption and thus onset of action is prolong. This can be overcome by administrating the drug in liquid from but, many APIs have limited level of stability in liquid form. So, effervescent tablets acts as an alternative dosage form.

The tablet that contains acid substances and carbonate or hydrogen carbonate that react rapidly in the presence of water to release carbon dioxide. Sodium bicarbonate, citric acid and tartaric acid are added to the active ingredients to make the tablet effervescent. This facilitates tablet disintegration and drug dissolution; the tablet disintegration should be complete within few minutes.

Advantages of effervescent tablets:
  1. To obtain rapid drug action, for example analgesics and antacids.
  2. To facilitate drug intake, for example vitamins
  • Effervescent tablets often include a flavor and a colorant.c
  • Effervescent tablets are prepared by direct compression or dry granulation.
  • Effervescent tablets should be protected from moisture, so that a special package is needed; each tablet is completely covered with aluminum foil and kept in a water-proof container, often including a desiccant. Effervescent tablets may be packed in blister packs.
To manufacture these tablets, either wet fusion or heat fusion is adopted. The tablets are compressed soft enough to produce an effervescent reaction that is adequately rapid. Water
soluble lubricants are used to prevent an insoluble scum formation on water surface. To add sweetness to the formulation, saccharin is added since sucrose is hygroscopic and add too much of bulk to the tablet. The manufacturing shall be done under controlled climatic condition to avoid effervescent reaction. The packaging is done under 25% RH at 25ÂșC. Hands of the consumers and atmospheric moisture after opening the container can also result in loss of product quality. The most commonly used effervescent tablet today is aspirin tablet.

Read more : Effervescent Tablet Formulation and Manufacture

Hypodermic tablets
These tablets contain one or more readily water soluble ingredients and are intended to be added in water for injection of sterile water to form a clear solution which is to be injected parenterally. It can be used for medicaments whose stability in water is very poor.

Soluble tablets 

Water soluble tablets are intended for application after dissolution in water and contain an active ingredient should be totally soluble in water at used concentrations. All the excipients used to formulate these tablets are required to be completely soluble in water including the glidants, binders, etc. Companies manufacturing these tablets have patented them.