Types of Pharmaceutical Formulation

Oral drugs are normally taken as tablets or capsules. The drug (active substance) itself needs to be soluble in aqueous solution at a controlled rate. Such factors as particle size and crystal form can significantly affect dissolution. Fast dissolution is not always ideal. For example, slow dissolution rates can prolong the duration of action. The most important characteristic for oral formulation is that it must be able to overcome the problems associated with oral administration. The most critical problem is rate of drug solubility, i.e., the active ingredient of the drug must be soluble in aqueous solution at a constant rate [39]. The oral formulation is divided in two parts which are Tablet form and Capsule form. 

A tablet is usually a compressed preparation that contains  

The disintegration time can be modified for a rapid effect or for sustained release. Special coatings can make the tablet resistant to the stomach acids such that it only disintegrates in the duodenum, jejimum and colon as a result of enzyme action or alkaline pH. Pills can be coated with sugar, varnish or wax according to the desired taste [40]. 

A capsule is a gelatinous envelope enclosing an active substance. Capsules can be designed to remain intact for some hours after ingestion in order to delay absorption. They may also contain a mixture of slow and fast-release particles to produce rapid and sustained absorption in the same dose [40]. 

Some tablets are designed with an osmotically active core, surrounded by an impermeable membrane with a pore in it. This allows the drug to percolate out from the tablet at a constant rate as the tablet moves through the digestive tract [41]. 

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Diclofenac is an exceedingly potent COX inhibitor slightly more efficacious against COX-2 than COX-1. Its absorption from the gastrointestinal tract varies according to the type of pharmaceutical formulation used. The oral bioavailability is only 30-80% due to a first-pass effect. Diclofenac is rapidly metabolised (hydroxylation and conjugation) and has a plasma half-life of 1.5 h. The metabolites are excreted renally and via the bile. 

The widespread applicability of di-O-methylisosorbide as a medium for chemical reactions or as a solvent for pharmaceutical formulations is well documented. In some cases, an additive synergism of the solvent and the solute was observed. Some typical examples mentioned include that it acts as a solvent for muscle-relaxant drugs, which are otherwise difficultly soluble,226 and is used for topical and other types of pharmaceutical formulations,227,228 transdermal controlled-release films229 and tapes,230 anthelmintic solutions,231 antimycotic emulsions,232 and for the treatment of skin disorders, such as eczema.233... 

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