OPTION 3

SUBLINGUAL / BUCCAL ROUTE

 

•            Blood perfuses oral regions drains directly into the general circulation.

•            Barrier to drag absorption from these routes is epithelium of oral mucosa.

•            Passive diffusion is the major mechanism of absorption of most drugs.

•            In general, sublingual tablets are designed to dissolve slowly to minimize possibility of swallowing the dose.

 

Exceptions include: Nitroglycerin, Isosorbide dinitrate tablets which dissolves within minutes in buccal cavity to provide promote treatment of acute anginal episodes.

 

 

Factors affecting the sublingual absorption:

Lipophilicity of drug:

•            Drug must have slightly higher lipid solubility than that required for GI absorption is necessary for passive permeation.

 

Solubility in salivary secretion:

•            Drug soluble in aqueous buccal fluid

•            pH and pKa of the saliva: pH of the saliva is 6.0, this pH favors the absorption of drugs which remain unionized.

•            The absorption of the drugs through the oral mucosa occurs if the pKa is greater than 2 for an acid and less than 10 for a base.

 

 

Key concept:

 

Drugs given by sublingual route do not go through the liver first.

For this reason, nitroglycerin is given sublingually (or as a tongue spray). It is non-ionic, very lipid soluble, and very potent.

Venous drainage from the mouth is to the superior vena cava and thus avoids the liver.

•            Drugs given by sublingual route do not go through the liver first.

•            For this reason, nitroglycerin is given sublingually (or as a tongue spray).

•            It is non-ionic, very lipid soluble, and very potent.

•            Venous drainage from the mouth is to the superior vena cava and thus avoids the liver.