Incompatibility

If drug is mixed with any other antagonistic substances(drug or excipients or packaging material) there is chance of formation of some undesirable substances which may affect the safety and efficacy of pharmaceutical preparation . This phenomena is known as incompatibility.

Classification: Two types

1) Physicochemical incompatibility 2) Therapeutic incompatibility

Physicochemical Incompatibility Unintentional interactions that occur in vitro between

drugs and other components of medicinal products.

Therapeutic incompatibility Unintentional interactions that occur in vivo after the

administration of medicinal products. This incompatibilities are usually known as drug interaction.

1)Precipitationa) Precipitation of Unionized Acids and Basesb) Precipitation on dilution of solutions which contain

cosolventsc) Precipitation by salting outd) Precipitation by ionic interaction

Types of Physicochemical Incompatibility

2) Formation of complex

3) Effects of excipients on drug stability

4) Eutectic mixture

5) Partitioning of substances between aqueous and oily

phases

6) Adsorption on solid particles

7) Sorption on filters.

Precipitation of Unionized Acids and Bases

Precipitation on dilution of solutions which contain cosolvents

Diazepam + Ethanol + Gums or Sugar

Precipitation by salting out

NaCl + Benzoic Acid

Precipitation by ionic interaction

Promethazin HCl+ Thiopentone Na

Formation of complex

Tetracyclin Derivatives+ Caicium, Magnesium

Effects of excipients on drug stability Na metabisulfite + Cisplatin

Eutectic mixture

Ibuprofen + Stearic acid, Stearyl alcohol, Magnesium Stearate