This document discusses drug incompatibility, which occurs when a drug is mixed with other substances and undesirable reactions can occur, affecting safety and efficacy. There are two types of incompatibility: physicochemical, which are unintended in vitro interactions between drugs and other product components; and therapeutic, which are unintended in vivo interactions after administration. Specific examples of physicochemical incompatibilities that can occur include precipitation, complex formation, effects of excipients on drug stability, eutectic mixtures, and partitioning between phases.

2. 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

3. 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.

4. 1)Precipitation
a) Precipitation of Unionized Acids and Bases
b) Precipitation on dilution of solutions which contain
cosolvents
c) Precipitation by salting out
d) Precipitation by ionic interaction

5. 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.

7. Precipitation on dilution of solutions
which contain cosolvents
Diazepam + Ethanol + Gums or Sugar

8. Precipitation by salting out
NaCl + Benzoic Acid

9. Precipitation by ionic interaction
Promethazin HCl+ Thiopentone Na

10. Formation of complex
Tetracyclin Derivatives+ Caicium, Magnesium

11. Effects of excipients on drug stability
Na metabisulfite + Cisplatin

12. Eutectic mixture
Ibuprofen + Stearic acid, Stearyl alcohol, Magnesium
Stearate