1. Hemin J Majeed MSc. Pharmaceutical sciences
Physical Pharmacy
Lab 2 - Solubilization by complex formation
Hemin J Majeed
MSc. Pharmaceutical sciences

2. Complexation is the reversible association between two or more chemical constituents(ligand and substrate).
In such complexing system equilibrium exist between free and complex drug. Such equilibrium is usually easily reversible.
Complexation relies on relatively weak forces such as Van der Waals forces, hydrogen bonding, coordination and hydrophobic interactions.
Inclusion compound, metal and organic complexation are main types of this technique.

3. The formation of complexation can alter physiochemical properties of drugs like aqueous solubility, stability and absorption.
This technique can be used to improve pharmacokinetics profile of many drugs.
Inclusion complex
Cyclodextrins (CD) are widely used as solubility enhancer, stabilizer against oxidation, and taste masker.
The process is formed by insertion of nonpolar molecule (guest) into the cavity of anther molecule (host) which has hydrophilic exterior and lipophilic core in which appropriately sized organic molecules can formed noncovalent inclusion complex

4. Applications of Cyclodextrins in Drug delivery technology
To improve the physical and chemical properties of drugs
To reduce the side effects of drugs
To enhance the bio-availibility of poorly soluble drug

5. Applications of Cyclodextrins in Food industry
To stabilize flavors and fragrances
To mask undesired tastes in the food and cosmetic industries
Metal ion complex (coordination complex)
Coordination complex is a linkage between transition metal ion, such as zinc, iron and nickel, with one or more counter ions or molecules(called ligand) to produce a complex
The intramolecular interaction of a formed complex depend on the base of Lewis acid-base reaction
Metal ion behaves as Lewis acid, able to accept pair of electron while the ligand is donating pair of electron and become Lewis base
The aqueous silver ion forms a complex ion with ammonia in steps.

6. The formation constant, Kf, is the equilibrium constant for the formation of a complex ion from the aqueous metal ion and the ligands.
The formation constant for Ag(NH3)2+ is:
The large value means that the complex ion is quite stable
When a large amount of NH3 is added to a solution of Ag+, you expect most of the Ag+ ion to react to form the complex ion (large Kf - equil lies far to right).

7. Medical application of coordination complex compounds
Chelation therapy has the large implications in the treatment of metal poising
Deferoxamine is used in the regiment of thalassemia treatment in order to remove chronic iron overload.
One of the treatment line of lead poising is admiration of EDTA
Some of coordination compounds have been applied in the inhibition of growth of tumours

8. Example 1: Iodine is insoluble in water but by complexation with potassium iodide it will be converted to a soluble complex. Experimental work: 1. Weight 0.1 g of iodine and put it in 100 ml water conical flask shake for about 5 minutes and observe the results. 2. Add 1 g of KI to the flask with shaking and observe the results.

9. Elemental iodine dissolves easily in carbone tetrachloride but has poor water solubility.
This issue has been overcome by addition of potassium iodide to the mixture of iodine and water which result in formation free aqueous soluble complex, potassium triiodide
This process is used in production of some types of medicinal (antiseptic) iodine