Chloroquine is given as 600 mg loading dose because:
Oral absorption of CQ is excellent. About 50% gets bound in the plasma. It has high affinity for melanin and nuclear chromatin: gets tightly bound to these tissue constituents and is concentrated in liver, spleen, kidney, lungs (several hundred-fold), skin, leucocytes and some other tissues. Its selective accumulation in retina is responsible for the ocular toxicity seen with prolonged use. ESSENTIALS OF PHARMAXOLOGY page no.822
It is rapidly absoed
It is rapidly metabolized
It has increased tissue binding
It is rapidly eliminated
Chemotherapy