Primaquine belongs to 8-Amino Quinoline derivative which is used to treat malaria
Indication of Primaquine:
Radical cure or prevention of relapse in vivax malaria; after termination of chloroquine phosphate suppressive therapy in areas where vivax malaria is endemic .
SAR OF PRIMAQUINE
· Methoxy group at Position 6 is responsible for optimum activity but this group is not essential for antimalarial activity.
· If we replace the methoxy group at position 6 by hydroxyl group.it will show comparable (same) activity. While when ethoxy group is attached it will show low or negligible activity
· If we replace methoxy group by methyl group at position 6 the compound will become inactive
· Additional substitution on the quinoline nucleus tends to decrease both activity and toxicity.
· The reduction of quinoline nucleus ( hetro ring ) at position 1 into 1,2,3,4 tetra hydro derivative (i.e primaquine ) this will show same pharmacological effect but its potency and toxicity will be decreases means require high dose .
· In amino acid side chain, there are two amino group, for optimum activity, the distance between the two nitrogens of amino acid side chain should be 3-6 or 4-6 carbons means if less than 3 carbons, the activity will be decreases or if more than 6 carbons than also decreases.
· The optimal activity is obtained when the alkyl chain contains 4 to 6 carbon atoms. The greatest activity appears to be achieved in alkyl groups containing 5 carbon atoms.
· Any substitution on the quinoline ring will lead to decrease its antimalarial activity.
1. Tatro DS, Borgsdorf LR. A to Z drug facts. Facts & Comparisons; 2003.