In: Biology
Explain why some drugs that inhibit prokaryotic protein synthesis have a low therapeutic index.
Therapeutic index:
It is the ratio between the drug that becomes toxic for the organism and dosage at which the drug is effective against the pathogen.
Why prokaryotic protein synthesis inhibitor drugs have low therapeutic index?
Eukaryotic mitochondrial ribosomes are similar to prokaryotic ribosomes. The drug used against the protein synthesis of prokaryotes will also have toxic effects on organism to which the drug is administered. Thus these drugs have a low therapeutic index value.
Example: clindamycin – bind to 50S ribosomes and inhibit the activity of peptidyl transferase.
It prevents the tRNA from binding to the acceptor site of ribosome.
Tetracyclin – bind to 30S ribosomes and prevent binding of aminoacyl tRNA to acceptor site on mRNA.
Toxicity – photosensitivity, hypersensitivity reactions.