Carrier prodrugs principles

Carrier prodrugs result from a temporary linkage of the active molecule with a transport moiety that is frequently of lipophilic nature. A simple hydrolytic reaction cleaves this transport moiety at the correct moment (e.g. pivampicillin, bacampicillin,). Such prodrugs are, per se, less active than the parent compounds or even inactive. The transport moiety (carrier gronp) is chosen for its non-toxicity and its ability to ensnre the release of the active principle with efficient kinetics. 

The bioavailability of carrier prodrugs is modulated by using a transient transport moiety such a linkage is not implied for bioprecursors, which result from a molecular modification of the active principle itself. 

The catalysis leading to the active principle is hydrolytic (either through general catalysis or through extra-hepatic enzymes) for carrier prodrugs. For bioprecursors, it seems largely restricted to Phase I metabolizing enzymes. 

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