drug loading

Drug loading tells you how much of a carrier is actually medicine versus how much is just packaging. It is the mass of drug carried, expressed as a fraction or percentage of the total mass of the loaded carrier (drug plus all the lipid, polymer or stabiliser). If a milligram of nanoparticles contains 0.1 milligram of drug, the drug loading is 10 percent.

Loading matters because the carrier material is not free: it adds cost, bulk and a body burden of excipient. A carrier with very low loading may force a patient to receive a large mass of inert material to get a useful dose, which can be impractical for injection volumes or for excipients that are themselves mildly toxic. Higher loading generally means a more efficient, lower-burden product.

Drug loading is closely related to but distinct from encapsulation efficiency. Loading asks what fraction of the final carrier is drug; encapsulation efficiency asks what fraction of the drug you started with actually got trapped. You can have high encapsulation efficiency but still low loading if the carrier itself is heavy, so formulators report both numbers and try to push each as high as the drug and carrier chemistry allow.