Drug concentration, neutralizing antibody

Passive immunization has been attempted for treatment of most VHF infections. This approach has often been taken in desperation, owing to the limited availability of effective antiviral drugs. Anecdotal case reports describing miraculous successes are frequently tempered by more systematic studies, where efficacy is less obvious. For all VHF viruses, the benefit of passive immunization seems to be correlated with the concentration of neutralizing antibodies, which are readily induced by some—but not all—of these viruses. 

The curve of therapeutic effect as a function of time may be temporally displaced with respect to the curve of plasma drug concentration over time, requiring the use of indirect pharmaco-kinetic/pharmacodynamic modeling. Other complicating factors may he at play. For example, over time the formation of antibodies to a protein may neutralize the protein or change its pharmacokinetic profile. At times, the blood concentration-effect relationship is so inaccessible for a particular therapeutic... 

---