Pival toxicity

Figure 8.21 The antiviral agent adefovir dipivoxil, a POM ester, is converted by esterase into its active component, adefovir. Two molecules of formaldehyde and two of pivalic acid are produced for each molecule of drug, the pivalic acid actually being a bigger concern for toxicity than formaldehyde.

For more about the toxicity of pivalic acid, another common prodrug byproduct, see Brass, E.P. Pivalate-generating prodrugs and carnitine homeostasis in man. Pharmacol. Rev. 2002, 54, 589-598. 

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