The antiepileptic drug, gabapentin, and another structurally related compound, pregabalin, are increasingly employed in the pharmacotherapy of chronic pain states, although their primary mechanism of action remains a topic of active study. A genomic approach to the study of these drugs may elucidate their potentially novel mechanisms. We examined the heritability of sensitivity to analgesia from gabapentin and pregabalin as a precursor to linkage mapping efforts. Accordingly, 11 inbred mouse strains were tested for inhibition of nociception by gabapentin or pregabalin (50-300 mg/kg, i.p.) in two different preclinical assays of inflammatory pain, the formalin test (5% formalin; 20 microl) and zymosan thermal hyperalgesia on the paw-withdrawal test (3 mg/ml zymosan; 20 microl). Significant strain-dependence of drug action was noted in each case, indicating that sensitivity to these analgesics is heritable. Furthermore, the pattern of strain sensitivities to gabapentin and pregabalin were mostly similar, supporting the notion that they act via similar genetic and physiological mechanisms. However, there was virtually no correlation between strain sensitivities to pregabalin inhibition of formalin nociception and zymosan thermal hyperalgesia. In light of previous data from our laboratory and others regarding morphine analgesia, we now establish and empirically demonstrate the general principle that pharmacogenetic mechanisms underlying analgesic sensitivity are specific to the type of pain being inhibited. This has considerable implications for ongoing pharmacogenetic investigations and, more generally, for the choices of preclinical models of pain used in drug development.