Norbormide (NRB) is a compound that is selectively toxic to rodents of the genus Rattus (including R. norvegicus and R. rattus) but relatively harmless to other animals, including other rodents (Zulian et al., 2007). It was first developed in the 1960s as a non-anticoagulant poison, and sold under the trade names Raticate and Shoxin.

NRB acts as both a vasoconstrictor and calcium channel blocker, simultaneously reducing blood flow and cardiac muscle contraction. Acute symptoms appear within 10 minutes of ingestion of a lethal dose. Rats display increased motor activity and muscle incoordination, followed by weakening of hind extremities, laboured breathing, and convulsive movements. Death occurs within 30 minutes in laboratory rats and within two hours for wild animals (Roszkowski et al., 1965). Because NRB is a rat-specific poison, it poses a lower risk of secondary poisoning of wildlife, domestic and livestock animals, which is considerable with other rodenticides.

One flaw of NRB is that it causes a rapid onset of acute effects, to the extent that rats were observed to develop an evolutionary aversion to the compound, otherwise known as bait shyness or avoidance (Greaves, 1966). Because of bait shyness and the efficacy of other types of rodenticides (anticoagulants) against a wider range of rodents, use of NRB declined significantly in the 1970s.

Landcare Research, a Crown Research Institute in New Zealand, have worked recently to develop an analogue of NRB that delays the onset of acute symptoms, theoretically preventing the development of bait shyness (Rennison et al., 2013). Extensive field and laboratory testing of this compound, named DR8 NRB, is underway in New Zealand, possibly leading to registration of the product. These tests would need to be repeated under Australian conditions before the compound is registered by the APVMA.