Toxicology Brief: The toxicity of plastic explosives

Reports of dogs ingesting C-4 have come from nine states and, as described here, from as far away as Kandahar, Afghanistan.
Jun 01, 2013

Composition C-4 is a high-velocity military plastic explosive. The explosive material in C-4 is cyclotrimethylenetrinitramine (C3H6N6O6), commonly called cyclonite or RDX (royal demolition explosive). It exists as white crystalline powder or crystals. The additive materials are binder, motor oil, and plasticizer. It also contains 2,3-dimethyl-2,3-dinitrobutane (DMDNB), which functions as a chemical marker for security forces.

Cyclonite explosive has more explosive power than trinitrotoluene (TNT) does and can be mixed with TNT for aerial bombs, mines, and torpedoes. Cyclonite is also used in the manufacture of smokeless powders and occasionally as a rodenticide, particularly rat poison.1 Cases of recreational abuse of C-4 in people have been reported.2


When ingested, cyclonite explosive may cause adverse central nervous system, renal, and gastrointestinal effects.3 Proposed mechanisms of neurologic effects involve alterations of brain cholinesterase activity, decreased monoamine oxidase activity, antagonism of GABA receptors, and down regulation of glutamate signaling pathways.3

A single oral dose of 14 mg/kg of C-4 in an experimental situation was lethal to a dog. The dog developed signs 7.5 hours after exposure and died 18 hours after exposure. Clinical signs included congested mucous membranes, hyperthermia, tachycardia, hyperventilation, intermittent tremors, rigidity, and convulsions. No treatment was provided. It was concluded that the clinical signs of C-4 toxicosis closely resembled those of strychnine poisoning.4

The oral LD50 of cyclonite in rats and mice is highly variable and ranges from 59 to 500 mg/kg. The LD50 of a coarse granular cyclonite is three times higher than that of a fine powder at 100 mg/kg mixed in a solution or slurry.1

Experimental animal studies indicate that cyclonite is absorbed orally but slowly. Based on limited human exposure data, serum cyclonite concentrations appear to correlate with clinical presentation.1

Cyclonite was detected in the serum of a child for more than 120 hours and in the child's stool for 144 hours after ingestion.5 Cyclonite is metabolized by the liver to carbon dioxide, bicarbonate, and formic acid.6 Rat studies indicated that most of a cyclonite dose is excreted in the feces for as long as 21 days after exposure.1 However, studies with radiolabeled RDX in rats suggested that elimination was primarily through exhaled air and urine.3 Information about the half-life of cyclonite is limited. The estimated apparent terminal elimination half-life was reported to be 15.1 hours.5

The most common symptoms in people ingesting C-4 are seizures, spontaneous vomiting, abdominal pain, weakness, dizziness, and headache. Other reported clinical symptoms and laboratory abnormalities included loss of consciousness, renal failure, metabolic acidosis, hypokalemia, and rhabdomyolysis. There are no reports of human fatalities from cyclonite ingestion.1


C-4 ingestion in a military working dog
The ASPCA Animal Poison Control Center (APCC) consulted on 14 calls regarding exposure of dogs to cyclonite plastic explosives between January 2004 and January 2011. These cases were reported from nine states as well as from a military base abroad (see the sidebar "C-4 ingestion in a military working dog"). No deaths were reported in the APCC database, but not all cases were followed up. Dogs involved were typically state police dogs, explosives-detecting dogs, or military working dogs.7

Signs developed in 57% of the cases. Seizures were seen in 87.5% of animals exhibiting clinical signs. Other clinical signs or laboratory abnormalities included vomiting, acidosis, fasciculations or tremors, harsh respiratory sounds and crackles, elevated liver enzyme activities, hyperesthesia, oral ulcers, tachycardia, polydipsia, and polyuria. Hyperthermia, hyperventilation, dyspnea, transient blindness, and injected and pale mucous membranes were also reported.