Activated charcoal is commonly used as an absorbant in the management of poisoning. It is a finely powdered material with a huge surface area, which is capable of binding a variety of drugs and chemicals. Charcoal is given orally and passes through the gut, binding with the ingested substance and thereby reducing or preventing systemic exposure. The use of activated charcoal in a particular case will depend on the substance ingested. For a single dose of charcoal to be effective in reducing absorption, the charcoal must be in direct contact with the ingested substance and therefore must be given as soon as possible after ingestion. Repeat dose administration of activated charcoal is appropriate for some poisons and is thought to act by interrupting enterohepatic recycling and/or promoting drug exsorption from the systemic circulation into the gut lumen.

In a recent case report a 9 kg French Bulldog was given charcoal (1 g/kg) after ingestion of a suspected toxic dose of trazodone. She vomited after administration and charcoal was present in the vomit and within a few hours, she had cough and tachypnoea. She was treated with oxygen and antibiotics and discharged after 2 days only to re-present 2 days later due to progressive respiratory difficulty. Chest x-rays revealed evidence of aspiration pneumonia. She had pleural effusion and thoracentesis yielded a large volume of dark red to black fluid which contained free and intracellular black particulate matter consistent with charcoal. On presentation at a referral centre she had mild tachypnoea and tachycardia. Due to presumed charcoal aspiration with suspected lung rupture, the right middle and right caudal lung lobes were surgically removed. Histology revealed abundant black debris consistent with charcoal and severe granulomatous inflammation. Based on the clinical, gross and histological findings, a diagnosis of severe, chronic, locally extensive, aspiration pneumonia and lung rupture with secondary pleuritis and mediastinitis due to charcoal aspiration was made. She was discharged without respiratory difficulties 11 days later.

Activated charcoal is generally well tolerated but aspiration pneumonia is a potential complication of administration, and this can incite extensive, granulomatous inflammation in the respiratory tract, as the charcoal is insoluble and non-absorbable. The risk of aspiration is increased in sedated animals without airway protection and in brachycephalic breeds, as in the case described above.

Reference: Caudill MN, Stilwell JM, Howerth EW, Garner B. Chronic granulomatous pneumonia and lung rupture secondary to aspiration of activated charcoal in a French Bulldog. Vet Clin Pathol. 2019;48(1):67-70.