Isoniazid is a rare overdose that causes
seizures and there is limited evidence to guide treatment. We report a 20-year-old female migrant who presented with recurrent
seizures after ingesting 25 g of
isoniazid. She was treated with
activated charcoal, repeated doses of
midazolam for the
seizures, and given multiple doses of
pyridoxine (14 mg), limited by availability. She was admitted to
intensive care, and 5.5 hours post-ingestion, she was commenced on
continuous veno-venous hemodiafiltration (
CVVHDF). She was extubated after 24 hours and
CVVHDF was ceased 6 hours later (30 hours post-overdose). Her renal function remained normal and her initial
lactate was the highest at 2.3. She made a full recovery. Five plasma samples were collected before, during, and after
CVVHDF, and
isoniazid was quantified with liquid chromatography-tandem mass spectrometry. A pharmacokinetic analysis of time-
isoniazid concentration data was fitted to a two-compartment model with first-order input (with fixed ka ) with the effect of
CVVHDF modeled as a time-dependent covariate. This suggested that there was initially good clearance with
CVVHDF (4 times endogenous clearance), which rapidly declined within hours.