He said average numbers he expected in a living person taking sertraline was 0.03mg/kg.
He said Ms Baden-Clay’s levels were elevated.
Dr Robertson said drug concentrations in the body usually altered after death, a phenomenon known as “post-mortem redistribution”.
He said studies showed sertraline redistribution usually did not change too much after death but tended towards being slightly higher.
He said elevated levels could be caused by the ingestion of a different amount of drug to the recommended therapeutic amount.
“It might be there is an unusual amount of redistribution in this case, some level of contamination may have occurred during the post-mortem,” he said.
Dr Robertson said there were a number of side-effects for sertraline, including common adverse effects such as anxiety, agitation, confusion, thermo-regulation or an elevation of temperature, and even serotonin syndrome or toxicity.
“This is a well described adverse event that involves unusual behaviours,” he said.
He said serotonin effects varied from individual to individual.
Dr Robertson said serotonin syndrome occurred when levels were too high and started to affect other areas of the brain.
“When you get too much of this drug you can get situations again where more profound confusion might exist in a general way, increased agitation, unusual behaviours,” he said.
He said studies showed individuals who were taking “SSRIs” were more likely to experience suicidal ideation.
“The mechanism behind that is simply unclear … it usually happens when someone first starts to take medication or alters medication, those sort of things,” he said.
In cross-examination by Crown prosecutor Todd Fuller QC, Dr Robertson agreed trace levels of serotonin in the stomach may have been transferred there after death.
http://www.couriermail.com.au/news/...-allison-in-2012/story-fnihsrf2-1226974352079
