Page 191

Chapter 109

Doylepopped a blister pack of medication and held up something small and white.

‘A standard paracetamol tablet,’ she said. ‘This is nothing more than compressed powder. It’s a hard, smooth-coated pill.’

She opened another blister pack. This time she held up something blue and white, about the same size as a jellybean.

‘Paracetamol again,’ she said. ‘This time it’s loose powder in a hard-shelled capsule. The outside consists of two halves. The blue half fits inside the white to form a closed casing. They can be filled with anything unpalatable. Some are designed to contain liquids. Now, what these both have in common is they are immediate-release medications. It means they dissolve in the stomach within minutes of being swallowed. This is a safe and reliable way of getting medication directly where it needs to be. Everyone in this room will have taken immediate-release medication.’

Doyle pointed at the stomach on her diagram.

‘However,’ she continued, ‘it isn’t always advantageous to have medication dissolve in the stomach. It might cause nausea, for example, or, as the small intestine is the optimal part of the body for nutrient absorption, it might be preferable for the tablet to bypass the stomach altogether. And for this we have the modified-release drug delivery systems I mentioned earlier. Is everyone still with me?’

Nods all round. Bradshaw did so without looking up from her laptop. She was typing furiously. Poe assumed she was still researching what Doyle had told them in the car.

‘There are many variants of modified-release drug delivery systems. For example, with painkilling opiates it is preferable to use a sustained-release variant. That way the patient gets the dose spread out over the course of a day, rather than in one big hit. There arepulse-release delivery systems that allow different medications to dissolve at different times. This might be useful in complex treatments where the success of one medication is dependent on another already being in the body.’

‘This sounds complicated,’ Flynn said.

‘It does, but it’s not,’ Doyle replied. ‘These tablets have been around for years. But we’re not interested in sustained-release or pulse-release drugs, we’re interested indelayed-release.’

‘Delayed?’

Doyle nodded. ‘These are drugs that are designed to target specific parts of the body, or maybe to work only when blood sugar levels are at a specified level.’

‘How do these work?’ Flynn asked.

‘Science is moving forwards all the time, but currently, the active ingredient – say paracetamol – is coated in a barrier. Natural or synthetic polymers usually. Sometimes chitin, although, like I said, this is a field in constant development. Anyway, when the barrier dissolves, the drug, or in your case, poison, is released. Until then it is completely contained. And the beauty of this system is that the rate the barrier dissolves can be set for however long you want. There is no medical reason to have a barrier that lasts more than twenty-four hours, but there is no scientific reason why it couldn’t last longer. Theoretically, the barrier could last forever.’

‘Like when drug mules swallow condoms full of cocaine then?’ Flynn said.

‘Same theory,’ Doyle said. ‘Obviously, a condom that dissolves is, to quote Poe, as much use as mud flaps on a tortoise. Drug runners don’t want cocaine being released into their mules after a set period of time.’

‘My question is this then,’ Flynn said. ‘If our victims did swallow something covered with a barrier that doesn’t dissolve for three weeks, why didn’t they shit it out like a bit of sweetcorn?’

‘Eloquently put, DI Flynn. Howdoesthe Botanist keep his poison in the victim long enough for the barrier to dissolve?’

‘You know, don’t you?’ Mathers said.

Doyle nodded. ‘I have a theory.’