What is the risk of using multiple doses of activated charcoal in this patient's situation?

The risk of using multiple doses of activated charcoal primarily lies in the potential to lower phenytoin levels. Activated charcoal works by adsorbing various substances in the gastrointestinal tract, which can include not only the intended target, such as salicylates, but also other medications the patient may be taking, like phenytoin.

Phenytoin is a medication used to control seizures, and it has a narrow therapeutic index. Therefore, fluctuations in its serum levels can lead to either subtherapeutic effects or toxicity. If activated charcoal adsorbs phenytoin, it could significantly reduce its levels in the system, potentially leading to inadequate seizure control and increasing the risk of seizures in patients who rely on this medication.

In contrast, while activated charcoal is effective for preventing the absorption of certain substances when administered promptly after ingestion, its repeated use does not enhance the elimination of salicylates directly; rather, it primarily prevents further absorption. Additionally, gastrointestinal irritation can occur with multiple doses, but this is more of a consequence of activation in the gut rather than a direct interaction with existing medications.

Thus, the primary concern in this scenario is that the use of multiple doses of activated charcoal could disrupt the pharmacokinetics