We know that drug side effects are a thorny issue that must be faced in the application of drugs and need to be taken seriously. However, under-reporting of drug side effects in hospitals is a very common phenomenon. It has been suggested that excessive workload, various organizational activities, pharmacovigilance systems and potential conflicts are the main reasons for underreporting and underreporting of side effects. In addition, another important reason for this phenomenon is that reporting of toxic side effects is not mandatory.

Phenytoin is a very commonly used antiepileptic drug. However, the drug has a narrow therapeutic window, a nonlinear pharmacokinetic profile, and more importantly, unpredictable drug side effects often occur even when the drug is applied in regular doses. Despite this, the necessary TDM for phenytoin is rarely performed under current medical conditions.

A 52-year-old male was diagnosed with “late onset epilepsy”and was prescribed 200 mg phenytoin twice daily. He had a focal seizure with impaired awareness and was on regular medication. 'e patient was not advised to undergo TDM. After one month of treatment, he could not walk and had frequent falls. He also had an attack of seizure despite being on phenytoin. 'e patient was well-oriented to time, place, and person. Examination of cranial nerves turned out to be normal. Examination of the cerebellum revealed impaired 7nger nose test and dysdiadochokinesia, and heel-to-leg maneuver was also impaired. Romberg’s test also turned out to be positive.

TDM consultation was sought, and as per the advice of the toxicologist, It was slightly above the therapeutic range (30.5 mcg/ml). Normal phenytoin levels in blood range from 10 to 25 mcg/ml. 'en, phenytoin was tapered to 100 mg BD and stopped completely in 3 weeks, after which there was a gradual improvement in ataxia. 'e patient was then switched over to valproate 200 mg twice daily. After three weeks, the patient started walking normally and had no further seizures after discontinuing phenytoin. 'e Naranjo scale was applied, and a score of 7 was obtained, suggesting probable ADR.

This case demonstrates that when developing a treatment plan for a patient with epilepsy, it is more important for physicians to base their design on the data from the TDM rather than solely on the patient's clinical presentation.

The fully automated chemiluminescent drug concentration detection solution from Diagreat has significant advantages in TDM.