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Carbamazepine (CB) is a benzodiazepine-type antiepileptic drug that is primarily used to treat partial and generalised tonic-clonic seizures associated with epilepsy. It works by blocking voltage-gated sodium channels, thereby reducing the spread of abnormal neuronal discharges and controlling seizures[1]. It is also used to treat trigeminal neuralgia and sciatica by stabilizing neuronal cell membranes and alleviating symptoms of neuropathic pain [2]. Carbamazepine is also used to treat manic episodes in bipolar disorder. Its mechanism of action primarily involves regulating neurotransmitter release and inhibiting neuronal hyperactivity, thereby exerting antiepileptic, analgesic and antimanic effects.
There are many challenges associated with the clinical application of carbamazepine, primarily in the following areas [3]:
Hematologic abnormalities: It can lead to blood diseases such as agranulocytosis and aplastic anemia.
Hepatotoxicity: It may cause abnormal liver function, as indicated by symptoms such as nausea, vomiting and jaundice.
Heart problems: These may cause arrhythmia, particularly in patients with a history of heart disease or who are taking other drugs that affect the heart.
Hyponatremia: This condition may cause low sodium levels in the blood, leading to symptoms such as headaches, drowsiness and muscle weakness.
Psychiatric symptoms: These may increase the risk of suicidal thoughts or behavior, particularly when the dose is adjusted.
Carbamazepine is metabolized by the cytochrome P450 enzyme system and may interact with other drugs. For instance, it reduces the effectiveness of oral contraceptives and increases the metabolic rate of warfarin, thereby diminishing its anticoagulant properties. Furthermore, carbamazepine induces its own metabolism, resulting in a decrease in blood concentration of the drug.
Pregnant women: Carbamazepine is classified as a Category D drug during pregnancy and may cause congenital malformations in the fetus, such as spina bifida and cardiovascular malformations.
Lactating women: This substance may be excreted in breast milk, so careful consideration of the benefits and risks is required when using it during breastfeeding.
Elderly people: Due to its mild anticholinergic activity, it may increase the risk of delirium, urinary retention, and increased intraocular pressure in elderly people.
Individual differences: Different patients have different metabolic rates, which can lead to variations in blood drug concentrations and efficacy. This requires dose adjustments to be made on an individual basis.
Compliance issues: Patients may stop taking their medication or adjust the dosage themselves due to adverse reactions or dissatisfaction with how effective the drug is. This increases the risk of seizures or the condition recurring.
Therapeutic drug monitoring (TDM) of carbamazepine is of great clinical significance, mainly in the following aspects:
Dose adjustment: Although the blood concentration of carbamazepine is closely related to its efficacy, there is a non-linear relationship between dose and blood concentration. TDM can be used to monitor blood concentrations and help doctors adjust the dose according to individual circumstances, ensuring the drug remains within the therapeutic window and improving seizure control rates.
Individualized treatment: Pharmacokinetic differences can vary greatly between patients. TDM can be used to develop personalized treatment plans based on blood drug concentrations.
Dealing with drug interactions
Toxicity monitoring: Excessively high blood concentrations of carbamazepine can lead to toxic reactions, including ataxia and coma. TDM can help to detect these concentrations in a timely manner, thereby preventing toxic reactions.
Side effect management: By monitoring blood drug concentrations, it is possible to better balance the efficacy and side effects of drugs, reducing adverse reactions caused by drug overdose or underdose.
Combination therapy: Carbamazepine interacts with many other drugs, which can impact its blood concentration. TDM can monitor these changes and help doctors adjust drug doses to avoid reduced efficacy or increased toxicity due to drug interactions.
Monitoring medication adherence: TDM can determine whether patients are taking their medication as prescribed. Persistently low blood drug concentrations may indicate non-adherence, enabling doctors to intervene more effectively.
In summary, carbamazepine therapeutic drug monitoring (TDM) is an important means of achieving personalized treatment, improving efficacy and reducing adverse reactions. It plays an irreplaceable role in clinical practice.
Reference：
1. Semah, F., et al. "Carbamazepine and its epoxide: an open study of efficacy and side effects after carbamazepine dose increment in refractory partial epilepsy." Ther Drug Monit 1994; 16(6): 537-40
2. Krasniqi, S., et al. "Carbamazepine and lamotrigine plasma concentrations in epileptic patients during optimising therapy." Med Arh 2010; 64(2): 80-3.
3. Yeap, L.L., et al. "Slow carbamazepine clearance in a nonadherent Malay woman with epilepsy and thyrotoxicosis." Ther Drug Monit 2014; 36(1): 3-9
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