Mechanism of Action:
Blocks voltage-gated sodium channels
→ stabilizes neuronal membranes and prevents repetitive firing
What are the A/E of phenytoin ?
What is significance of narrow therapeutic index of phenytoin?
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Phenytoin is an antiepileptic medication commonly used to control seizures, particularly in patients with epilepsy.
Adverse effects
• Drowsiness
• Dizziness
• Ataxia (loss of coordination)
• Nystagmus (involuntary eye movements)
• Confusion or cognitive impairment
• Nausea and vomiting
• Gingival hyperplasia (overgrowth of gum tissue)
• Leukopenia (low white blood cell count)
• Thrombocytopenia (low platelet count)
• Aplastic anemia (rare but serious)
• Osteoporosis (long-term use can affect bone density)
• Vitamin D deficiency
• Hypotension (especially with rapid intravenous administration)
• Arrhythmias (such as bradycardia)
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Very well explained
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Great insight 
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Informative👍🏻
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The narrow TI of phenytoin requires regular monitoring of serum levels to ensure that patients remain within the therapeutic range.
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Nice explanation.
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How to prevent the fluctuations in drug concentration ?
What preventive measures can be taken
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Adverse Effects of Phenytoin: Gum hypertrophy, hirsutism, ataxia, nystagmus, sedation, anemia, rash, hepatotoxicity, and teratogenicity.
Significance of Narrow Therapeutic Index: Small changes in dose or blood levels can lead to toxicity or loss of seizure control.
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During pregnancy if phenytoin is given, it cause foetal hydantoin syndrome
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On long term use major ADE shows Gingival hyperplasia ( overgrowth of the gum tissues )
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Among all things, not to forget Fetal Hydantoin Syndrome. Growth stunting, facial dysmorphism, cleft lip/palate, hypoplasia of digits and nails.
#Neonatology
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Adverse effects of phenytoin include gum hypertrophy, hirsutism, ataxia, nystagmus, rash, and megaloblastic anemia.
Its narrow therapeutic index means small dose changes can cause toxicity or therapeutic failure.
Phenytoin has a narrow therapeutic index, meaning the range between its effective dose and toxic dose is very small. This makes it essential to monitor blood levels closely, as even slight changes in dose or metabolism can lead to toxicity or loss of seizure control. Common adverse effects include dose-related symptoms like nystagmus, ataxia, and sedation, while long-term use can cause gingival hyperplasia, hirsutism, peripheral neuropathy, and teratogenicity. Due to these risks, careful dose adjustment and monitoring are crucial in patients taking phenytoin.
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