Toxicity of phenytoin

Consider phenytoin serum levels if a tricyclic antidepressant is added to therapy or if the patient begins to exhibit signs of toxicity. Adequacy of initial dosage patient compliance changes in regimen or physiologic state or confirmation of intoxication.

Because phenytoin is highly protein bound and only unbound drug is capable of crossing the blood-brain barrier to exert its pharmacologic effect unbound free phenytoin levels may be more clinically relevant than total levels to maximize efficacy and minimize toxicity.

Toxicity of phenytoin. Phenytoin toxicity can occur from an increase in the daily dose of phenytoin changes in the formulations or brands as well as changes in the frequency of administration. It can also occur when patients are started on new medications that interact with the metabolism or binding capacity of phenytoin to plasma proteins. Due to its metabolism by CYP450 liver enzymes multiple drug.

Phenytoin PHT sold under the brand name Dilantin among others is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures also known as grand mal seizures and focal seizures but not absence seizures. The intravenous form fosphenytoin is used for status epilepticus that does not improve with benzodiazepines.

It may also be used for certain heart arrhythmias. Phenytoin displays its primary signs of toxicity on the nervous and cardiovascular systems. Overdose on oral phenytoin mainly causes neurotoxicity whereas cardiovascular toxicity is the main side effect of parenteral administration.

The neurotoxic effects are concentration-dependent and can range from mild nystagmus to ataxia slurred speech vomiting lethargy and. Phenytoin is a hydantoin derivative and a non-sedative antiepileptic agent with anticonvulsant activity. Phenytoin potentially acts by promoting sodium efflux from neurons located in the motor cortex reducing post-tetanic potentiation at synapses.

The reduction of potentiation prevents cortical seizure foci spreading to adjacent areas stabilizing the threshold against hyperexcitability. To assess adherence or suspected toxicity or after adjustment of phenytoin dose 25. Target Concentration 10-20 milligrams per litre 12 Some cases of tonic-clonic seizures can be controlled with lower concentrations 12.

The patients clinical status is more important than concentration measurements and this should always be considered when considering dosage adjustment. Digoxin toxicity also known as digoxin poisoning is a type of poisoning that occurs in people who take too much of the medication digoxin or eat plants such as foxglove that contain a similar substance. Symptoms are typically vague.

They may include vomiting loss of appetite confusion blurred vision changes in color perception and decreased energy. Because of the risks of cardiac and local toxicity associated with intravenous phenytoin oral phenytoin should be used whenever possible. In adults a loading dose of 10 to 15 mgkg should be administered slowly.

The rate of intravenous administration should not exceed 50 mg per minute in adults and 1-3 mgkgmin or 50 mg per minute whichever is slower in pediatric patients. Symptoms of phenytoin toxicity include nystagmus diplopia slurred speech ataxia confusion and hyperglycaemia. Cross-sensitivity reported with carbamazepine.

Antiepileptic hypersensitivity syndrome associated with phenytoin. See under Epilepsy for more information. An increased risk of major congenital malformations and.

Drug levels can be monitored to prevent drug toxicity or adverse drug effects. It is frequently administered in conjunction with other anti-epileptic medications such as phenytoin and valproic acid. In seizure control serum trough levels are useful to assess.

Adequacy of initial dosage patient compliance changes in regimen or physiologic state or confirmation of intoxication. -Therapeutic effect without clinical signs of toxicity occurs more often with serum total concentrations between 10 and 20 mcgmL unbound phenytoin concentrations of 1 to 2 mcgmL. In patients with renal or hepatic disease or in those with hypoalbuminemia the monitoring of unbound phenytoin concentrations may be more relevant.

Sertraline potentially increases the risk of toxicity when given with phenytoin. Manufacturer advises monitor concentration and adjust dose. Severe Evidence for interaction.

Phenytoin is predicted to decrease the exposure to sildenafil. Manufacturer advises monitor efficacy. Moderate Evidence for interaction.

Consider phenytoin serum levels if a tricyclic antidepressant is added to therapy or if the patient begins to exhibit signs of toxicity. Lower doses of phenytoin may be required. If phenytoin is added to tricyclic antidepressant therapy monitor for clinical efficacy of the tricyclic agent.

Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression. Because phenytoin is highly protein bound and only unbound drug is capable of crossing the blood-brain barrier to exert its pharmacologic effect unbound free phenytoin levels may be more clinically relevant than total levels to maximize efficacy and minimize toxicity. Dilantin phenytoin is a seizure medication anticonvulsant used to prevent or treat seizures.

Common side effects of Dilantin include dizziness drowsiness difficulty focusing vision unsteady gate tiredness abnormal involuntary movements nausea vomiting constipation abdominal pain and loss of appetite. Consult your doctor before taking Dilantin if pregnant or breastfeeding. Have kidney or liver problems as you may show early signs of toxicity.

DILANTIN may cause liver damage. Have or had porphyria por-FER-ee-ah. DILANTIN has been associated with harmful effects on blood cells.

Have or had diabetes. Your blood sugar level can be altered while taking DILANTIN. If you take DILANTIN during pregnancy your baby is at risk for serious birth defects and bleeding.

Phenytoin 20 Top Signs of toxicity 1. Ataxia - unsteady gait 2. Slurred speech Kidney Killers creatinine over 13 bad kidney CT Contrast Mycin Antibiotics Vancomycin Gentamicin Notes.

Top 5 toxic drug levels Created Date. 4272021 123818 PM. What is the role of lidocaine or phenytoin in tricyclic antidepressant-induced cardiotoxicity.

103109155636502010487050 PubMed 20548984 Yeung A Shanks D Parwana H Gin K. Acute propafenone toxicity after. Because phenytoin is highly protein bound and extensively metabolised by the liver reduced maintenance dosage may be required in patients with impaired liver function to prevent accumulation and toxicity.

Where protein binding is reduced as in uraemia total serum phenytoin levels will be reduced accordingly. However as the pharmacologically active free drug concentration is unlikely to be. Optimum control without clinical signs of toxicity occurs more often with serum levels between 10 and 20 mcgmL although some mild cases of tonic-clonic grand mal epilepsy may be controlled with lower serum levels of phenytoin.

In most patients maintained at a steady dosage stable phenytoin serum levels are achieved. There may be wide interpatient variability in phenytoin serum levels with. N eurological signs of Lithium toxicity range from mild neurological adverse reactions such as fine tremor lightheadedness lack of coordination and weakness.

To moderate manifestations like giddiness apathy drowsiness hyperreflexia muscle twitching ataxia blurred vision tinnitus and slurred speech. And severe manifestations such as clonus confusion seizure coma and death. Phenytoin Phenobarbital Barbiturates Carbamazepine Trimethoprim-sulfamethoxazole TMP-SMZ Zidovudine Maximum acetaminophen dosages.

Historically the maximum daily adult dose of acetaminophen is 4 g with a recommended dosage of 352-650 mg every 4-6 hours or 1 g every 6 hours. In 2012 the FDA suggested but did not mandate a maximum daily dose for adults of 3 g with no. Anticholinergic toxicity is often one component of tricyclic intoxication.

It has a broad differential including infection infarction stroke or intoxication lithium phenytoin anticholinergics organophosphates differential diagnosis back to contents differential diagnosis. Combined anticholinergic plus sodium channel blocker poisoning eg. Lidocaine Xylocaine phenytoin Dilantin tocainide Tonocard mexiletine Mexitil.

In the presence of digitalis toxicity patients frequently require intensive monitoring until therapeutic levels have been restored. Because all digitalis preparations have long serum half-lives stabilization can take several days. A person with vitamin D toxicity who has taken this combination will usually recover within a few days because calcitriol.

Phenobarbital and phenytoin which can treat epilepsy. American College of Clinical Pharmacy.