Phenytoin loading dose adults - For Consumers

A drug nomogram developed in , called the Rumack-Matthew nomogram , estimates the risk of toxicity based on the serum concentration of paracetamol at a given number of hours after ingestion. Use of a timed serum paracetamol level plotted on the nomogram appears to be the best marker indicating the potential for liver injury.

Laboratory studies may show evidence of liver necrosis with elevated AST , ALT , bilirubin , and prolonged coagulation times, particularly an elevated prothrombin time. Automated colorimetric techniques , gas chromatography and liquid chromatography are currently in use for the laboratory analysis of the drug in physiological specimens. Pharmacists may provide up to tablets for those with chronic conditions at the pharmacist's discretion.

However, overdose is a relatively minor problem; for example, 0. In contrast, paracetamol is a safe and effective medication that is taken without complications by millions of people. Continuous monitoring of the electrocardiogram and blood pressure is essential. Cardiac resuscitative equipment should be available. The patient should be observed for signs of respiratory depression.

If administration of intravenous Phenytoin Injection BP does not terminate seizures, the use of other measures, including general anaesthesia, should be considered. In a patient having continuous seizure activity, as compared to the more common rapidly recurring seizures, i. The loading dose is then followed by a maintenance dose of mg given orally or intravenously every hours.

In geriatric patients with heart disease, it has been recommended that the drug be given at a rate of 50 mg over minutes. As for adults, however it has been shown that children tend to metabolise phenytoin more rapidly than adults. This should be borne in mind when determining dosage regimens; the use of serum level monitoring being particularly beneficial in such cases.

Determination of phenytoin serum levels is advised when using Phenytoin Injection BP in the management of status epilepticus and in the subsequent establishing of maintenance dosage. In a patient who has not previously received the drug, Phenytoin Injection BP, mg mg ml , may be given intramuscularly at approximately 4 hourly intervals prophylactically during neurosurgery and continued during the postoperative period for hours.

The dosage should then be reduced to a maintenance dose of mg and adjusted according to serum level estimations. When given by intramuscular injection, phenytoin precipitates out at the injection site and is absorbed slowly and erratically. This route is not, therefore, recommended for treating status epilepticus. To avoid drug accumulation resulting from eventual absorption from intramuscular injection sites, it is recommended that for the first week back on oral therapy the dose is reduced to one-half the original dose.

Monitoring of serum concentrations is also recommended. Intramuscular therapy should generally be limited to 1 week. Phenytoin sodium can be useful in cardiac arrhythmias, particularly those due to digitalis. The recommended dosage is one intravenous injection of Phenytoin Injection BP of 3. The solution should be injected slowly, intravenously and at a uniform rate which should not exceed 1ml 50mg per minute 4.

Patients with a known hypersensitivity to phenytoin or its excipients or other hydantoins. Patients with sinus bradycardia, sino-atrial block, second and third degree AV block or Adams-Stokes syndrome.

Intra-arterial administration must be avoided in view of the high pH of the preparation. A meta-analysis of randomised placebo controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour.

The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for Phenytoin. Therefore patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients and caregivers of patients should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge. The response to phenytoin may be significantly altered by the concomitant use of other drugs see 'Interactions with other Medicaments and other forms of Interaction'.

Severe cardiotoxic reactions and fatalities have been reported with arrhythmias including bradycardia, atrial and ventricular depression, and ventricular fibrillation. Severe complications are most commonly encountered in elderly or gravely ill patients. Cardiac adverse events have also been reported in adults and children without underlying cardiac disease or comorbidities and at recommended doses and infusion rates.

Therefore, careful cardiac including respiratory monitoring is needed when administering IV loading doses of phenytoin. Reduction in rate of administration or discontinuation of dosing may be needed. Serum levels of phenytoin sustained above the optimal range may produce encephalopathy, or confusional states delirium, psychosis or encephalopathy , or rarely irreversible cerebellar dysfunction.

Plasma level determinations are recommended at the first signs of acute toxicity. If plasma levels are excessive, then dosage reduction is indicated. Termination is recommended if symptoms persist.

Abrupt withdrawal of phenytoin in epileptic patients may precipitate the possibility of increased seizure frequency, including status epilepticus.

When, in the judgement of the clinician, it is necessary to reduce the dose of phenytoin, discontinuation, or substitution of alternative antiepileptic medication arises this should be done gradually.

However, in the event of an allergic or a hypersensitivity reaction, where rapid substitution of therapy is warranted, the alternative drug should be one not belonging to the hydantoin class of compounds. Phenytoin may precipitate or aggravate absence seizures and myoclonic seizures.

Herbal preparations containing St John's Wort Hypericum perforatum should not be used while taking phenytoin due to the risk of decreased plasma concentrations and reduced clinical effects of phenytoin see Section 4. Subcutaneous or perivascular injection should be avoided because of the highly alkaline nature of the solution. Intramuscular phenytoin administration may cause pain, necrosis, and abscess formation at the injection site see 4.

Posology and method of administration. Soft tissue irritation and inflammation has occurred at the site of injection with and without extravasation of intravenous phenytoin. Such injection may cause soft tissue irritation of the tissues varying from slight tenderness to extensive necrosis, sloughing and in rare instances has led to amputation.

The intramuscular route is not recommended for the treatment of status epilepticus because of slow absorption. Serum levels of phenytoin in the therapeutic range cannot be rapidly achieved by this method. The liver is the principal site of biotransformation of phenytoin; patients with impaired liver function, elderly patients, or those who are gravely ill may show early signs of toxicity.

Reduced maintenance dosage to prevent accumulation and toxicity may therefore be required in patients with impaired liver function. If the undiluted parenteral Phenytoin Sodium Injection is refrigerated or frozen, a precipitate might form: The product is still suitable for use. A faint yellow coloration may develop, however this has no effect on the potency of the solution. The loading dose should be followed by maintenance doses of mg orally or intravenously every hours.

Continuous monitoring of the electrocardiogram and blood pressure is essential. The patient should be observed for signs of respiratory depression. Determination of phenytoin plasma levels is advised when using phenytoin in the management of status epilepticus and in the subsequent establishment of maintenance dosage.

Other measures, including concomitant administration of an intravenous benzodiazepine such as diazepam, or an intravenous short-acting barbiturate, will usually be necessary for rapid control of seizures because of the required slow rate of administration of phenytoin. If administration of parenteral Phenytoin Sodium Injection does not terminate seizures, the use of other anticonvulsants, intravenous barbiturates, general anesthesia and other appropriate measures should be considered.

Simultaneous assay of felbamate plus carbamazepine, phenytoin, and their metabolites by liquid chromatography with mobile phase optimization. Pharmacokinetics of fosfluconazole and fluconazole following multiple intravenous administration of fosfluconazole in healthy male volunteers. Antifungal serum concentration monitoring: Fluoxetine pharmacokinetics in pediatric patients. American College of Chest Physicians evidence-based clinical practice guidelines.

Current Pediatric Diagnosis and Treatment. Eur J Clin Pharmacol. Pharmacokinetics and tolerability of a higher rifampin dose versus the standard dose in pulmonary tuberculosis patients. Determinants of rifampin, isoniazid, pyrazinamide, and ethambutol pharmacokinetics in a cohort of tuberculosis patients. Pharmacokinetics of adjusted-dose lopinavir-ritonavir combined with rifampin in healthy volunteers. Effects consist of the following: Hypertrichosis , Stevens-Johnson syndrome , purple glove syndrome , rash, exfoliative dermatitis, itching , excessive hairiness , and coarsening of facial features can be seen in those taking phenytoin.

Phenytoin is primarily metabolized to its inactive form by the enzyme CYP2C9. Variations within the CYP2C9 gene that result in decreased enzymatic activity have been associated with increased phenytoin concentrations, as well as reports of drug toxicities due to these increased concentrations.

Phenytoin induces metabolizing enzymes in the liver.

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