How and when to monitor a patient treated with low molecular weight heparin. Fosphenytoin and phenytoin adultpediatric inpatient. Ill check a level 23 days after initiation to make sure phenytoin metabolism is not significantly abnormal, and again 5 days after initiation or any dose change to assess the steadystate concentration. Phenytoin blood levels may assist in avoiding therapeutic overshoot of dosing and development of overt clinical toxicity, given saturable metabolism seen in higher phenytoin dose ranges.
Such a combination has been shown to reduce medical errors and speed. Impact of a phenytoin loading dose program in the emergency. We identified no good quality studies of phenytoin used in this situation. Comparing paediatric intravenous phenytoin doses using physiologically based pharmacokinetic pbpk modelling software. Therapeutic drug monitoring of phenytoin by measurement of plasma concentrations is. Some of the factors complicating phenytoin dosing include a narrow therapeutic window, high degree of protein binding, and nonlinear pharmacokinetics. A guide to drug level monitoring ucsf clinical laboratories. Monitoring with serum phenytoin or free phenytoin levels will help with determining if the dose a patient is on is therapeutic, though ultimately, the patients clinical condition is the most important factor to monitor. Crcl 25 mlmin crcl 10 25 mlmin crcl phenytoin cumulation kinetics. An audit tool will be developed to monitor compliance. Twenty of these patients were 65 years of age or older, and 15 had a cardiac history requir ing medication. Phenytoin dosing calculator and analysis globalrph. Phenytoin dosage, adjustment, and monitoring pharmacy joe. These patients also tend to have low serum albumin.
However, serum drug levels should only be taken when there is a clear indication to. The maintenance dose of fosphenytoin required to maintain the therapeutic trough concentration was simulated to be 779. Iv loading doses of phenytoin 18 and 20 mgkg were modelled in children age 210 years. Timedependent decline in serum phenytoin concentration. Due to zero order kinetics, dosage should not be increased by more than 50100mg increments. Guide for drug level monitoring of commonly used medications. To substantially improve the quality of care, the iom has called for computerized physician order entry cpoe coupled with clinical decision support systems dss. Drug monitoring in patients with epilepsy should not be routinely performed unless to assess adherence or suspected toxicity or after adjustment of phenytoin dose 2,5. Phenytoin does not demonstrate a proportional relationship between drug levels and dose. Clinical decision support of therapeutic drug monitoring of phenytoin.
Ordinarily, this drug should not be given im because of the risk of necrosis, abscess formation, and erratic absorption. Phenytoin clearance showed a timedependent increase. If phenytoin level available prior to loading dose, use equation 1. For phenytoinnaive patients, loading doses can be calculated as follows. In general, assuming that the patients seizures can be controlled with monotherapy. Therapeutic drug monitoring tdm is the individualization of drug dosage. Comparing paediatric intravenous phenytoin doses using. Therapeutic drug monitoring can aid dosage adjustment see section 3 for further advice. Continuous cardiac monitoring rate, rhythm, and blood pressure and observation throughout the period when maximum blood phenytoin concentrations occur approximately 10 to 20 minutes after the end of fosphenytoin infusions blood concentration may be obtained 2 hours after iv dose or 4 hours after im dose. The average halflife of phenytoin in adults is about 24 hours, so any level taken within the first 5 days of initiation or dose change should not be considered a steadystate level. Clinical decision support of therapeutic drug monitoring. Phenytoin loading dose software free download phenytoin. Appropriateness of sampling times for therapeutic drug monitoring. The simcyp populationbased adme simulator software allows.
Therapeutic drug monitoring litfl ccc pharmacology. Data collected to ensure the appropriateness of dosing and monitoring included the length of stay, the numbers of serum drug assays ordered 48. Phenytoin loading dose, free phenytoin loading dose software downloads, page 3. It is even included in the medmath module of epocrates software. Phenytoin for neuropathic pain and fibromyalgia in adults. Appropriate therapeutic drug monitoring of phenytoin. Rttoolbox is a software library to support quantitative analysis of treatment. Recent reports by the institute of medicine iom have publicized the risk of medical errors inherent in americas healthcare system 1,2.
Clinical guideline for the use of phenytoin in epilepsy final. After that, ill monitor the phenytoin level weekly while the patient is still in the hospital. Phenytoin dosing guidelines the concentration at steady state can. Therapeutic drug monitoring of phenytoin is carried out to ensure effective and safe levels. Nhs tayside phenytoin prescribing and monitoring guideline. Target concentration 1020 milligrams per litre 1,2. Differential kinetics of phenytoin in elderly patients. Comparing paediatric intravenous phenytoin doses using physiologically based pharmacokinetic pbpk modelling software hannah batchelora, richard appletonb, daniel b. The loading dose should be followed by maintenance doses by oral or iv administration every 6 to 8 hoursim. Some cases of tonicclonic seizures can be controlled with lower concentrations 1,2.
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