Phenytoin pharmacokinetics after intravenous administration to patients receiving enteral tube feeding

Randall, Cameron T. C.; Tett, S. E.

doi:10.1007/bf01871260

Cited by 6 publications

(7 citation statements)

References 21 publications

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“…However, low concentrations of the drug have been found after intravenous administration in neurosurgical patients who received long-term enteral feedings. 26,27 The cause appeared to be increased clearance and not decreased bioavailability, as absorption was not an issue.…”

Section: Altered Pharmacokinetics Of Phenytoin In Critically Ill Patimentioning

confidence: 99%

“…14 Reasons may be increased hepatic metabolism due to stress hormones and cytokines, increased clearance due to hypermetabolism or hypercatabolism during head trauma, elevated free phenytoin concentrations, aggressive protein supplementation, and autoinduction of phenytoin. 15,16,27,47 Methods to Account for Altered…”

Section: Altered Pharmacokinetics Of Phenytoin In Critically Ill Patimentioning

confidence: 99%

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Therapeutic Drug Monitoring of Phenytoin in Critically Ill Patients

2008

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Therapeutic drug monitoring of phenytoin is necessary to ensure therapeutic and nontoxic levels. Hypoalbuminemia, renal failure, and interactions with other highly protein-bound drugs (e.g., valproic acid) alter protein binding of phenytoin. When these conditions are present, free serum concentrations, which represent the pharmacologically active entity, cannot be predicted from total serum concentrations. Besides general alterations in drug distribution and elimination, protein binding is often altered in critically ill patients. Case reports describe phenytoin toxicity secondary to inappropriate dosage adjustments based solely on total serum concentrations in patients with hypoalbuminemia. Free drug measurements and theoretical equations to facilitate the interpretation of total phenytoin serum levels have been introduced. However, they are not widely implemented in clinical practice because evidence of improvements in patient outcomes is limited. Knowledge of the pharmacokinetic properties of phenytoin is indispensable for correct interpretation of total serum concentrations when protein binding is altered. Free serum concentrations should be measured, or theoretically calculated if measurements are unavailable, to avoid misinterpretation of total serum levels and consequent inappropriate adjustments in the dosage of phenytoin in critically ill patients.

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Section: Altered Pharmacokinetics Of Phenytoin In Critically Ill Patimentioning

confidence: 99%

Section: Altered Pharmacokinetics Of Phenytoin In Critically Ill Patimentioning

confidence: 99%

Therapeutic Drug Monitoring of Phenytoin in Critically Ill Patients

2008

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“…Randall and Tett studied intravenous phenytoin use in patients receiving long-term enteral feeding and suggested that the low concentrations of phenytoin observed clinically appeared to be due to increased clearance of the drug and not decreased bioavailability. 21 Interactions between several other drugs and enteral formulas have been described. Valli et al reported tube blockage caused by sedimentation from the concurrent administration of enteral feeds with antacids containing aluminium.…”

Section: Compatibility Of Drugs With Enteral Formulasmentioning

confidence: 99%

“…z Administering medications or nutrient solutions can clog tubes, with the incidence varying from 2% to 9%. 1 The preferred method for tube feeding in hospital is a continuous drip over [12][13][14][15][16][17][18][19][20][21][22][23][24] hours, usually by an infusion pump, as it reduces complications such as pulmonary aspiration and diarrhoea. If continuous drip feedings have been well tolerated, then bolus feeds can be used as long as the feeding tube is placed in the stomach -the stomach acts as a reservoir and delivers tolerable amounts of formula to the intestines.…”

Section: Introductionmentioning

confidence: 99%

Guidelines for Drug Administration During Enteral Feeding

Gilbar

Kam

1997

The Australian Journal of Hospital Pharmacy

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“…In the cases, where drug overdose is considered, nonlinear pharmacokinetics can result in particularly prolonged elimination. [20] When hypoxia is present (pa02 < 55mm Hg) it has been shown that the half-life of the marker drug antipyrine is increased from 8.4 to 18.4 hours, which suggests that episodes of hypoxia can delay the elimination of some drugS. [17,18] Some patients will have been receiving one or more drugs prior to their acute cerebral event and indeed they may have been a factor in its causation.…”

Section: Pharmacokinetic Considerationsmentioning

confidence: 99%

Drugs and Brain Death

Kennedy

Kiloh

1996

Drug Safety

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Brain death protocols facilitate early recognition of death in patients on life support systems. When the clinical situation has deteriorated to a level where brain death is to be considered, it is essential that the effects of drugs be excluded. Most centrally acting drugs depress respiration and would be expected to affect apnoea testing of brain stem function. However, the pharmacodynamic and pharmacokinetic properties of drugs are altered when patients are critically ill, so projections made from data derived from less ill patients or normal volunteers are inappropriate. The entry of drugs into the brain is also altered in some disease states, but there are few data relating to the effects of central depressant drugs in the situation of a disrupted blood-brain barrier or brain damage. Drug screens can assist in determining whether drugs are present, but correct interpretation of the results depends on close liaison between the clinical and laboratory staff. It is in the patient's interests to avoid termination of life support if any centrally active drug is present, unless there are other categorical factors consistent with irreversible brain death, such as demonstrated lack of cerebral blood flow.

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Phenytoin pharmacokinetics after intravenous administration to patients receiving enteral tube feeding

Cited by 6 publications

References 21 publications

Therapeutic Drug Monitoring of Phenytoin in Critically Ill Patients

Therapeutic Drug Monitoring of Phenytoin in Critically Ill Patients

Guidelines for Drug Administration During Enteral Feeding

Drugs and Brain Death

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