The relationship between total and free phenytoin levels and drug toxicity was The mean free phenytoin fraction was 0.076 in patients taking phenytoin alone. Because most of the phenytoin in serum is bound to proteins, the level of serum albumin influences the amount of free phenytoin.
I'd like to briefly discuss the difference between free phenytoin, total phenytoin, and clinically why it matters. I've drawn 9 albumin molecules. The relationship between total and free phenytoin levels and drug toxicity was studied in 80 patients.
Twenty-four were taking phenytoin alone. Drug toxicity was. Phenytoin is 90% bound, but only the free fraction circulates through plasma membranes and is biologically active. Because of rapid equilibration between free. Phenytoin, Free and Total. 0090141. Ordering Recommendation.
Preferred test for therapeutic drug management in patients with renal failure or conditions that. Clinical Information. Phenytoin is the drug of choice to treat and prevent tonic-clonic and psychomotor seizures As the blood concentration drops, the rate at which phenytoin is excreted increases. Phenytoin has a volume of distribution of 0.65 L/kg, and is highly protein bound (90%), mostly to albumin.
Therapeutic monitoring of the pharmacologically active (free drug) fraction of protein-bound medications (e.g., phenytoin) represents a major diagnostic. Usually, a total phenytoin test is used to monitor levels. In the blood, phenytoin is highly bound to serum proteins. Only the portion of phenytoin that is unbound or "free" is pharmacologically active. Only unbound or free drug is pharmacologically active. Usually Therefore, monitoring free phenytoin and free valproic acid is recommended in these patients.
Phenytoin would be expected to alter the free drug levels. As such, interactions with other drugs. (drug-drug interactions) or with diseases amoxil suspension 750. renal impairment. Phenytoin, total and free To determine the level of the drug phenytoin in your blood in order to maintain a therapeutic level and to detect potential for toxicity.