Oral alitretinoin: a review of the clinical pharmacokinetics and pharmacodynamics.

Alitretinoin is an endogenous retinoid related to vitamin A. Studies have shown that oral alitretinoin is effective and well tolerated in the treatment of severe chronic hand eczema. This review summarizes the clinical pharmacokinetic and pharmacodynamic data from a number of studies involving alitretinoin. These include the effect of food on the pharmacokinetics of alitretinoin, interactions between alitretinoin and ketoconazole, simvastatin or cyclosporin A, the effect of alitretinoin on the pharmacokinetics of a combined oral contraceptive, alitretinoin in seminal fluid after repeated dosing, and the pharmacokinetics of alitretinoin and its metabolites in a clinical setting.

Influence of alitretinoin on the pharmacokinetics of the oral contraceptive ethinyl estradiol/norgestimate.

BACKGROUND: Alitretinoin (9-cis retinoic acid) is currently registered in many European countries and in Canada as the only licensed treatment for severe chronic hand eczema unresponsive to potent topical corticosteroids. Alitretinoin, like all retinoids, is teratogenic, and women of child-bearing potential must strictly adhere to pregnancy-prevention measures. AIM: To investigate the influence of alitretinoin on the pharmacokinetics (PK) of ethinyl estradiol/norgestimate (Ortho Tri-Cyclen 28(®)), a commonly prescribed combination oral contraceptive. METHODS: In total, 16 healthy premenopausal women received three consecutive cycles of the triphasic contraceptive ethinyl estradiol/norgestimate together with concomitant oral alitretinoin 40 mg once daily during cycle 2. Steady-state PK (noncompartmental analysis) of ethinyl estradiol, 17-deacetyl norgestimate, alitretinoin and its main metabolite 4-oxo-alitretinoin were assessed alone and in combination. RESULTS: The PK profiles of ethinyl estradiol and 17-deacetyl norgestimate were similar when contraceptives were given alone or with alitretinoin, and the area under the plasma concentration vs. time curve and the maximum concentration met the conventional criteria for PK equivalence. Similarly, the influence of ethinyl estradiol/norgestimate on systemic exposure to alitretinoin and 4-oxo-alitretinoin was not clinically relevant. Alitretinoin was well tolerated when given either alone or with ethinyl estradiol/norgestimate. CONCLUSIONS: There was no clinically relevant influence of alitretinoin on the PK of ethinyl estradiol/norgestimate, and no influence of ethinyl estradiol/norgestimate on systemic exposure to alitretinoin and 4-oxo-alitretinoin. Consequently, oral contraception with ethinyl estradiol/norgestimate is an appropriate primary method of birth control during alitretinoin treatment for women of childbearing potential.

Pharmacokinetics of norelgestromin and ethinyl estradiol from two consecutive contraceptive patches.

The primary objective of this open-label study was to determine the pharmacokinetics of norelgestromin (NGMN) and ethinyl estradiol (EE)following two consecutive applications of a contraceptive patch (ORTHO EVRA/EVRA). Twelve healthy women wore the first patch on their abdomen for 7 days and, after removal at 168 hours (day 7), wore a second patch for 10 days (i.e., 3 days beyond the intended 7-day wear period). Blood samples were collected before and at various times up to 456 hours (day 19) after application of the first patch for analysis of NGMN and EE. Mean serum concentrations of NGMN and EE remained within the reference ranges, 0.6 to 1.2 ng/ml and 25 to 75 pg/ml, respectively, during the entire 7-day wear period after application of the first patch and for 10 days after application of the second patch; reference ranges are based on studies with ORTHO-CYCLEN/ Cilest. No patch detached spontaneously. No subject discontinued or experienced a serious adverse event.

The effect of a single dose of osteoprotegerin in postmenopausal women.

Osteoprotegerin (OPG), a tumor necrosis factor (TNF) receptor family member, is a critical regulator of bone resorption. It is an important inhibitor of the terminal differentiation and activation of osteoclasts. This randomized, double-blind, placebo-controlled, sequential dose escalation study was conducted in postmenopausal women to determine the effect of a single subcutaneous (s.c.) dose of OPG on bone resorption as indicated by the biochemical markers, urinary N-telopeptide (NTX) and deoxypyridinoline (DPD), which are stable collagen degradation products. NTX levels decreased within 12 h after OPG administration. At the highest dose administered (3.0 mg/kg), a mean percent decrease in NTX of approximately 80% was observed 4 days after dosing. Six weeks after dosing a mean decrease of 14% in NTX was observed. The levels of bone-specific alkaline phosphatase (BSAP), a marker of bone formation, did not change for approximately 3 weeks after dosing. Thereafter, a modest decrease, reaching approximately 30% at 6 weeks, was observed in the 3.0-mg/kg dose group. The rapid decrease from baseline in NTX and delayed decrease in BSAP indicated that OPG acted primarily on osteoclasts to decrease bone resorption. OPG injections are well tolerated. This study, for the first time, indicates that a single s.c. injection of OPG is effective in rapidly and profoundly reducing bone turnover for a sustained period and that OPG therefore may be effective in treatment of bone diseases characterized by increased bone resorption such as osteoporosis.

Pharmacokinetics of norelgestromin and ethinyl estradiol delivered by a contraceptive patch (Ortho Evra/Evra) under conditions of heat, humidity, and exercise.

The objectives of this randomized, open-label, three-period, incomplete block design study were to evaluate the pharmacokinetics of norelgestromin (NGMN) and ethinyl estradiol (EE) delivered by the contraceptive patch, Ortho Evra/Evra, and to evaluate patch adhesion under conditions of heat, humidity, and exercise. During each treatment period, 30 healthy women wore Ortho Evra on the abdomen for 7 days under one of six conditions (normal activity, sauna, whirlpool, treadmill, cool water immersion, or a combination of activities). Blood samples were collected before and several times to 240 hours after patch application. Mean serum concentrations of NGMN and EE generally remained within the reference ranges, 0.6 to 1.2 ng/ml and 25 to 75 pg/ml, respectively, during the 7-day wearperiodfor all activities. Only 1 (1.1%) of 87 patches completely detached spontaneously. Peel force measurements were comparable for all activities. Ortho Evra was well tolerated. In conclusion, Ortho Evra delivers efficacious concentrations of NGMN and EE and maintains adhesive reliability through 7 days of wear even under conditions of heat, humidity, and exercise.

Randomized safety studies of intravenous perflubron emulsion. I. Effects on coagulation function in healthy volunteers.

Previous perfluorocarbon (PFC) emulsions have been associated with transient adverse events (i.e., platelet activation, decreased platelet count, febrile responses, changes in hemodynamic function). The Phase I studies described in this report were parallel, randomized, double-blinded, placebo-controlled studies conducted in 48 healthy volunteers (n = 24 per study) with perflubron emulsion (Oxygent; Alliance Pharmaceutical Corp., San Diego, CA). Because of the decreased platelet counts observed with previous PFC emulsions and the intended use of perflubron emulsion in surgical patients, these studies assessed postdosing coagulation responses and hemostasis. PFC pharmacokinetic variables were also evaluated. The primary endpoint for examination of coagulation effects was prospectively defined as bleeding time. Subjects received either saline (3 mL/kg) control, or perflubron emulsion at 1.2 g PFC/kg or 1.8 g PFC/kg, and were evaluated for a 14-day period. No postinfusion changes in bleeding time or differences in ex vivo agonist-induced platelet aggregation were observed. A 17% reduction in platelet count was observed 3 days after dosing in the 1.8-g PFC/kg group; levels recovered to baseline by Day 7. The intravascular half-life of perflubron for the first 24 h was dose dependent: 9.4+/-2.2 h and 6.1+/-1.9 h in the 1.8- and 1.2-g PFC/kg groups, respectively. Results indicate that this perflubron emulsion did not affect coagulation function in healthy volunteers.

Randomized safety studies of intravenous perflubron emulsion. II. Effects on immune function in healthy volunteers.

Particle size distribution is a major determinant of particle clearance by the mononuclear phagocytic system and the potential for concomitant activation of resident macrophages. To test the safety of a second-generation perflubron-based emulsion (60% perfluorocarbon [PFC] wt/vol; Oxygent [Alliance Pharmaceutical Corp., San Diego, CA]) with a small mean particle size, two parallel, randomized, double-blinded, placebo-controlled studies were conducted in 48 healthy volunteers (n = 24 per study). The study described herein focuses on safety concerning immune function. The primary endpoint was defined prospectively as delayed hypersensitivity skin test responses with lymphocyte proliferative responses to mitogenic stimulation providing a secondary measure for changes in cell-mediated immunity. Subjects received either perflubron emulsion IV (1.2 g PFC/kg or 1.8 g PFC/kg) or saline (3 mL/kg) control. Perflubron emulsion had no effect on delayed hypersensitivity skin reactions, lymphocyte proliferative potential, circulating immunoglobulins, complement activation, or plasma levels of the inflammatory cytokines, tumor necrosis factor-alpha, interleukin-1 alpha, and interleukin-1 beta. Perflubron emulsion was generally well tolerated, although there was a dose-dependent increase in minor flu-like symptoms in the perflubron treatment groups at 24 h after dosing. Increased serum levels of interleukin-6 were observed in those subjects exhibiting febrile responses. The clinical safety profile of perflubron emulsion supports its continued investigation as a temporary oxygen carrier in surgical patients to reduce exposure to allogeneic blood transfusion.

Effects of celecoxib, a novel cyclooxygenase-2 inhibitor, on platelet function in healthy adults: a randomized, controlled trial.

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs) nonspecifically inhibit cyclooxygenase-1 (COX-1), an enzyme critical to normal platelet function, and COX-2, which mediates inflammatory response mechanisms. Celecoxib, an antiarthritic agent that inhibits COX-2 but spares COX-1 at therapeutic doses, is expected to have minimal effects on platelet function. A double-blind, randomized, placebo-controlled study of 10 days' duration was conducted in 24 healthy adults to compare the effects on platelet function of a supratherapeutic dose of celecoxib (600 mg bid) with a standard dose of naproxen (500 mg bid), a conventional NSAID. Ex vivo platelet aggregation in response to standard agonists (collagen, arachidonate, or U46619 [a thromboxane A2 receptor agonist]), bleeding time, and serum thromboxane B2 (TxB2) level were measured. Unlike celecoxib or placebo, naproxen produced statistically significant reductions in platelet aggregation and serum TxB2 levels and increased bleeding time. The results indicate that even at supratherapeutic doses, celecoxib will not interfere with normal mechanisms of platelet aggregation and hemostasis, supporting the premise that celecoxib is COX-1 sparing relative to conventional NSAIDs.

Pharmacokinetics of a once-daily oral dose of moxifloxacin (Bay 12-8039), a new enantiomerically pure 8-methoxy quinolone.

The pharmacokinetics, safety, and tolerability of oral moxifloxacin, a new 8-methoxy quinolone, were assessed in a randomized, double-blind, placebo-controlled study in which healthy male and female volunteers received either 400 mg of moxifloxacin once daily (n = 10) or a placebo once daily (n = 5) for 10 days. Plasma moxifloxacin concentrations on days 1 and 10 were measured by high-performance liquid chromatography and fluorometric detection. Standard pharmacokinetic parameters were estimated by noncompartmental methods. Natural logarithmic estimates for each pharmacokinetic variable of each subject were analyzed by a two-way analysis of variance. Hematology, blood chemistry, vital signs, and adverse events were monitored, and electrocardiograms (ECG) were performed. Plasma moxifloxacin concentrations of predicted therapeutic relevance were achieved in this study. For day 1, the mean maximum concentration of drug in serum (C(max)) and the area under the concentration-time curve from 0 to 24 h (AUC(0-24)) were 3. 4 mg/liter and 30.2 mg. h/liter, respectively. Corresponding means on day 10 were 4.5 mg/liter and 48 mg. h/liter, respectively. On day 10, the mean elimination half-life was approximately 12 h. Plasma moxifloxacin concentrations exceeded the MIC for Streptococcus pneumoniae throughout the 24-h dosing period. The day 1 and day 10 mean AUC/MIC ratios were 121 and 192, respectively, and the mean C(max)/MIC ratios were 13 and 18, respectively. Moxifloxacin was well tolerated; no clinically relevant changes in the standard laboratory tests, vital signs, or ECG were observed. Pharmacokinetic parameters demonstrated linearity, and estimates of pharmacokinetic/pharmacodynamic ratios (AUC/MIC and C(max)/MIC) indicate that the regimen of 400-mg once daily should be effective for treating a variety of infections. Moxifloxacin was found to be safe and well tolerated in healthy volunteers when it was given as a single daily 400-mg dose for 10 days.

Pharmacokinetics of intravenous amiodarone in patients with impaired left ventricular function.

To evaluate the potential need for modification of dose regimens of intravenous amiodarone in patients with left ventricular dysfunction, the pharmacokinetics of amiodarone and its active metabolite, desethylamiodarone (DEA), were examined after a single 15-minute intravenous infusion of amiodarone 5 mg/kg. Three parallel groups of otherwise healthy volunteers with normal (n = 12), moderately impaired (ejection fraction > 30 but < or = 45%; n = 6), or severely impaired (ejection fraction < or = 30%; n = 6) left ventricular function were enrolled in the study. Serial blood samples were obtained over a 76-day period for estimation of pharmacokinetic parameters. With the exception of the half-life (t1/2) of DEA, statistical comparisons revealed no significant between-group differences in pharmacokinetic parameters or correlations between pharmacokinetic parameters and ejection fractions. The t1/2 of DEA was increased by approximately 60% in patients with severe left ventricular dysfunction compared with that in patients with moderately impaired and normal left ventricular function. The rate of DEA formation is slow, however, and its concentration relative to amiodarone is low. Therefore, it is unlikely that concentrations of DEA in serum would reach levels that contribute significantly to the pharmacologic activity of amiodarone during short-term (up to 2 weeks) intravenous amiodarone therapy. Single doses of amiodarone were well tolerated. The results of this study suggest that intravenous amiodarone can be used with appropriate observation to control arrhythmias, regardless of the degree of left ventricular dysfunction.

The pharmacokinetic-pharmacodynamic (Digit Symbol Substitution Test) relationship of flumazenil in a midazolam steady-state model in healthy volunteers.

To characterize the plasma concentration-effect relationship of flumazenil in the presence of a predefined midazolam level, a double-blind, placebo-controlled, randomized two-way crossover study was conducted in nine healthy male subjects. After reaching a criterion level of midazolam-induced depression of the Digit Symbol Substitution Test (DSST), volunteers received a dose of flumazenil (1.0 mg) or placebo over 1 minute, with the infusion of midazolam continued. Blood samples were collected, simultaneously with the DSST assessment, at predetermined intervals and were assayed for flumazenil and/or midazolam plasma concentrations. Pharmacokinetic-pharmacodynamic modeling techniques were used to estimate the equilibration rate constant (keo) between plasma concentration and effect for flumazenil; a sigmoidal maximum-effect model was used to relate the DSST score to the flumazenil plasma concentration. Flumazenil exhibited a rapid onset (the half-life of equilibration between drug concentration in the blood and drug effect was 3.3 minutes) and short duration of action (the flumazenil plasma concentration causing half-maximal effect was 7.4 ng/ml, which was reached about 1 hour after dosing). The results of this study also show the competitive nature of flumazenil as a midazolam antagonist.

Efficacy and safety of cetirizine therapy in perennial allergic rhinitis.

A double-blind, placebo-controlled trial was undertaken to assess the safety and efficacy of once daily cetirizine in alleviating the symptoms of perennial allergic rhinitis. Subjects were adults with perennial allergic rhinitis, characterized by nasal congestion, postnasal discharge, sneezing, rhinorrhea, nasal itching, lacrimation, ocular itching, and itching of the roof of the mouth, and a total pretreatment symptom severity score of greater than or equal to 8. Patients were randomized to treatment with 10 mg cetirizine, 20 mg cetirizine, or placebo for 4 weeks. Efficacy was assessed in 215 patients and safety in 216. Cetirizine in once daily dosages of 10 or 20 mg proved to be effective in relieving the overall symptoms of perennial allergic rhinitis and particularly postnasal discharge and sneezing. The 10-mg dose afforded optimal symptomatic relief, and the 20-mg dose provided little or no additional benefit. Cetirizine was well tolerated, and the frequency of somnolence was not significantly greater in patients receiving this drug than in those given placebo.

A phase I clinical trial with gadodiamide injection, a nonionic magnetic resonance imaging enhancement agent.

Twenty adult male volunteers were studied in an unblinded, ascending-dose study to evaluate the safety, tolerance, and pharmacokinetics of intravenously administered nonionic gadodiamide injection. Dosages administered were 0.05, 0.1, 0.2, and 0.3 mmol/kg. Subjects were monitored from 36 hours before, through 72 hours after administration. There were no clinically relevant changes in vital signs or electrocardiograms. No clinically significant changes occurred in blood or urine laboratory parameters, although a tendency for minor, transient elevations in serum iron levels 8 to 48 hours after administration was noted. These changes were not dose-related. Nine of 20 subjects reported at least one adverse event; all events were transient and of mild intensity, the most common being dizziness/lightheadedness and perversion of taste or smell. One subject reported discomfort consisting of mild stinging at the injection site during administration. Gadodiamide was excreted unmetabolized in the urine with greater than 95% recovery at 72 hours after administration. The serum elimination half-life was approximately 70 minutes.

Double-blind comparison of cetirizine and placebo in the treatment of seasonal rhinitis.

The efficacy and safety of cetirizine were evaluated in 419 patients with seasonal allergic rhinitis. Using a 4-way, double-blind randomization schedule, patients were given a 1-week course of once daily cetirizine (5, 10, or 20 mg) or placebo. Patient and physician efficacy ratings corresponded, indicating superiority of cetirizine to placebo (P less than .05) in reducing symptom severity scores for sneezing, rhinorrhea, ocular pruritus, nasal pruritus, watering of the eyes, and redness of the eyes. All cetirizine doses achieved higher efficacy ratings (72.7%, 79.2%, and 75.7%, respectively) than placebo (52.9%; P less than .05) by the physician's global assessment. Cetirizine was well tolerated, with sedation being the most common adverse experience, increasing in frequency at higher doses. A dose-response relationship was evident for selected symptoms, and the once daily 5-mg dose was found to be an effective minimum dose.

Hepatobiliary MR imaging: first human experience with MnDPDP.

The first human MR imaging results for the hepatobiliary contrast agent manganese(II)N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate) (MnDPDP) are reported. MnDPDP is a paramagnetic contrast agent specific for hepatobiliary imaging. An imaging study was performed to investigate the presence of contrast enhancement or facilitated visualization of normal structures. Twelve healthy subjects receiving MnDPDP at doses of 3, 10, or 15 mumol/kg were imaged after injection for approximately 30 minutes at 1-5-minute intervals. Transaxial abdominal images were obtained at 1.5 T in a single breath-hold interval of 21 seconds with use of a spin-echo pulse sequence (repetition time = 150 msec, echo time = 20 msec). Liver parenchyma enhancement was observed 1 minute after injection and persisted for at least 30 minutes. Clearance into the gallbladder was visualized within 15 minutes. Enhancement was dose-dependent; a dose of 10 mumol/kg produced a 75%-100% signal enhancement of the liver at 10 minutes after injection.

Pharmacokinetic and pharmacodynamic comparison of an osmotic release oral metoprolol tablet and the metoprolol conventional tablet.

Four double-blind, Latin-square studies were conducted to compare the pharmacokinetics and pharmacodynamic bioavailability of metoprolol OROS (oral osmotic) and the conventional tablet (CT) of metoprolol. Metoprolol OROS (7/95 mg or 14/190 mg) was administered once daily in doses equivalent to 100 mg of metoprolol CT given once, twice, thrice, and four times a day. In all four studies, lower peak plasma concentrations and longer times to peak were observed after metoprolol OROS than after metoprolol CT, indicating a controlled-release profile for metoprolol OROS. beta-Adrenergic blockade, as measured by reductions in exercise heart rate, was lower after metoprolol OROS than after metoprolol CT, but metoprolol OROS provided a smoother and more sustained beta-blockade. All four doses of metoprolol OROS at steady state produced relative pharmacodynamic bioavailability that ranged from 87% to 104% of that produced by equivalent doses of metoprolol CT.

Safety and tolerability of single intravenous doses of T cell modulatory peptide (TCMP-80) in healthy volunteers.

T Cell Modulatory Peptide (TCMP-80), L-lysine-L-serine, is a synthetic dipeptide structurally related to a selected amino acid sequence in human immunoglobulin G. Based on in vitro and preclinical in vivo testing, TCMP-80 has immunomodulatory properties. This report describes the first administration of TCMP-80 to man in a randomized, double-blind, placebo-controlled, single rising-dose tolerability trial. Healthy male volunteers received TCMP-80 or placebo as a 10-minute intravenous infusion. At weekly intervals, two of four subjects were given TCMP-80; the remaining two received placebo. Each subject could receive only one dose during the study. Dosing started at 0.01 mg/kg and was increased to 0.03, 0.1, 0.3, 1, 3, 6.5, and 10 mg/kg. CBCs, blood chemistries, urinalyses, and lymphocyte subset populations were monitored predose and postdose on Days 1, 5, and 14. Three placebo and three TCMP-80 subjects reported adverse events. Adverse events reported after TCMP-80 administration were mild in nature (headache, dizziness, hematoma at injection site), appeared to be independent of dose, and resolved without medical intervention. No clinically significant alterations in vital signs, physical examination parameters, or clinical laboratory values were observed. Based on the results of this study, TCMP-80 is safe and well-tolerated within the dose range studied when administered as single intravenous infusions. Additionally, this study design represents an approach to assess the safety of an investigational immunomodulatory drug.

Ferrioxamine as a magnetic resonance contrast agent. Preclinical studies and phase I and II human clinical trials.

The preclinical and clinical trial experience with ferrioxamine (S-FDF; Salutar, Inc.) as a contrast agent for magnetic resonance imaging (MRI) is summarized. The results in 44 patients or subjects show that the drug is safe and well tolerated when given intravenously. In certain conditions, early results show that the use of this contrast agent provides more information than can be obtained with MRI alone.

Effect of cetamolol on epinephrine-induced hypokalemia.

The effect of cetamolol (an investigational cardioselective beta blocker with intrinsic sympathomimetic activity) on the hypokalemic response to epinephrine infusions in normal subjects was evaluated and compared with placebo and two other beta-adrenergic blocking drugs. After two daily doses of cetamolol 15 mg, atenolol (a cardioselective beta blocker) 50 mg; a long-acting propranolol preparation (a nonselective beta blocker) 80 mg; or placebo, 12 men (mean age, 26.7 years) were infused with epinephrine. The resulting average plasma epinephrine level was 1123 pg/mL, whereas average baseline serum potassium levels for the four treatment groups ranged from 3.94 to 4.07 mEq/L. Epinephrine-induced hypokalemia occurred in the placebo group (maximum potassium decrease of 1.00 mEq/L) and in the atenolol group (maximum potassium decrease of 0.59 mEq/L); potassium levels did not decrease but rose slightly in subjects receiving cetamolol or propranolol. Subjects treated with placebo or atenolol also demonstrated statistically significant prolongation of the QTc interval (0.039 seconds with placebo; 0.023 seconds with atenolol) and frequently developed T-wave flattening and U-wave appearance. After pretreatment with cetamolol or propranolol, however, the QTc interval was unaffected, T-wave abnormalities did not occur, and U waves appeared only rarely. The results of this study indicate that cetamolol blocks epinephrine-induced hypokalemia and associated electrocardiographic changes.

Pharmacokinetics of leucovorin calcium after intravenous, intramuscular, and oral administration.

The pharmacokinetics of leucovorin was evaluated after intravenous, intramuscular, and oral administration in a randomized crossover study of 37 healthy men. A single 25-mg dose of leucovorin calcium was administered intravenously, intramuscularly, or orally to the subjects. Blood samples were obtained immediately before and at 13 time points up to 24 hours after the leucovorin dose. The three treatment phases were separated by one-week intervals. Bioavailability was assessed by measuring over 24 hours the blood concentrations of total folates, the parent compound 5-formyltetrahydrofolate, and the metabolite 5-methyltetrahydrofolate, using differential microbiologic assays with Lactobacillus casei and Streptococcus faecalis. Both intravenous and intramuscular administration produced rapid increases in serum concentrations of biologically active folates; these rises were sustained over time and were still detectable at 24 hours after drug administration. The bioavailability of intravenous and intramuscular doses was comparable based on area under the serum concentration-time curve, although for intramuscular administration, the peak concentration was lower and the time to peak concentration was longer. The initial rise in serum folate with intravenous and intramuscular dosing represented 5-formyltetrahydrofolate; this fell concomitantly with the appearance of 5-methyltetrahydrofolate. Oral leucovorin was 92% bioavailable compared with intravenous administration and produced a predictably different pattern of circulating folates, 5-methyltetrahydrofolate being the predominant form. Terminal elimination half-life, apparent volume of distribution, and clearance of total folate were not significantly different among the three treatments.(ABSTRACT TRUNCATED AT 250 WORDS)