Determination of isotretinoin or etretinate and their major metabolites in human blood by reversed-phase high-performance liquid chromatography

Bioanalysis of Endogenous Isotretinoin in Altered and Unaltered Human Plasma by Liquid Chromatography-Tandem Mass Spectrometry Coupled with Electrospray Ionization

Bioanalytical method development and validation of endogenous Isotretinoin with Isotretinoin D5 as internal standard was done as per current regulatory guidelines. The method is simple, rugged and sensitive enough to estimate endogenous Isotretinoin using the chromatography-tandem mass spectrometry technique. An alternative approach has been adopted for quantitative analysis of endogenous Isotretinoin in human plasma. Isotretinoin free matrix (surrogate matrix) was prepared and further used for the development and validation of Isotretinoin. The method was validated in altered and unaltered plasma. The chromatographic optimization was done with column (ACE C18, 100 × 4.6 mm I.D. 5 μm particle size), using a mobile phase containing 1 mM ammonium acetate, pH 3.0 as a solvent A and solvent B (1 mM ammonium acetate (pH 3.0) with acetonitrile in a ratio of 10:90). A flow rate was set at 0.75 mL/min in a binary gradient mode. The analyte was recovered by liquid-liquid extraction method with diethyl ether as an extraction solvent. Multi-reaction monitoring mode in negative polarity was implemented for the quantification of endogenous Isotretinoin in plasma. The calibration curve of Isotretinoin was linear (r2 > 0.9992) over the concentration range of 0.5-1000 ng/mL. The intra-day precision was found in a range of 2.0-3.9% CV for altered samples and 0.9-3.7% CV for unaltered samples. The inter-day precision was found 2.6-6.1% CV for altered samples and 1.3-3.8% CV for unaltered samples. The average recovery of the extraction procedure was found 64.6% for altered samples and 62.2% for unaltered samples.

Non-medication Acquired Sticky Skin: Case Report of Idiopathic Acquired Cutaneous Adherence and Review of Medication-Induced Sticky Skin

Sticky skin is a dermatologic phenomenon in which the skin may cause objects to adhere to it on contact or adhere to itself or both. The entire skin can be affected in patients with sticky skin. Alternatively, just acral sites, such as the hand, can be involved. The acquisition of sticky skin has been described in patients treated with certain medications. These drugs include retinoids, proton pump inhibitors, and antifungals; they also include combination therapy utilizing an antineoplastic agent and an antifungal drug in patients with hormone-resistant prostate cancer.

The pathogenesis of acquired cutaneous adherence in patients with androgen-independent prostate cancer was postulated to be the result of therapy-induced elevation of endogenous retinoids. Retinoids have multiple biological effects on epidermal differentiation that may contribute to the pathogenesis of acquired cutaneous adherence. These include the induction of fine, granular, mucus-like deposits within and between the keratinocytes in the upper stratum spinosum and stratum corneum, modulation of lipid composition in keratinocytes, prevention of cross-linked, cornified envelope formation in keratinocytes by the inhibition of epidermal transglutaminase, and altered and decreased content of keratin within the epidermis. We describe an older man who developed non-medication acquired sticky skin (NoMasts). His acquired cutaneous adherence was considered to be idiopathic. We postulate that aging may be associated with elevated endogenous retinoid levels in older individuals and may have resulted in his sticky skin. Further investigation into these retinoid-induced effects and to what extent they promote acquired cutaneous adherence is still needed.

Phase II study of oral capsular 4-hydroxyphenylretinamide (4-HPR/fenretinide) in pediatric patients with refractory or recurrent neuroblastoma: a report from the Children's Oncology Group

PURPOSE

To determine the response rate to oral capsular fenretinide in children with recurrent or biopsy proven refractory high-risk neuroblastoma.

EXPERIMENTAL DESIGN

Patients received 7 days of fenretinide: 2,475 mg/m(2)/d divided TID (<18 years) or 1,800 mg/m(2)/d divided BID (≥18 years) every 21 days for a maximum of 30 courses. Patients with stable or responding disease after course 30 could request additional compassionate courses. Best response by course 8 was evaluated in stratum 1 (measurable disease on CT/MRI ± bone marrow and/or MIBG avid sites) and stratum 2 (bone marrow and/or MIBG avid sites only).

RESULTS

Sixty-two eligible patients, median age 5 years (range 0.6-19.9), were treated in stratum 1 (n = 38) and stratum 2 (n = 24). One partial response (PR) was seen in stratum 2 (n = 24 evaluable). No responses were seen in stratum 1 (n = 35 evaluable). Prolonged stable disease (SD) was seen in 7 patients in stratum 1 and 6 patients in stratum 2 for 4 to 45+ (median 15) courses. Median time to progression was 40 days (range 17-506) for stratum 1 and 48 days (range 17-892) for stratum 2. Mean 4-HPR steady-state trough plasma concentrations were 7.25 μmol/L (coefficient of variation 40-56%) at day 7 course 1. Toxicities were mild and reversible.

CONCLUSIONS

Although neither stratum met protocol criteria for efficacy, 1 PR + 13 prolonged SD occurred in 14/59 (24%) of evaluable patients. Low bioavailability may have limited fenretinide activity. Novel fenretinide formulations with improved bioavailability are currently in pediatric phase I studies.

HPLC/MS(N) analysis of retinoids

This protocol describes a highly sensitive and selective method to quantify retinoids using normal-phase HPLC with online APCI MS(N). The retinoids are key regulators of gene expression, retinol being oxidized via a retinaldehyde intermediate to retinoic acid (RA) which activates specific nuclear receptors, the signalling of which is turned off by oxidative inactivation of the ligand to 4-oxo-RA and other metabolites. Many of these retinoids are present only transiently at low concentrations in tissues and during analysis are labile to heat, light, and oxygen. HPLC with online APCI MS(N) provides a rapid technique to quantify these retinoids simultaneously. Techniques to extract the retinoids and prevent their degradation are described, with an emphasis on transcriptionally active RA. RA controls patterning of gene expression in the embryo, organizing embryonic morphology in the central nervous system. Similarly, a patterned distribution of RA controls function of the adult CNS, a tissue particularly difficult to analyse for RA because of its high lipid content. To understand how these patterns are organized in the brain and change over time, it is essential to determine the concentration of RA in small areas of tissues, and techniques of exquisite sensitivity are indispensable.

Chemoprevention of 4-NQO-induced oral carcinogenesis by co-administration of all-trans retinoic acid loaded microspheres and celecoxib

All-trans retinoic acid (atRA) is one of the most potential chemopreventive agents for head and neck squamous cell carcinoma (HNSCC). However, the induced metabolism of atRA by cytochrome P450s in the liver limits its clinical applications. To overcome such limitation, we had developed atRA-loaded microspheres designed to release atRA for a long period. Unfortunately, the atRA-loaded microspheres severely induced inflammatory responses: that is, atRA released from the microspheres significantly induced the proliferation of fibroblasts and collagen deposition, thereby causing a permeability barrier for drugs from entering the blood stream. In the present study, the effects of celecoxib as an anti-inflammatory drug are investigated when it is concurrently used with atRA-loaded microspheres to treat 4-NQO-induced oral carcinogenesis. We investigated if it might influence the plasma concentration of atRA and its metabolism by preventing the fibroblast proliferation and collagen deposition, reduce the toxicity level of atRA, and improve the chemopreventive efficacy of atRA-loaded microspheres. The concurrently administered celecoxib prevented inflammatory responses and suppressed the number of fibroblasts and collagen deposition in the fibrous capsules for 14 days. The atRA concentration in plasma was also increased and the metabolism of atRA was significantly decreased within 2 weeks. In the 4-NQO-induced oral carcinogenesis study, the incidence of invasive SCC was above 44% when F344 rats were treated with atRA-loaded microspheres. However, the treatment using atRA-loaded microspheres and celecoxib concurrently could reduce the incidence of invasive SCC up to 28%, and three of 25 rats were found to have no tongue lesions. In conclusion, the concurrent use of celecoxib could maintain the atRA concentration in plasma at a higher level while reducing its metabolism by preventing inflammatory responses, thereby improving their chemopreventive effects against 4-NQO-induced oral carcinogenesis.

Inhibition of tumor growth by biodegradable microspheres containing all-trans-retinoic acid in a human head-and-neck cancer xenograft

Retinoids play essential roles in the regulation of cell differentiation and in the proliferation of various epithelial tissues, and atRA is one such active metabolite of retinoids. However, despite the known functions of atRA, its clinical applications are limited due to the induced metabolism by the specific cytochrome P-450s in the liver. To overcome the limitation, parenteral administration of atRA-loaded biodegradable microspheres, the PDLLA/PLE microspheres containing atRA, was suggested previously. We evaluated chemotherapeutic efficacy of atRA-loaded microspheres in a human head-and-neck xenograft/nude mouse model. When atRA-loaded microspheres were administered s.c. at 200 mg/kg body weight to athymic nude mice, plasma concentration of atRA could be maintained in a range of 1.2 to 3.7 x 10(-8) M for 4 weeks. As a result, the tumor volume of human head-and-neck cancer was reduced compared to the control group by 51.3% (p < 0.01) at 14 days and by 49.2% (p < 0.05) at 28 days.

Monitoring of isotretinoin therapy by measuring the plasma levels of isotretinoin and 4-oxo-isotretinoin. A useful tool for management of severe acne

BACKGROUND

Isotretinoin for oral therapy in severe acne conglobata and acne nodulocystica represents a significant achievement; however, the drug exerts several mucocutaneous and systemic adverse effects, besides its teratogenic potency.

OBJECTIVE

The aim of this study was to investigate the plasma levels of isotretinoin and of 4-oxo-isotretinoin over long-term treatment of severe acne and to assess any correlation with the given dose, the clinical improvement and the occurrence of side effects.

METHODS

Forty-one patients with severe acne and acne-related disorders were studied under long-term oral intake of isotretinoin. Therapeutic effects and side effects were evaluated prior, during and at the end of therapy. The plasma levels of isotretinoin and of its major metabolite 4-oxo-isotretinoin were measured by reversed-phase HPLC and were correlated with the administered oral dose and the number and frequency of side effects.

RESULTS

Dose-dependent plasma levels of isotretinoin and its metabolite were observed. At a mean dosage of 0.75-1.0 mg/kg/day, 404 +/- 142 ng/ml were measured, whereas the plasma levels of 4-oxo-isotretinoin were 1-2x higher. The plasma levels correlated well with the orally administered dose of isotretinoin and the observed mucocutaneous side effects.

CONCLUSION

The study demonstrates that measuring of the plasma levels may be a helpful tool to monitor the individual therapeutic dose regimen in patients with severe acne in order to minimize undesired side effects and to control oral intake.

Pilot trial of the safety, tolerability, and retinoid levels of N-(4-hydroxyphenyl) retinamide in combination with tamoxifen in patients at high risk for developing invasive breast cancer

PURPOSE

N-(4-hydroxyphenyl) retinamide (¿4-HPR, Fenretinide; R.W. Johnson Pharmaceutical Research Institute, Springhouse, PA) and tamoxifen (TAM) have synergistic antitumor and chemopreventive activity against mammary cancer in preclinical studies. We performed a pilot study of this combination in women at high risk for developing breast cancer.

PATIENTS AND METHODS

Thirty-two women were treated with four cycles of 4-HPR, 200 mg orally (PO) for 25 days of each 28-day cycle, and TAM, 20 mg PO once daily for 23 months beginning after 1 month of 4-HPR alone. Tolerability, dark adaptometry, tissue biopsies, and retinoid plasma concentrations (Cp) were evaluated.

RESULTS

Symptomatic reversible nyctalopia developed in two patients (6%) on 4-HPR, but 16 (73%) of 22 patients had reversible changes in dark adaptation, which correlated with relative decrease in Cp retinol (P </=.01). Four patients stopped treatment for side effects, and 84% of patients had hot flashes. Other commonly reported (grade </= 2) reversible toxicities included skin and ocular dryness, fatigue, and mood changes. Serum high-density lipoprotein increased and cholesterol decreased from baseline to month 4. Baseline mean +/- SD Cp retinol was 708 +/- 280 ng/mL. Mean +/- SD Cp of 4-HPR, N-(4-methoxyphenyl) retinamide (4-MPR), and retinol after 1 month of 4-HPR were 0.34 +/- 0.21 micromol/L, 0.28 +/- 0.21 micromol/L, and 282 +/- 127 ng/mL, respectively. Mean retinoid Cps did not change after 3 months of 4-HPR + TAM.

CONCLUSIONS

TAM administration did not affect Cp 4-HPR or 4-MPR. Reversible nyctalopia correlated with relative decrease in Cp retinol but was not symptomatic for most patients. TAM + 4-HPR has acceptable tolerability for this high-risk cohort.

Supercritical fluid extraction of 13-cis retinoic acid and its photoisomers from selected pharmaceutical dosage forms

13-Cis retinoic acid (Accutane) was extracted from a cream, gel, capsule and beadlet dosage from using supercritical carbon dioxide modified with 5% methanol as the mobile phase. The pump pressure and the extraction chamber and restrictor temperature were experimentally optimized at 325 atm and 45 degrees C, respectively. A 2.5-min static and 5-min dynamic extraction time were used. The supercritical fluid extraction (SFE) eluent was trapped in methanol, injected into the high-performance liquid chromatographic (HPLC) system, and quantitated by ultraviolet detection at 360 nm. Application of the SFE method to spiked placebo dosage forms gave 13-cis retinoic acid recoveries of 98.8, 98.9, 98.8 and 100% for the cream, gel, capsule and beadlet, respectively, with R.S.D.s in the range 0.6-0.9% (n = 4). Inter-day percent error and precision of the extraction were 1.1-2.0 and 0.2-2.4% (n = 3), respectively, and intra-day percent error and precision were 1.0-3.0 and 0.3-2.1% (n = 8), respectively. Percent error and precision data for spiked celite samples in the 0.05-1.0 microgram ml-1 range were 0.59-4.75 and 1.8-2.1% (n = 3), respectively. The extraction method was applied to commercial 13-cis retinoic acid dosage forms and the results compared to unextracted samples. Linear regression analysis of concentration versus peak height gave a correlation coefficient of 0.9991 with a slope of 7.468 and a y-intercept of 0.1923. The percent error and precision data were 1.3-5.3 and 0.2-1.5% (n = 4), respectively. The photoisomers of 13-cis retinoic acid were also extracted with the method and recoveries of 90.4-92.4% with R.S.D.s of 1.5-3.4% were obtained (n = 4).

All-trans retinoic acid and interferon-alpha-2a in patients with metastatic or recurrent carcinoma of the uterine cervix: clinical and pharmacokinetic studies. New York Gynecologic Oncology Group

BACKGROUND

Recent clinical trials with a combination of interferon (IFN alpha) and 13 cis-retinoic acid resulted in high response rates among women with locally advanced and metastatic carcinoma of the uterine cervix. The authors sought to amplify these observations by employing the isomer of 13 cis-retinoic acid, all-trans retinoic acid (tRA), in combination with IFN alpha.

METHODS

Sequential clinical trials were initiated by the New York Gynecologic Oncology Group to test the combination of tRA and IFN alpha in women with metastatic or recurrent carcinoma of the cervix who had failed primary therapy. IFN alpha was administered at 6 MU subcutaneously 3 times per week. In the first trial, tRA was administered at 50 mg/m2 orally 3 times per day on a daily schedule (daily regimen), whereas in the second trial, tRA was administered at the same dose 3 times per day, but only on Days 1-3 each week (intermittent schedule). Clinical outcomes included response to therapy and survival. Plasma pharmacokinetic studies of tRA were performed in both trials to assess the effects of different schedules on plasma levels of the drug.

RESULTS

Fourteen women with metastatic or recurrent squamous cell carcinoma of the cervix were enrolled in the daily trial and 12 women in the intermittent trial. There was no clinical activity for either regimen, and both studies were terminated according to an early stopping rule. Because tRA has been reported to induce its own metabolism, plasma levels of tRA were measured on Days 1, 8, and 28. The change in the area under the time versus tRA concentration curve (AUC) was significantly different between the two groups. The average AUC on Day 8 was 14% of that observed on Day 1 for the daily treatment group; in contrast, it was 107% on Day 1 in the intermittent treatment group. In 6 of 8 patients studied in the daily trial, the AUC decreased at least 60% by either Week 2 or Week 4. In contrast, in the intermittent trial, only 3 of 9 patients experienced >60% decrease in plasma levels of the drug at either Day 8 or Day 28.

CONCLUSIONS

The combination of tRA + IFN alpha was inactive in patients with advanced carcinoma of the cervix when employed at these doses on either the daily or intermittent schedule. The failure of activity of this regimen did not result from induction of metabolism of tRA, suggesting that intrinsic mechanisms of resistance to tRA at the cellular level may be of greater importance.

Quantitative high-performance liquid chromatographic determination of retinoids in human serum using on-line solid-phase extraction and column switching. Determination of 9-cis-retinoic acid, 13-cis-retinoic acid, all-trans-retinoic acid, 4-oxo-all-trans-retinoicacid and 4-oxo-13-cis-retinoic acid

A fully automated isocratic high-performance liquid chromatographic method for the determination of 9-cis-retinoic acid, 13-cis-retinoic acid, all-trans-retinoic acid, 4-oxo-13-cis-retinoic acid and 4-oxo-all-trans-retinoic acid, has been developed using on-line solid-phase extraction and a column switching technique allowing clean-up and pre-concentration in a single step. A 500-microliter sample of serum was diluted with 750 microliters of a solution containing 20% acetonitrile and the internal standard 9,10-dimethylanthracene. About 1000 microliters of this mixture was injected on a 20 x 4.6 mm I.D. poly ether ether ketone (PEEK) pre-column with titanium frits packed with Bondapak C18, 37-53 microns, 300 A particles. Proteins and very polar compounds were washed out to waste, from the pre-column, with 0.05% trifluoroacetic acid (TFA)-acetonitrile (8.5:1.5, v/v). More than 200 aliquots of diluted serum could be injected on this pre-column before elevated back-pressure enforces replacement. Components retained on the pre-column were backflushed to the analytical column for separation and detection at 360 nm. Baseline separation was achieved using a single 250 x 4.6 mm I.D. Suplex pKb-100 column and a mobile phase containing 69:10:2:16:3 (v/v) of acetonitrile-methanol-n-butanol-2% ammonium acetate-glacial acetic acid. A total time of analysis of less than 30 min, including sample preparation, was achieved. Recoveries were in the range of 79-86%. The limit of detection was 1-7 ng/ml serum and the precision, in the concentration range 20-1000 ng/ml, was between 1.3 and 4.5% for all five compounds. The method was applied for the analysis of human serum after oral administration of 60 mg Roaccutan. The method is well suited for pharmacological studies, while the endogenous levels of some retinoic acid isomers are below the limit of quantitation.

A developmental toxicity study of tretinoin emollient cream (Renova) applied topically to New Zealand white rabbits

BACKGROUND

Embryofetal developmental toxicity associated with oral administration of vitamin A analogs has led to concern about risks from topical application.

OBJECTIVE

This study was conducted to evaluate the potential developmental toxicity of tretinoin emollient cream when applied to the skin of pregnant New Zealand white rabbits during organogenesis (gestational days 7 through 19).

METHODS

Twenty rabbits each were randomly assigned to a control group (group I) or to receive vehicle (group II) or tretinoin emollient cream topically at dosages of 10 (0.05 mg/kg*, group III) or 100 (0.5 mg/kg*, group IV) times that used clinically in humans. Does and fetuses were examined for tretinoin-induced toxic effects, and maternal plasma tretinoin and metabolite levels were measured.

RESULTS

The rate of abortion was increased significantly in does in group IV (p < or = 0.01) compared with the control group. Dosage-dependent increases in incidence and severity of skin reactions occurred in groups administered the vehicle and the two dosages of tretinoin. Does in groups III and IV had clinical and necropsy observations that were considered direct or indirect effects of tretinoin administration, persistent weight loss, and reduced feed consumption. Maternal endogenous plasma tretinoin levels were below the lower limit of quantitation of 5 ng/ml and were not significantly altered with treatment. Group IV had significantly reduced mean fetal body weight (p < or = 0.01) and a greater frequency of resorptions compared with group I. Although external, visceral, or skeletal alterations occurred at significantly greater levels in group III, they were unrelated to tretinoin administration because the fetal incidences were not dosage dependent, and the litter incidence did not significantly differ from the control group values.

CONCLUSION

Maternally toxic dosages of tretinoin were associated with an increased incidence of abortions and resorptions and reduced fetal body weight, two end points of developmental toxicity. Consistent with the absence of detectable tretinoin plasma levels, however, no changes in fetal morphology were attributable to tretinoin administration. *The milligrams per kilogram dosage refers to the amount of active ingredient (tretinoin). The 0.05 mg/kg and 0.5 mg/kg groups were treated with 0.005% and 0.05% wt/wt tretinoin emollient cream formulation. The 0.05% tretinoin emollient cream is the Renova clinical formulation. The 10 and 100 times clinical multiples refer to Renova clinical multiples and are based on a 50 kg adult patient's applying 500 mg of 0.05% tretinoin emollient cream formulation daily to yield a clinical dosage of 0.005 mg/kg.

Simultaneous determination of all-trans-, 13-cis-, 9-cis-retinoic acid and their 4-oxo-metabolites in plasma by high-performance liquid chromatography

A gradient reversed-phase high-performance liquid chromatographic technique is described for the easy separation and quantification of some retinoids; all-trans-retinoic acid, 13-cis-retinoic acid, 9-cis-retinoic acid and their corresponding 4-oxometabolites, in plasma. The method involved a diethyl ether-ethyl acetate (50:50, v/v) mixture extraction at pH 7 with acitretin and 13-cis-acitretin as internal standards. A Nova-Pak C18 steel cartridge column was used. The mobile phase was methanol-acetonitrile (65:35, v/v) and 5% tetrahydrofuran (solvent A) and 2% aqueous acetic acid (solvent B) at 1 ml/min. The gradient composition was (only the percentages of solvent B are mentioned): I, 25% solvent B at the time of injection; II, 12% solvent B at 11 min until min; III, 25% solvent B and maintenance of 25% solvent B for 10 min until a new injection. Total time between injections was 40 min. Detection was by absorbance at 350 nm. The precision calculated for plasma concentrations ranging from 2 to 250 ng/ml was better than 15% and the accuracy was less than 12%. The linearity of the method was in the range of 2 to 400 ng/ml of plasma. The limit of quantification was 2 ng/ml for each of the compounds. The HPLC method was applied to plasma specimens collected from animals receiving single dose administrations of all-trans-retinoic acid, 13-cis-retinoic acid and 9-cis-retinoic acid.

Isocratic reversed-phase liquid chromatography of all-trans-retinoic acid and its major metabolites in new potential supplementary test systems for developmental toxicology

An isocratic reversed-phase high-performance liquid chromatographic procedure for the determination of all-trans-retinoic acid (all-trans-RA) and its metabolites, all-trans-4-oxo-RA, 5,6-epoxy-RA, 9-cis-RA and 13-cis-RA, in mouse plasma and embryo and in new in vitro potential test systems for developmental toxicology has been developed. These compounds, their biological precursor retinol (vitamin A) and the internal standard were resolved on a Spherisorb ODS-2 (5 microns) column (250 x 4.6 mm I.D.) with acetonitrile-water-methanol-n-butyl alcohol (56:37:4:3, v/v) containing 100 mM ammonium acetate and 70 mM acetic acid as the elution system, with a total run time of 23 min. The assay was linear over a wide range, with a lower limit of quantitation of 50 ng/ml or 10 ng/mg of protein for all-trans-RA, 13-cis-RA and 9-cis-RA and of 25 ng/ml or 5 ng/mg protein for the 4-oxo- and 5,6-epoxy-metabolites. At these concentrations, intra-assay coefficients of variation (C.V.) of the retinoids were 3-9%. Mean intra-assay C.V. averaged 5-7% in the tissues studied. Its use is discussed for RA measurements in some of the new test systems--Drosophila melanogaster, sea urchin embryos and cultured human keratinocytes--that have to be evaluated in toxicological testing, supplementary to standard assays in mammals.

Retinoic acid isomers applied to human skin in vivo each induce a 4-hydroxylase that inactivates only trans retinoic acid

Application of all-trans retinoic acid to human skin for 4 d under occlusion produces a marked increase in retinoic acid 4-hydroxylase activity. In this study, the possible induction of other hydroxylase in response to 9-cis and 13-cis retinoic acid application to adult human skin in vivo was determined. Application of 0.1% all-trans, 0.1% 9-cis, and 0.1% 13-cis retinoic acid to human skin for 2 d resulted in induction of only all-trans retinoic acid 4-hydroxylase activity. The 4-hydroxylase activity in microsomes from the treated tissue ranged from 838 +/- 46 to 531 +/- 59 pg of 4- hydroxy all-trans retinoic acid formed/min/mg protein (n=6). These same preparations were unable to use 9-cis or 13-cis retinoic acid as substrate for the hydroxylation reaction. Extraction of the retinoic acid isomers from epidermis 48 h after application of 0.1% solution of each isomer yielded significant amounts of all-trans retinoic acid (36-72%) regardless of the isomer applied. The all-trans isomer produced by isomerization of both 9-cis and 13-cis retinoic acids is the likely inducer of the 4-hydroxylase. All-trans retinol and all-trans retinal were unable to compete with all-trans retinoic acid as substrate for 4-hydroxylase enzyme. The 4-hydroxylase induced in response to pharmacological doses of retinoic acids is specific for the all-trans isomer. The inability of 9-cis or 13-cis retinoic acid to induce their own hydroxylation and inactivation or act as substrate for the 4-hydroxylase in skin may have considerable implications in light of the clinical use of retinoids in the treatment of various diseases including cancers.

Inhibition of all-trans-retinoic acid metabolism by fluconazole in vitro and in patients with acute promyelocytic leukemia

All-trans-retinoic acid induces acute promyelocytic leukemia cell differentiation in vitro, and it produces greater than 90% complete remissions in patients with acute promyelocytic leukemia. Despite the high response rate, the majority of patients relapse with continued trans-retinoic acid therapy, and disease progression has been observed to be accompanied by an increase in the metabolism of trans-retinoic acid in the patients. In this study, the pharmacokinetic disposition of trans-retinoic acid was determined by HPLC in patients with acute promyelocytic leukemia before and after concurrent therapy with the triazole antimycotic agent fluconazole. Treatment with trans-retinoic acid for 1 week reduced the area under the plasma trans-retinoic acid concentration vs time curve in one patient by 67%, from 277 to 91 ng/mL/hr. Trans-retinoic acid pharmacokinetics were repeated after the second dose of fluconazole, administered 1 hour prior to the retinoid, and the AUC was found to be 401 ng/mL/hr, a greater than 4-fold increase from the pre-fluconazole level. A similar, though more modest, effect of fluconazole was seen in a second acute promyelocytic leukemia patient. The effect of fluconazole on trans-retinoic acid metabolism was examined in vitro using isolated human hepatic microsomes. Fluconazole inhibited the NADPH-dependent cytochrome P450-mediated catabolism of trans-retinoic acid in a concentration-dependent manner. Although fluconazole was approximately one-half as potent an inhibitor when compared with ketoconazole, a related antifungal drug, 60-90% inhibition was observed at the concentrations of fluconazole measured in the acute promyelocytic leukemia patients. Neither fluconazole nor ketoconazole inhibited lipid hydroperoxide-mediated metabolism of trans-retinoic acid. Since fluconazole is a well-tolerated agent frequently administered to leukemia patients, its use in combination with trans-retinoic acid merits further consideration.

Chromatographic and electrophoretic analysis of biomedically important retinoids

The determination of retinol (vitamin A) and its metabolites, as well as synthetic retinoids, in biological samples is a challenging task due to the sensitivity of these compounds to light, heat and oxygen, high protein binding, separation of geometric isomers and determination of low endogenous levels. Numerous procedures for sample preparation have been published for biological fluids and tissues, consisting of solvent extraction, solid-phase extraction (off-line) and HPLC with column switching (on-line solid-phase extraction). The last-mentioned technique has several advantages, including a high degree of automation, no evaporation of extraction solvents, protection from light and higher sensitivity. Due to the favourable UV characteristics of most retinoids, HPLC with UV detection is most often employed, and photodiode array detection is becoming more and more popular. Fluorescence and electrochemical detection have found only a limited field of application, but the use of LC-MS resulted in a few highly sensitive methods. Reconsideration of GC through the use of better deactivated columns and cold on-column injection and evaluation of new promising separation methods, such as supercritical fluid chromatography and capillary electrophoresis, have shown preliminary encouraging results, but appear to reach the required sensitivity only by coupling to MS. Therefore, HPLC with UV detection is still the method of choice for highly sensitive and selective retinoid determination, as well as for high sample throughput and robustness.

Simultaneous determination of etretinate, acitretin and their metabolites in perfusate, perfusate plasma, bile or hepatic tissue with reversed-phase high-performance liquid chromatography

Etretinate is a synthetic aromatic retinoid used in the treatment of psoriasis and other disorders affecting the skin. Acitretin is the primary active metabolite of etretinate. The in situ perfused rat liver model was used to study the first-pass hepatic metabolism of etretinate and acitretin and a reliable method of quantifying etretinate and its metabolites was needed. Previously published assays allow for the simultaneous quantitation of etretinate and acitretin in blood or plasma. This paper describes an accurate and reliable reversed-phase HPLC method for the determination of etretinate, acitretin and their metabolites in whole perfusate, plasma, bile and hepatic tissue.

Simultaneous determination of all-trans and 13-cis retinoic acids and their 4-oxo metabolites by adsorption liquid chromatography after solid-phase extraction

All-trans retinoic acid (all-trans RA), the active metabolite of vitamin A, has been demonstrated to be an efficient alternative to chemotherapy in the treatment of acute promyelocytic leukemia (APL), the AML3 subtype of the FAB cytological classification. Complete remission is obtained by inducing terminal granulocytic differentiation of the leukemic cells. To study all-trans RA pharmacokinetics in patients with APL, a rapid, precise and selective high-performance liquid chromatographic (HPLC) assay was developed. This method is easy and shows good repeatability (C.V. = 8.41-12.44%), reproducibility (C.V. = 9.19-14.73%), accuracy (C.V. = 3.5-11%) and sensitivity with a detection limit of 5 pmol/ml. The analysis is performed using normal-phase HPLC in an isocratic mode with UV detection after solid-phase extraction on octadecyl (C18) columns. The mobile phase is hexane-dichloromethane-dioxane (78:18:4, v/v) containing 1% acetic acid.

Determination of orally administered all-trans-retinoic acid in human plasma by high-performance liquid chromatography

All-trans-retinoic acid (RA) is used successfully in the treatment of acute promyelocytic leukaemia (APL), although unexplained relapses occur in many of the patients. Pharmacokinetic studies may help in understanding the mechanism of resistance to RA and a simple and rapid procedure for its determination in biological samples may be advantageous. A high-performance liquid chromatographic procedure is described, involving one-step extraction of RA from plasma, isocratic elution from a reversed-phase column (LiChrosorb RP-18, 5-microns particle size) and UV detection at 340 nm. The calibration graph is linear over a wide range and the limit of detection is approximately 10 ng/ml, using 0.5 ml of human plasma. The method is selective for RA, accurate and robust and thus suitable for the routine analysis of plasma samples from patients undergoing RA therapy. Analysis of plasma in a patient on RA therapy (45 mg/m2 per day) confirmed that during continuous treatment with RA the drug plasma concentrations are markedly lower at the time of relapse than on the first day of treatment.

Altered proliferation, synthetic activity, and differentiation of cultured human sebocytes in the absence of vitamin A and their modulation by synthetic retinoids

Human sebocytes maintained in medium containing delipidized serum were studied for ultrastructural characteristics, cell proliferation, lipid synthesis, immunophenotype, and keratin expression before and after the addition of the synthetic retinoids isotretinoin and acitretin (10(-8)-10(-5) M). Compared to the properties of sebocytes cultured in normal sebocyte medium (1-2 x 10(-7) M vitamin A), the use of delipidized serum (undetectable amounts of vitamin A) resulted in prominent decrease of i) proliferation; ii) number of intracellular lipid droplets and synthesis of total lipids, especially triglycerides, squalene, and wax esters; and iii) labeling with monoclonal antibodies identifying progressive and late-stage sebocyte differentiation. Intercellular spaces narrowed and cell-to-cell contacts were established by abundant desmosomes. Lanosterol was induced. Keratins 14, 16, 17, and 18 were upregulated and the keratin 16: keratin 4 ratio, negatively correlating with sebocyte differentiation, increased. Addition of isotretinoin and acitretin exerted a biphasic effect. At concentrations < or = 10(-7) M, both compounds enhanced sebocyte proliferation and synthesis of total lipids, especially triglycerides and cholesterol, and decreased lanosterol, keratin 16, and the keratin 16:keratin 4 ratio. In contrast, retinoid concentrations > 10(-7) M inhibited sebocyte proliferation in a dose-dependent manner. Our findings indicate that vitamin A is essential for proliferation, synthetic activity, and differentiation of human sebocytes in vitro. Synthetic retinoids partially reinstate the altered functions of sebocytes maintained in medium containing delipidized serum. In contrast to the previously shown isotretinoin-specific response of cultured sebocytes in the presence of vitamin A, similar effects of isotretinoin and acitretin were obtained in its absence. This suggests different interactions of synthetic retinoids with vitamin A, possibly influencing their efficacy on the sebaceous gland.

The role of the human placenta in embryonic nutrition. Impact of environmental and social factors

The human placenta has been implicated in the poor growth and development of the embryo/fetus due to alterations in blood flow and reductions in the transfer of nutrients such as amino acids and carbohydrates. Deficiencies of such nutrients have been the principal of many research investigations. The role of micronutrients, however, may also be major factors in appropriate growth and development, and there may be a general reduction in the availability of such nutrients, for example, the role of folate supplementation during early pregnancy and the reduction in the incidence of neural tube defects. Vitamins are not all transported via a common mechanism. Therefore, the modulation of human placental transport can be different for different vitamins, for example, A and B12. It is apparent that the human placenta can oxidatively metabolize retinoids (isotretinoin and tretinoin) to more toxic or less toxic metabolites. These metabolites can then be transferred to the fetal circulation. Such metabolism/transfer is in contrast to how vitamin B12 is bound to transcobalamin proteins, which are produced by the placenta and directionally released into the maternal and fetal circulations.

Human skin levels of retinoic acid and cytochrome P-450-derived 4-hydroxyretinoic acid after topical application of retinoic acid in vivo compared to concentrations required to stimulate retinoic acid receptor-mediated transcription in vitro

Metabolism of retinoic acid to a less active metabolite, 4-hydroxyretinoic acid, occurs via cytochrome P-450 isozyme(s). Effect of a pharmacological dose of retinoic acid on the level of retinoic acid in skin and on cytochrome P-450 activity was investigated. A cream containing 0.1% retinoic acid or cream alone was applied topically to adult human skin for four days under occlusion. Treated areas were removed by a keratome and a microsomal fraction was isolated from each biopsy. In vitro incubation of 3H-retinoic acid with microsomes from in vivo retinoic acid treated sites resulted in a 4.5-fold increase (P = 0.0001, n = 13) in its transformation to 4-hydroxyretinoic acid in comparison to in vitro incubations with microsomes from in vivo cream alone treated sites. This cytochrome P-450 mediated activity was oxygen- and NADPH-dependent and was inhibited 68% by 5 microM ketoconazole (P = 0.0035, n = 8) and 51% by carbon monoxide (P = 0.02, n = 6). Cotransfection of individual retinoic acid receptors (RARs) or retinoid X receptor-alpha (RXR-alpha) and a chloramphenicol acetyl transferase (CAT) reporter plasmid containing a retinoic acid responsive element into CV-1 cells was used to determine the ED50 values for stimulation of CAT activity by retinoic acid and its metabolites. Levels of all trans and 13-cis RA in RA-treated tissues were greater than the ED50 values determined for all three RARs with these compounds. Furthermore, the level of all trans RA was greater than the ED50 for RXR-alpha whereas the 4-OH RA level was greater than the ED50 for RAR-beta and RAR-gamma but less than for RAR-alpha and RXR-alpha. These data suggest that there are sufficient amounts of retinoic acid in treated skin to activate gene transcription over both RARs and RXR-alpha.

Simple reversed-phase high-performance liquid chromatographic method for 13-cis-retinoic acid in serum

An isocratic reversed-phase high-performance liquid chromatographic method for the analysis of 13-cis-retinoic acid in serum is developed. Sample preparation includes deproteination with acetonitrile-perchloric acid-acetic acid followed by centrifugation. 9-Methylanthracene is used as the internal standard. Chromatographic separation is achieved on a C18 column (Zorbax) using an acetonitrile-aqueous 0.5% acetic acid (85:15, v/v) eluent containing 0.05% (w/v) sodium hexanesulfonate. The limit of detection is 12 ng/ml in serum, using 0.5 ml samples. Quantitative recoveries and excellent intra-day and inter-day precision are reported.

Quantification of acitretin in human plasma by microbore liquid chromatography-negative chemical ionization mass spectrometry

A highly sensitive liquid chromatographic-mass spectrometric procedure has been developed to quantitate plasma concentrations of acitretin, a dermatologic agent used to treat severe psoriasis. The assay utilizes the combination of normal-phase microbore high-performance liquid chromatography, negative chemical ionization mass spectrometry, selective ion monitoring and stable isotope dilution. The method has been used to measure acitretin and its metabolite, 13-cis-acitretin, over a range of 1-20 ng/ml in human plasma. The inter-assay precision was 5.3% for acitretin and 3.9% for 13-cis-acitretin, while the intra-assay precisions for acitretin and 13-cis-acitretin were 10.8 and 12.7%, respectively. Reproducibility of the assay for acitretin and 13-cis-acitretin, which was determined by the relative standard deviation of multiple analyses of the same quality assurance sample, was 5.9 and 8.1%, respectively.

The negligible systemic availability of retinoids with multiple and excessive topical application of isotretinoin 0.05% gel (Isotrex) in patients with acne vulgaris

The potential systemic availability of retinoids from topically applied isotretinoin was assessed in 12 men with acne vulgaris. Isotretinoin 0.05% gel was applied to patients at a daily dose of 20 gm (equivalent to 10 mg of isotretinoin) over a 1900 cm2 surface area of skin on the face, back, and chest for 30 days. Blood samples were collected throughout the study and up to 48 hours after the last topical application; they were assayed for isotretinoin, tretinoin, and 4-oxo-isotretinoin by specific high-performance liquid chromatography. Plasma concentrations of isotretinoin, tretinoin, and 4-oxo-isotretinoin were not measurable (less than 20 ng/ml) at any time. Most adverse experiences were cutaneous; a few systemic adverse experiences were judged to be remotely related to topical drug administration. The lack of measurable plasma concentrations of isotretinoin, tretinoin, or 4-oxo-isotretinoin and systemic adverse experiences indicates negligible systemic availability of retinoids even after multiple application of isotretinoin 0.05% gel at doses approximately 12 times greater than normal daily use.

Chromatography of retinoids

This article reviews the determination of retinoic acids and their metabolites (first-generation retinoids), aromatic retinoids (second generation) and arotinoids (third generation) in biological samples. Because of the sensitivity of the retinoids to isomerization and oxidation, special care has to be taken from sample collection and storage, throughout extraction, till the final chromatographic separation. High and strong protein binding, and insolubility in aqueous solutions hamper the extraction from biological samples. Various extraction procedures are discussed, mainly involving liquid-liquid extraction of biological fluids or lyophilized tissue samples. The new technique involving direct injection of biological fluids or tissue homogenates, using high-performance liquid chromatography (HPLC) with automated column switching, provides full protection from light and simplifies sample work-up. HPLC with ultraviolet detection is the method of choice for the determination of retinoids, because it is rapid, sensitive and allows separation of geometric isomers and metabolites within a wide polarity range. Gas chromatography-mass spectrometry is not appropriate for first- and second-generation retinoids because of isomerization, but allows very sensitive determination of third-generation retinoids, although very extensive sample clean-up and derivatization are necessary. However, direct injection of large volumes of biological fluids into HPLC systems, using on-line solid-phase extraction and automated column-switching, results in very sensitive methods even with simple ultraviolet detection and may become the method of choice for routine analyses.

Vitamin A supplementation increases levels of retinoic acid compounds in human plasma: possible implications for teratogenesis

The concentrations of retinoic acid compounds were monitored by a newly developed highly sensitive HPLC procedure in plasma of six volunteers who received 833 IU vitamin A per kg body weight per day during a 20-day period. There was a significant increase of all-trans-retinoic acid (two-fold), 13-cis-retinoic acid (7-fold) and 13-cis-4-oxoretinoic acid (5-fold) over endogenous plasma levels of these retinoids. The same compounds had previously been found after treatment with the teratogenic drug isotretinoin (Roaccutan, Accutane). Our results raise the possibility that high vitamin A intake may carry a teratogenic risk attributable to increased levels of retinoic acid compounds generated from retinol by metabolic processes.

Teratogenicity of etretinate during early pregnancy in the rat and its correlation with maternal plasma concentrations of the drug

Sprague-Dawley female rats were treated with a single oral dose of 0 (vehicle), 10, or 25 mg/kg of etretinate (ET), an aromatic retinoid, on gestation day 6, 7, or 8. While treatment on day 8 with both dosages of ET was highly teratogenic, no evidence of embryotoxicity, considered to be treatment related, was observed when the same doses were administered on day 6 or 7. We concluded that the rat embryo is not susceptible to teratogenic effects of ET on gestation day 6 or 7 and that day 8 is the earliest susceptible period for ET teratogenesis. This may well be true of retinoids as a class since we have observed similar results for all-trans- and 13-cis-retinoic acids (unpublished findings). In another study, mated rats were treated with a single oral dose of ET on day 8. No evidence of embryotoxicity was observed at dosages of 1, 3, and 6 mg/kg; in contrast, treatment with 10, 15, or 25 mg/kg of ET resulted in an increasingly greater number of malformed fetuses and resorptions. Plasma concentrations of ET and three metabolites [acitretin (AC), 13-cis-etretinate (13-cis-ET), and 13-cis-acitretin (13-cis-AC)) were determined in mated rats given a single oral non-teratogenic (3 or 6 mg/kg) or teratogenic (10 or 25 mg/kg) dose of ET on gestation day 8. The AUC0----24hr values of ET and AC, the major metabolite and suspected proximal teratogen, were roughly proportional to the administered dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Teratogenicity of the 13-cis and all-trans-isomers of the aromatic retinoid etretin: correlation to transplacental pharmacokinetics in mice during organogenesis after a single oral dose

NMRI mice were treated on day 11 (day 0 = plug day) of gestation with a single oral dose of 100 mg/kg of either all-trans-etretin (acitretin) or 13-cis-etretin. For teratology studies mice were sacrificed on day 18 of gestation, and the fetuses were examined for malformations. For pharmacokinetic studies, groups of 5 mice were sacrificed after 5, 10, and 30 min and 1, 2, 4, and 8 h. The concentrations of retinoids in maternal plasma and in embryos were determined by a newly developed HPLC gradient method. All-trans-etretin induced malformations in 94% of the fetuses, mainly in fore and hind limbs and cleft palate. 13-cis-etretin did not show any teratogenic or embryo-lethal effects at the dose level used. These findings could be explained by a transplacental pharmacokinetic study. The maximum peak level and also the AUC (area under the concentration-time curve) value of all-trans-etretin in the embryos was 7-8 times higher than corresponding values for 13-cis-etretin, probably due to extensive transport of the trans-isomer and limited transport of the cis-isomer from maternal plasma to the embryos. The concentration quotient between embryo and the maternal plasma was between 0.43 and 1.10 for all-trans-etretin, and only 0.16-0.31 for 13-cis-etretin over the time period studied. An in vivo isomerization of the compounds was also observed which was more extensive for 13-cis-etretin than for all-trans-etretin. Our results indicate that the low teratogenic potency of 13-cis-etretin is due to a limited placental transfer of this compound; on the other hand, the potent teratogen all-trans-etretin is rapidly and extensively transferred to the embryo.

Human biliary metabolites of isotretinoin: identification, quantification, synthesis, and biological activity

1. The metabolites of isotretinoin (13-cis-retinoic acid, Accutane) were investigated in the bile of two patients with biliary T-tube drainage after administration of a single, oral, 80-mg dose of 14C-isotretinoin. Radioactivity measurements showed that the two patients excreted 22.7 and 17.1% of the dose in their bile in 4 days. 2. The two major drug-related components in the bile were identified as the glucuronide conjugates of 4-oxo-isotretinoin and 16-hydroxy-isotretinoin. Two minor components were identified as the glucuronide conjugates of isotretinoin and 18-hydroxy-isotretinoin. 3. H.p.l.c. analyses of Glusulase-treated bile samples indicated that the glucuronides of isotretinoin and the two major metabolites accounted for about 48% and 44% of the total radioactivity in the bile of the two patients. 4. Racemic 16-hydroxy-isotretinoin was synthesized and evaluated for its effect on human sebocytes in vitro. This metabolite and the other major metabolites of isotretinoin were less active than isotretinoin in inhibiting the proliferation of the sebocytes.

Quantitative analysis of retinoids in biological fluids by high-performance liquid chromatography using column switching. II. Simultaneous determination of etretinate, acitretin and 13-cis-acitretin in plasma

An automated gradient high-performance liquid chromatographic method for the determination of etretinate, acitretin and 13-cis-acitretin in plasma was developed, using a column-switching technique. After protein precipitation with ethanol, 0.5 ml of the supernatant was injected onto a precolumn (17 mm x 4.6 mm I.D.), filled with 37-53 microns C18 Corasil. Polar plasma components were washed out using 1% ammonium acetate and 1% acetic acid-acetonitrile (8:2, v/v); the retained retinoids were then transferred to the analytical column (125 mm x 4 mm I.D., filled with 5-microns ODS material) in the backflush mode, separated by gradient elution and detected at 360 nm by UV detection. The limit of quantification was 2 ng/ml and the inter-assay precision in the concentration range 20-1000 ng/ml was between 0.9 and 4.0% for all three compounds. To optimize the recovery for etretinate (greater than 60%), protein was precipitated from plasma with ethanol before injection, instead of direct injection of plasma samples, and a mobile phase containing 20% acetonitrile, instead of pure water or buffer, was used.

Pharmacokinetics of 14C-etretinate in healthy volunteers and two patients with biliary T-tube drainage

The pharmacokinetic profile of 14C-etretinate, a retinoid that is effective in the treatment of psoriasis, was studied in six healthy male volunteers and two biliary T-tube patients. Following a 100 mg oral dose of 14C-etretinate (20 microcurie), etretinate and its major blood metabolites (etretin, isoetretin) were measured by HPLC and total carbon-14 was measured in blood, bile, urine, and feces by liquid scintillation counting. Etretinate was extensively metabolized in healthy volunteers and in T-tube patients. During the absorption phase, 75 per cent of the total radioactivity in the blood could be accounted for as etretinate, etretin, and isoetretin whereas these compounds accounted for only approximately 12 per cent of the blood radioactivity in T-tube patients over the same time period. The blood concentrations of etretinate, etretin, and isoetretin appeared to be substantially reduced in T-tube patients compared to those in healthy volunteers. A higher proportion of the total drug was excreted in the feces and bile of the T-tube patients (84 per cent) than in the feces of healthy volunteers (62 per cent). The major factor responsible for the observed decrease in etretinate blood concentrations following biliary cannulation appears to be the reduced absorption of etretinate due to the elimination of solubilizing bile salts in the duodenum. Carbon-14 related material was detected in urine and feces for as long as 3 weeks in healthy subjects supporting the previous observation that a long terminal elimination half-life exists for etretinate, even following a single dose of the compound.