Determination of cisapride, its oxidation product, propyl and butyl parabens in pharmaceutical dosage form by reversed-phase liquid chromatography

A simple, rapid and reproducible high-performance liquid chromatography (HPLC) assay for cisapride, its oxidation product (OP), propyl and butyl parabens in a pharmaceutical formulation is described. Chromatography was performed at room temperature by pumping acetonitrile–20 mM phosphate buffer pH 7 (50:50, v/v) at 1.5 ml min⁻¹ through C₈ reversed-phase column. Cisapride, OP, propyl and butyl parabens were detected at 276 nm and were eluted at 9.7, 3.1, 5.1 and 7.1 min, respectively. Calibration plots were linear (r>0.999) for all compounds from 0.5 to 200 μg ml⁻¹ for cisapride and OP and 0.1–200 μg ml⁻¹ for propyl and butyl parabens. Detection limits for cisapride, OP, propyl and butyl parabens were 40, 46, 48 and 54 ng ml⁻¹, respectively. Forced degradation investigations showed that cisapride does not undergo degradation under heat, acidic and basic conditions but it was susceptible to oxidation. The proposed method was successfully applied to the assay of cisapride in the presence of preservatives and OP in a commercial suspension.     

Assay of artemether, methylparaben and propylparaben in a formulated paediatric antimalarial dry suspension

Two HPLC-UV methods are described for the separate determination of artemether (AM) and the combined preservatives, methylparaben and propylparaben in a pharmaceutical dosage form. These analytes are contained in a dry suspension with a high amount of non-soluble excipients, some of which can interfere with the analysis. This makes their separation and analysis of the actives complex. Moreover, due to the wide difference in concentrations, the three analytes could not be quantitated simultaneously. Artemether was analysed using a reversed-phase Nucleosil C(18) column [5 microm, 125 mm x 4 mm (i.d.)] with a mixture of acetonitrile: potassium phosphate buffer pH 5.0 (0.05 M): water [48:32:10 (v/v/v)] as mobile phase. Due to the low solubility of the hydroxy benzoic acid esters in water, their sodium salts were used in the formulation. Complete separation of these preservatives was achieved on the same type of column as artemether using as eluent acetonitrile: potassium phosphate buffer pH 5.0 (0.05 M) (30:70, v/v). Quantitation was achieved with UV detection at 215 nm for artemether and 254 nm for the parabens, respectively. And in both methods, pump flow rate was 1.0 ml/min, sample injection volume 20 microl, ambient temperature maintained and no prior sample extraction methods were necessary throughout the experiments. Calibration curves were linear at concentration ranges of 4-16 microg/ml, 1-4 microg/ml and 1-10 mg/ml for methylparaben, propylparaben and artemether respectively. The excipient powder interference could be eliminated by diluting the sample and the analytes eluted at relatively short times using these systems. Both methods were further validated in terms of specificity, linearity, precision and accuracy. The procedures prescribed here are simple, selective and can be used for routine quality control and stability indicating tests involving the analysed compounds formulated in complex matrices.     

Detection and Characterization of an Unknown Impurity in Levothyroxine Oral Solution Product: Implications for Formulation Development and Storage

An existing USP(2010) impurity method for levothyroxine drug substance was modified to expand its applicability for the analysis of levothyroxine oral solution (OS) formulation while achieving desirable resolution between the components of OS formulation. When analyzed using modified USP(2010) method, an unknown impurity was detected in one of the levothyroxine OS products. A systematic investigation of unknown impurity was carried out using a combination of chromatographic, mass spectral and physicochemical methods to understand the nature of this unknown impurity. A possible elucidation of chemical structure and reaction mechanism for the formation of this previously unreported impurity was proposed.     

Aromatase inhibiting and combined estrogenic effects of parabens and estrogenic effects of other additives in cosmetics

There is concern widely on the increase in human exposure to exogenous (anti)estrogenic compounds. Typical are certain ingredients in cosmetic consumer products such as musks, phthalates and parabens. Monitoring a variety of human samples revealed that these ingredients, including the ones that generally are considered to undergo rapid metabolism, are present at low levels. In this in vitro research individual compounds and combinations of parabens and endogenous estradiol (E(2)) were investigated in the MCF-7 cell proliferation assay. The experimental design applied a concentration addition model (CA). Data were analyzed with the estrogen equivalency (EEQ) and method of isoboles approach. In addition, the catalytic inhibitory properties of parabens on an enzyme involved in a rate limiting step in steroid genesis (aromatase) were studied in human placental microsomes. Our results point to an additive estrogenic effect in a CA model for parabens. In addition, it was found that parabens inhibit aromatase. Noticeably, the effective levels in both our in vitro systems were far higher than the levels detected in human samples. However, estrogenic compounds may contribute in a cumulative way to the circulating estrogen burden. Our calculation for the extra estrogen burden due to exposure to parabens, phthalates and polycyclic musks indicates an insignificant estrogenic load relative to the endogenous or therapeutic estrogen burden.     

Medications as a source of paraben exposure

BackgroundParabens are used as antimicrobial excipients in some pharmaceuticals. Parabens may adversely affect reproduction.ObjectivesDetermine whether paraben-containing medication contributes to high urinary paraben concentrations.MethodsIndividuals at a fertility clinic provided multiple urine samples during evaluation/treatment and reported 24-h use of medications and personal care products (PCP). Repeated measures models compared specific gravity-adjusted urinary methyl, propyl, and butyl paraben concentrations between samples “exposed” and “unexposed” to paraben-containing medication.ResultsEleven participants contributed 12 exposed and 45 unexposed samples, among which paraben concentrations did not differ. Use within 7 h was associated with 8.7-fold and 7.5-fold increases in mean methyl (P = 0.11) and propyl (P = 0.10) paraben concentrations, respectively, after adjusting for PCP use. However, these associations decreased to 1.3-fold (P = 0.76) and 2.6-fold (P = 0.34), respectively, after removal of one influential individual.ConclusionParaben-containing medications contributed to higher urinary paraben concentrations within hours of use.     

Allergic Contact Dermatitis to Condoms: Description of a Clinical Case and Analytical Review of Current Literature

We describe the case of a 42‐years‐old non‐atopic man who developed a severe eczematous reaction in the genital area some hours after the use of a condom (Settebello‐Hatù® Durex) containing a retarding cream. Patch test revealed a strong allergic reaction to the retarding cream and to benzocaine and paraben mix contained in the cream itself. Condoms with retarding cream should be avoided in man sensitized to local anestethetics.     

Endocrine disrupting chemicals associated with dry eye syndrome

BackgroundDry eye syndrome (DES) is a multifactorial disease that causes changes in the tear film and occurs more frequently in women. Sex hormones (SHs) influence tear production, and SHs imbalance is associated with DES. Endocrine-disrupting chemicals (EDCs) are compounds that can bind to SHs receptors, changing the SHs action in several organs and tissues.MethodsThe levels of 21 EDCs were measured in the urine of DES patients and healthy controls. All individuals were submitted to eye exams for DES and responded to the questionnaire “Ocular Surface Disease Index (OSDI)”. DES was considered present when the OSDI score was >20 and one of the DES tests surpassed the established thresholds.ResultsMethyl-protocatechuic acid (OHMeP), had higher urine levels in DES individuals than in control individuals (p = 0.0189). On the other hand, triclocarban (TCC) exhibited lower urine levels in DES individuals than in control individuals (p = 0.0081). Statistically significant positive associations were found between Methyl Paraben (MeP), EtP (ethyl paraben) and OHMeP with fluorescein staining test; between TCC and Tear breakup time test and between OHMeP and OSDI score. Significant negative associations were found between EtP and OHMeP and schirmer test; between OHMeP and Tear breakup time test; between TCC and the OSDI score and fluorescein and lissamine staining test.The quadratic discriminant function classified 94.4% of individuals in their groups based on the urine levels of EDCs.ConclusionThe following EDCs, MeP, EtP, and OHMeP, were associated with signs and symptoms of DES. TCC had a paradoxical protective effect against DES. These findings suggest that EDCs are associated with DES and the exposure should be included in the investigation of causes and risk factors for DES.     

A Review of the Endocrine Activity of Parabens and Implications for Potential Risks to Human Health

Parabens are a group of the alkyl esters of p-hydroxybenzoic acid and typically include methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben, isopropylparaben, and benzylparaben. Parabens (or their salts) are widely used as preservatives in cosmetics, toiletries, and pharmaceuticals due to their relatively low toxicity profile and a long history of safe use. Testing of parabens has revealed to varying degrees that individual paraben compounds have weakly estrogenic activity in some in vitro screening tests, such as ligand binding to the estrogen receptor, regulation of CAT gene expression, and proliferation of MCF-7 cells. Reported in vivo effects include increased uterine weight (i.e., butyl-, isobutyl-, and benzylparaben) and male reproductive-tract effects (i.e., butyl- and propylparaben). However, in relation to estrogen as a control during in vivo studies, the parabens with activity are many orders of magnitude less active than estrogen. While exposure to sufficient doses of exogenous estrogen can increase the risk of certain adverse effects, the presumption that similar risks might also result from exposure to endocrine-active chemicals (EACs) with far weaker activity is still speculative. In assessing the likelihood that exposure to weakly active EACs might be etiologically associated with adverse effects due to an endocrine-mediated mode of action, it is paramount to consider both the doses and the potency of such compounds in comparison with estrogen. In this review, a comparative approach involving both dose and potency is used to assess whether in utero or adult exposure to parabens might be associated with adverse effects mediated via an estrogen-modulating mode of action. In utilizing this approach, the paraben doses required to produce estrogenic effects in vivo are compared with the doses of either 17β-estradiol or diethylstilbestrol (DES) that are well established in their ability to affect endocrine activity. Where possible and appropriate, emphasis is placed on direct comparisons with human data with either 17β-estradiol or DES, since this does not require extrapolation from animal data with the uncertainties inherent in such comparisons. Based on these comparisons using worst-case assumptions pertaining to total daily exposures to parabens and dose/potency comparisons with both human and animal no-observed-effect levels (NOELs) and lowest-observed-effect levels (LOELs) for estrogen or DES, it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer. Additional analysis based on the concept of a hygiene-based margin of safety (HBMOS), a comparative approach for assessing the estrogen activities of weakly active EACs, demonstrates that worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring EACs in the diet such as the phytoestrogen daidzein.     

Association of nicotinamide with parabens: Effect on solubility, partition and transdermal permeation

Nicotinamide is a hydrophilic molecule, freely soluble in water, used as cosmetic active ingredient for its moisturizing and depigmenting properties. Moreover it has the ability to augment the solubility of poorly water-soluble molecules acting as a hydrotrope. The aim of this work was to study the effect of nicotinamide on the transdermal permeation of methyl, ethyl, propyl and butyl paraben. Parabens flux was measured in vitro in the presence and absence of different amounts of nicotinamide. From solubility studies it was found that nicotinamide forms one or more complexes with methyl, propyl and butyl paraben in water, even though with low stability constants. The interaction of ethyl paraben seems to be less easy to explain. The association of nicotinamide with parabens causes a significant reduction of the permeability coefficients of these preservatives through rabbit ear skin, caused by a reduction of the stratum corneum/vehicle partition coefficient. The effects of nicotinamide on parabens solubility, permeation and partitioning are potentially very interesting because nicotinamide can facilitate paraben dissolution in aqueous media (solutions, gels), reduce parabens partitioning in the oily phase thus guaranteeing an effective concentration in the water phase in emulsion and reduce transdermal penetration, thus reducing the toxicological risk.