The exploration of effect of terfenadine on Ca2+ signaling in renal tubular cells

Terfenadine, an antihistamine used for the treatment of allergic conditions, affected Ca²⁺-related physiological responses in various models. However, the effect of terfenadine on cytosolic free Ca²⁺ levels ([Ca²⁺]_i) and its related physiology in renal tubular cells is unknown. This study examined whether terfenadine altered Ca²⁺ signaling and caused cytotoxicity in Madin-Darby canine kidney (MDCK) renal tubular cells. The Ca²⁺-sensitive fluorescent dye fura-2 was used to measure [Ca²⁺]_i. Cell viability was measured by the fluorescent reagent 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay. Terfenadine at concentrations of 100-1000 μM induced [Ca²⁺]_i rises concentration dependently. The response was reduced by approximately 35% by removing extracellular Ca²⁺. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) partly inhibited terfenadine-evoked [Ca²⁺]_i rises. Conversely, treatment with terfenadine abolished BHQ-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited 95% of terfenadine-induced Ca²⁺ release. Terfenadine-induced Ca²⁺ entry was supported by Mn²⁺-caused quenching of fura-2 fluorescence. Terfenadine-induced Ca²⁺ entry was partly inhibited by an activator of protein kinase C (PKC), phorbol 12-myristate 13 acetate (PMA) and by three modulators of store-operated Ca²⁺ channels (nifedipine, econazole, and SKF96365). Terfenadine at 200-300 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in MDCK cells, terfenadine induced [Ca²⁺]_i rises by evoking PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Furthermore, terfenadine caused cell death that was not triggered by preceding [Ca²⁺]_i rises.

Drug interactions

Drugs for allergy are often taken in combination with other drugs, either to treat allergy or other conditions. In common with many pharmaceuticals, most such drugs are subject to metabolism by P450 enzymes and to transmembrane transport. This gives rise to considerable potential for drug-drug interactions, to which must be added consideration of drug-diet interactions. The potential for metabolism-based drug interactions is increasingly being taken into account during drug development, using a variety of in silico and in vitro approaches. Prediction of transporter-based interactions is not as advanced. The clinical importance of a drug interaction will depend upon a number of factors, and it is important to address concerns quantitatively, taking into account the therapeutic index of the compound.

Medications in pregnancy and lactation: Part 2. Drugs with minimal or unknown human teratogenic effect

This is the second of a two-part series on the use of medication during pregnancy and lactation. Pregnancy risk factors together with an increased incidence of chronic diseases and the rise in mean maternal age predict an increase in medication use during gestation. However, as highlighted in the first installment of this series, relatively few medications have specifically been tested for safety and efficacy during pregnancy, and, therefore, responses to those inquiries can be uninformed and inaccurate. Whereas the first installment provided new insight into the nature of medications with known human teratogenic effects, this part concentrates on drugs with minimal or no known human teratogenic effect. It is important that clinicians become familiar with all of the aspects of the drugs they prescribe, in addition to the controversies surrounding them, through consultation with maternal-fetal medicine specialists and through references and Web sites providing up-to-date information in an effort to promote safer prescribing practices.

Desloratadine: an update of its efficacy in the management of allergic disorders

Desloratadine (Clarinex, Neoclarityn, Aerius, Azomyr, Opulis, Allex), the principal metabolite of loratadine, is itself an orally active, nonsedating, peripheral histamine H(1)-receptor antagonist. It is indicated in the US and Europe for the treatment of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR) and chronic idiopathic urticaria (CIU). It has a rapid onset of effect, efficacy throughout a 24-hour dosage interval, and sustained efficacy in these allergic conditions, as demonstrated in placebo-controlled trials of up to 6 weeks' duration in adult and adolescent patients. At present, there are no published direct comparisons of desloratadine and other H(1)-antihistamines; however, the principal, potential clinical advantages of desloratadine over late-generation H(1)-antihistamines are the drug's decongestant activity, which has been corroborated in several studies of patients with allergic rhinitis, and its anti-inflammatory effects. Indeed, the decongestant activity of desloratadine did not differ from that of pseudoephedrine in a trial in patients with SAR, and in patients with SAR and coexisting asthma, desloratadine reduced asthma symptoms and beta(2)-agonist use, and improved forced expiratory flow in 1 second. However, these issues warrant further study. Desloratadine is generally well tolerated. The overall incidence of adverse events in adults, adolescents and children was not significantly different to that with placebo, and similar proportions of desloratadine or placebo recipients reported events such as pharyngitis, dry mouth, myalgia, somnolence, dysmenorrhoea or fatigue. Desloratadine does not cause sedation or prolong the corrected QT (QTc) interval, can be administered without regard to concurrent intake of food and grapefruit juice, and appears to have negligible potential for drug interactions mediated by several metabolic systems.

CONCLUSION

Although comparative studies with second-generation and other recently developed H(1)-antihistamines are needed to define the drug's clinical profile more clearly, desloratadine can be expected to claim a prominent place in the management of allergic disorders in general, and in the amelioration of specific symptoms of allergy (e.g. nasal congestion) in patients with such disorders.

Pharmacokinetic properties of single-dose loratadine and ambroxol alone and combined in tablet formulations in healthy men

BACKGROUND

Due to Mexico's complicated socioeconomic environment, causing a high occurrence of >1 person sharing a single room, respiratory conditions are spread easily. Respiratory conditions are the main reason for consultation with a physician. The most frequent symptoms are throat soreness and cough; therefore, a new formulation combining loratadine and ambroxol hydrochloride was designed to treat these 2 major symptoms. The combination is expected to provide relief when coprescribed with more specific therapies, such as antibiotics.

OBJECTIVE

This study determined the pharmacokinetic profile of single-dose loratadine-ambroxol hydrochloride combination therapy versus each component given separately. The analyses included descarboethoxyloratadine (DCL), the primary active metabolite of loratadine.

METHODS

This was a 4-week, single-center, randomized, open-label, 3-period crossover study in adult male volunteers aged 18 to 50 years and in good general health. Subjects were randomized to receive single doses of treatment A (2 loratadine 5-mg tablets + ambroxol 30-mg tablets), B (2 ambroxol 30-mg tablets), or C (1 loratadine 10-mg tablet) in 1 of 3 sequences (ABC, BCA, or CAB) per period. A 14-day washout period separated each treatment period. Plasma concentration-time data curves for each subject and treatment were analyzed by noncompart-mental methods to obtain values for area under the curve (AUC), maximum plasma concentration (C(max)), and time to reach C(max) (T(max)).

RESULTS

Thirty subjects (mean [SD] age, 22.5 [2.6] years) were enrolled. All treatments were well tolerated. Formulations A and C produced similar loratadine and DCL AUC from time 0 to 24 hours (AUC(0-24)) values, but showed slightly high C(max). values for loratadine and slightly low C(max) values for DCL, indicating failure to demonstrate bioinequivalence. Formulations A and B produced similar ambroxol C(max), T(max), and AUC(0-24) values.

CONCLUSIONS

In this population of healthy mate volunteers, results showed the bioavailability of loratadine and ambroxol from the new formulation and did not show impairment of absorption when the drugs were formulated in a combination tablet.

Pathophysiological role of leukotrienes in dermatological diseases: potential therapeutic implications

In vitro and in vivo data have demonstrated that leukotrienes play a key role not only in allergic airway diseases but also in inflammatory reactions of the skin. Antileukotriene drugs, i.e. leukotriene receptor antagonists and synthesis inhibitors, are a new class of anti-inflammatory drugs that have shown clinical efficacy in the management of asthma, allergic rhinitis and inflammatory bowel disease. To address the question of the validity and applicability of published evidence of the use of antileukotriene drugs in dermatological diseases, we reviewed data concerning the pathophysiological effect of leukotrienes in the skin and in skin diseases, and the experience with antileukotriene treatment that has been published. In vivo and in vitro data suggest that antileukotriene treatment may have efficacy in atopic dermatitis, different types of urticaria or psoriasis and other skin diseases such as bullous skin diseases, collagenoses, Sjogren-Larsson syndrome or Kawasaki disease. Nevertheless, published evidence is very limited and before any conclusions can be drawn, additional basic research needs to be performed with regard to the role of different leukotrienes and leukotriene receptors in skin diseases. On the basis of these data, randomised and placebo-controlled clinical trials with leukotriene antagonists and synthesis inhibitors should be performed. Moreover, future studies investigating the additive benefit of antileukotriene drugs are warranted, e.g. in combination with antihistamines, corticosteroids or other anti-inflammatory drugs.