Application Of Multiple Doses Research Articles

Topical skin penetration of diclofenac after single- and multiple-dose application

Transdermal penetration of nonsteroidal anti-inflammatory drugs (NSAIDs) has been shown to be highly variable. The present study was performed to gain insight into the transdermal penetration process of topically applied diclofenac and to test whether transdermal absorption leads to pharmacologically effective concentrations in dermal tissue layers beneath the application site. Six healthy male volunteers participated in this 2-way crossover study and were assigned to 2 treatment groups. In the first group, diclofenac was applied at a therapeutic dose of 60 mg/100 cm2 3 times daily for 4 days with subsequent occlusion with a plastic foil for 4 hours to enhance transdermal drug absorption. After a 1-week wash-out, diclofenac was applied at a single dose of 300 mg/100 cm2 without occlusion. Diclofenac in both groups was applied on a previously shaven area of the thigh. Transdermal penetration was assessed employing in vivo microdialysis. After multiple-dose administration mean diclofenac concentrations of 0.48 +/- 0.35 ng x ml(-1) were observed in subcutaneous tissue (mean +/- SEM). The mean AUC(subcutis/plasma) ratio of 0.08 +/- 0.02 indicates redistribution of diclofenac from the systemic circulation to the tissue. After single-dose treatment, mean tissue concentrations were 24.26 +/- 46.43 ng x ml(-1) with a mean AUC(subcutis/plasma) ratio of 60.85 +/- 57.59, which suggests direct tissue penetration of diclofenac. Transdermal penetration of diclofenac after multiple as well as after single application of the present formulation is highly variable. In addition to other factors influencing the transdermal penetration process, dose and mode of administration are important factors determining whether pharmacologically effective local tissue concentrations are attained.

Diclofenac metabolic profile following in vitro percutaneous absorption through viable human skin.

The extent of metabolism of diclofenac sodium in excised viable human skin was investigated using combination HPLC and radioactivity assay. In an earlier diffusion experiment using an in vitro flow-through diffusion system, radiolabelled diclofenac sodium in either lotion (Pennsaid) or aqueous solution was applied to viable human skin, either as single dose or multiple dose (8 times over 2 days). In this study, the receptor fluid samples from the diffusion experiment were subjected to extraction and the aliquot was analysed using HPLC to separate diclofenac and authentic metabolites. Based on the radioactivity of each HPLC fraction, the collection time of the fractions was compared with the retention time of diclofenac and metabolites in standard solutions. The samples from a single or multiple dose application of lotion showed radioactivity in mainly one fraction, whose retention time corresponded with diclofenac. Other HPLC fractions showed none or only small amounts of radioactivity within the error range of the assay. The same results were obtained with the pooled samples from the application of the lotion or of aqueous solution. The results suggest that diclofenac sodium does not undergo metabolism in viable human epidermis during percutaneous absorption in vitro. Hence, with topical application to human skin in vivo, diclofenac will be delivered with minimal, if any, metabolism.

O-124. Multiple-dose applications of the LHRH antagonist Cetrorelix (SB-75) in assisted reproduction according to the ‘Lübeck protocol’: the first steps

O-124. Multiple-dose applications of the LHRH antagonist Cetrorelix (SB-75) in assisted reproduction according to the ‘Lübeck protocol’: the first steps

Cholecystokinin activates area postrema neurons in rat brain slices.

Peripheral cholecystokinin (CCK) reduces food intake and triggers the secretion of both oxytocin and corticotropin-releasing hormone. These responses are partially initiated by activation of receptors in the peripheral endings of the vagus nerve. However, in vivo studies showing that after vagotomy systemic CCK induces fos activation of neurons in the area postrema (AP) suggest that circulating CCK may directly influence the activity of neurons in this structure. The present study was therefore designed to investigate the responsiveness of AP neurons to CCK using in vitro extracellular single-unit recording techniques. Bath application of 100 nM CCK for 200 s resulted in excitatory responses in 41% and inhibitory effects in 6% of 143 AP neurons tested. Application of multiple doses of CCK (1-100 nM) to single neurons demonstrated that CCK effects were dose dependent. The firing rate of tested neurons increased by 48 +/- 15% in response to 1 nM, by 89 +/- 22% in response to 10 nM, and by 242 +/- 77% in response to 100 nM CCK. After we blockaded synaptic transmission with a low-Ca2+/high-Mg2+ artificial cerebrospinal fluid, the excitatory effects of CCK remained in all nine neurons tested. The CCK-receptor antagonist L-364,718 had no significant effect on the responses to CCK (P > 0.1, n = 4), whereas, after perfusion of slices with the CCKB-receptor antagonist L-365,260, mean responses to CCK were significantly reduced to 12.6 +/- 4.7% of the control value (P < 0.001, n = 4). These results demonstrate a direct and dose-dependent excitatory action of CCK on AP neurons that is abolished by CCKB-receptor antagonists. These data emphasize the potential role of AP in processing afferent information derived from circulating peptide concentrations that could be involved in the regulation of food intake.

Ro 15-8081 in osteoarthritis of hip and knee: a double-blind placebo-controlled multicentre dose-ranging study on analgesia

Ro 15-8081, a substituted cyclohexanol hydrochloride, inhibits the re-uptake of norepinephrine and of serotonin. Its antinociceptive properties have been demonstrated in animals and then confirmed in humans after single-dose administration. The objective was to determine the analgesic efficacy and the safety of Ro 15-8081 in osteoarthritis of the hip and knee (femoro-tibial location) after multiple-dose application. The design for studying dosage employed 5 parallel groups in an international multicenter, double-blind, randomized trial having a duration of 2 weeks. Drugs studied were: 20 mg Ro 15-8081 (divided into 2 doses), 50 mg Ro 15-8081 (divided into 2 doses), 100 mg Ro 15-8081 (divided into 2 doses), placebo twice daily or 20 mg/day piroxicam (piroxicam in the morning and placebo in the evening). Piroxicam was used as a reference drug in order to validate clinical testing. Assessment criteria were pain (100-mm VAS) and function (Lequesne's index). A responder (main assessment criterion) was defined as a patient exhibiting a reduction of at least 30% of pain (VAS) during the study (intention-to-treat analysis). A total of 522 patients were enrolled in the study. A clear beneficial effect of piroxicam was observed when compared with placebo (70% and 48% of responders in piroxicam and placebo groups respectively; P < 0.0001). Multigroup comparison showed a statistically significant difference between Ro 15-8081 groups and the placebo group regarding mean change in pain between D 1 and D end and the rate of VAS responders. Comparison (Dunnett's t or χ 2 tests) between each individual Ro 15-8081 and the placebo group reached statistical significance for the 100 mg Ro 15-8081 group (mean change in pain between D 1 and D end: P = 0.05; percentage of responders: P = 0.0008) but no statistically significant difference for the other dosages of Ro 15-8081. Fifty-three patients withdrew from the study because of adverse events and/or inefficacy, mainly in 50 and 100 mg Ro 15-8081 groups and in a dose-related manner. The adverse events which appeared to be drug related were mainly dryness of the mouth, insomnia, headache, constipation, nausea, dizziness, nervousness, palpitation. This study suggests that 100 mg Ro 15-8081 per day divided into 2 doses has (1) an analgesic effect in hip or knee osteoarthritis and (2) poor acceptability in the conditions of the study regimen application.

Piroxicam Plasma Concentrations Following Repeated Topical Application of a Piroxicam 0.5% Gel

The pharmacokinetic parameters of a piroxicam 0.5% topical gel were determined in 20 healthy volunteers (6 women and 14 men) following application of multiple doses (20mg piroxicam daily) over 14 days. 21 blood samples were drawn from each patient beginning just before application of the first dose, with the final sample taken 14 days after application of the last dose. Plasma concentrations of piroxicam were determined by high-performance liquid chromatography using UV detection at 340nm. There was considerable interindividual variation in piroxicam half-lives with a mean of 79 hours. Mean piroxicam plasma concentrations at steady-state were between 300 and 400 ng/ml, which is about 5% of those observed after equivalent doses of oral or intramuscular piroxicam. No adverse experiences were reported during the study period. Thus, the results of this study confirm the minimal systemic absorption of piroxicam during multiple-dose application of the 0.5% topical gel and the excellent tolerability of this mode of piroxicam therapy.

Somesthetic and Electrophysiologic Effects of Topical 0.025% Capsaicin in Man

As a topical agent, capsaicin reportedly blocks pain without otherwise impairing sensation. Ten subjects underwent blinded, multiple-dose application of topical 0.025% capsaicin or control emollient to skin test sites in order to evaluate capsaicin effectiveness and toxicity. Clinical changes in somesthetic perception of pinprick, heat and cold developed, but neurogenic flare responses were unchanged. Clinical and electrophysiologic measures of large fiber and autonomic function were unaffected by capsaicin. This study indicates that 0.025% capsaicin is a safe topical agent with demonstrable clinical effects on small fiber function but not on large fiber or autonomic function.

Somesthetic and electrophysiologic effects of topical 0.025% capsaicin in man.

As a topical agent, capsaicin reportedly blocks pain without otherwise impairing sensation. Ten subjects underwent blinded, multiple-dose application of topical 0.025% capsaicin or control emollient to skin test sites in order to evaluate capsaicin effectiveness and toxicity. Clinical changes in somesthetic perception of pinprick, heat and cold developed, but neurogenic flare responses were unchanged. Clinical and electrophysiologic measures of large fiber and autonomic function were unaffected by capsaicin. This study indicates that 0.025% capsaicin is a safe topical agent with demonstrable clinical effects on small fiber function but not on large fiber or autonomic function.

Characterization of the induction of ornithine decarboxylase activity by benzoyl peroxide in SENCAR mouse epidermis.

The induction of epidermal ornithine decarboxylase (ODC) activity by benzoyl peroxide (BPO) was characterized to evaluate the usefulness of this effect as a short-term marker of BPO-induced mouse skin tumor promotion. The maximal induced levels of ODC specific activity, after a single topical dose of BPO, were greater than 2-fold higher when a cold scraping method was used to prepare epidermis rather than the commonly used heat treatment method. Therefore, the cold scraping method was used for all the work reported here. Application of a single 20 mg dose of BPO to the dorsal skin of SENCAR mice caused a relatively small induction of epidermal ODC activity, to a level less than 1/40 that induced by a single 2 micrograms dose of 12-O-tetradecanoylphorbol-13-acetate (TPA). Furthermore, the time-courses of induction were different after single doses of TPA and BPO, with peak activities observed at approximately 6 and approximately 24 h after treatment respectively. In contrast, after a total of five 20 mg doses of BPO were topically applied (one dose every 2 days), ODC activity was transiently induced to an average level greater than 15 times after a single dose. Additionally, on this dosing regimen, the peak of ODC activity shifted to approximately 4 h after the last treatment, so that the time-course of ODC induction resembled that after multiple applications of TPA. The extent of epidermal ODC induction by BPO was found to be a complex function of the frequency of dosing and the number of treatments. However, when BPO treatments were administered from 1 to 7 days apart, similar maximal induced levels of ODC activity were eventually achieved after application of multiple doses. Importantly, the dose-response for the induction of ODC activity by five doses of BPO (applied one dose every 2 days) was highly correlated with published data on the dose-response for tumor promotion by this organic peroxide, indicating that ODC induction is a good short-term marker of BPO-induced tumor promotion in SENCAR mice.

In vitro and in vivo studies of streptomycin-dependent cholera vibrios.

Streptomycin-dependent cholera vibrio strains were derived from Inaba, Ogawa, and NAG vibrios by the method of Mel. These phenotypes grew more slowly and attacked fermentable substances after a longer period of time than the streptomycin-sensitive parent strains. Rabbits injected with streptomycin-sensitive strains and their streptomycin-dependent forms showed homologous agglutinin production. Patas monkeys fed with 10(9) streptomycin-dependent strains shed them for 1 to 2 days without ill effect, whereas the same number of streptomycin-independent organisms caused disease. The possibility of the application of multiple doses of streptomycin-dependent organisms in oral immunization against cholera was considered.

In Vitro and In Vivo Studies of Streptomycin-Dependent Cholera Vibrios

Streptomycin-dependent cholera vibrio strains were derived from Inaba, Ogawa, and NAG vibrios by the method of Mel. These phenotypes grew more slowly and attacked fermentable substances after a longer period of time than the streptomycin-sensitive parent strains. Rabbits injected with streptomycin-sensitive strains and their streptomycin-dependent forms showed homologous agglutinin production. Patas monkeys fed with 10(9) streptomycin-dependent strains shed them for 1 to 2 days without ill effect, whereas the same number of streptomycin-independent organisms caused disease. The possibility of the application of multiple doses of streptomycin-dependent organisms in oral immunization against cholera was considered.