Pharmacokinetic and pharmacodynamic profiles of sumatriptan in migraine patients with headache recurrence or no response

Evaluation of sex differences in the pharmacokinetics of oral sumatriptan in healthy Korean subjects using population pharmacokinetic modeling

Sumatriptan was introduced in 1983, as the first of the triptans, selective 5‐hydroxytryptamine (5‐HT_1B/1D) receptor agonists, to treat moderate to severe migraine. Migraine predominates in females. Although there have been reports of sex differences in migraine‐associated features and pharmacokinetics (PKs) of some triptans, sex differences in the PKs of oral sumatriptan have never been evaluated in Korean. We conducted this study of oral sumatriptan to assess the sex differences in Korean population. Thirty‐eight healthy Korean subjects who participated in two separate clinical studies receiving a single oral dose of 50 mg sumatriptan with the same protocols were included in this analysis. A total of 532 sumatriptan concentration observations were used for a population PK modeling. Validation of final population PK model of sumatriptan was performed using bootstrap and visual predictive check. The PK profile of oral sumatriptan was adequately described by a one‐compartmental model with combined transit compartment model and a first‐order absorption. The covariate analysis showed that the clearance of oral sumatriptan was significantly higher in males than in females (male: 444 L/h, female: 281 L/h). Our results showed that there were sex differences in the clearance of oral sumatriptan. These results encourage further studies to establish the sumatriptan pharmacokinetic–pharmacodynamic model considering sex‐related PK differences, which may help to determine optimal dosing regimens for effective treatment of migraine in males and females. Clinical trial registration: CRIS Registration No. KCT0001784.

Is selective 5-HT1F receptor agonism an entity apart from that of the triptans in antimigraine therapy?

Migraine is a neurovascular disorder that involves activation of the trigeminovascular system and cranial vasodilation mediated by release of calcitonin gene-related peptide (CGRP). The gold standard for acute migraine treatment are the triptans, 5-HT1B/1D/(1F) receptor agonists. Their actions are thought to be mediated through activation of: (i) 5-HT1B receptors in cranial blood vessels with subsequent cranial vasoconstriction; (ii) prejunctional 5-HT1D receptors on trigeminal fibers that inhibit trigeminal CGRP release; and (iii) 5-HT1B/1D/1F receptors in central nervous system involved in (anti)nociceptive modulation. Unfortunately, coronary arteries also express 5-HT1B receptors whose activation would produce coronary vasoconstriction; hence, triptans are contraindicated in patients with cardiovascular disease. In addition, since migraineurs have an increased cardiovascular risk, it is important to develop antimigraine drugs devoid of vascular (side) effects. Ditans, here defined as selective 5-HT1F receptor agonists, were developed on the basis that most of the triptans activate trigeminal 5-HT1F receptors, which may explain part of the triptans' antimigraine action. Amongst the ditans, lasmiditan: (i) fails to constrict human coronary arteries; and (ii) is effective for the acute treatment of migraine in preliminary Phase III clinical trials. Admittedly, the exact site of action is still unknown, but lasmiditan possess a high lipophilicity, which suggests a direct action on the central descending antinociceptive pathways. Furthermore, since 5-HT1F receptors are located on trigeminal fibers, they could modulate CGRP release. This review will be particularly focussed on the similarities and differences between the triptans and the ditans, their proposed sites of action, side effects and their cardiovascular risk profile.

Prediction of Headache Response in Migraine Treatment

Triptans are efficacious for the acute treatment of migraine attacks. Yet, defining a concentration-effect relation for these compounds is difficult as the dynamics of the migraine attack are not thoroughly understood. The objective of this investigation was to develop a disease model to predict measures of headache in randomized placebo-controlled clinical trials investigating oral sumatriptan as a paradigm compound. A hidden Markov model based on the states of response (no relief, relief, and pain free) and headache scores (observed variable) was used in conjunction with population pharmacokinetics. Model parameters were capable of predicting the course of headache relief, pain-free status and headache recurrence. It was shown that sumatriptan shortens mean transit times between states by up to 5 h. The potency of sumatriptan (EC50) was 9 ng/ml. These findings demonstrate the value of combining pharmacokinetic and efficacy information to model disease and characterize time-independent drug properties in a population of migraineurs.

Migraine recurrence is not associated with depressive or anxiety symptoms. Results of a randomized controlled trial

In order to investigate the plausible association of migraine recurrence with anxiety and depressive symptoms, a multicentre, randomized, double-blind, placebo-controlled, crossover clinical trial was conducted using sumatriptan as a vehicle drug. Migraineurs were randomly assigned to receive either 50 mg sumatriptan or placebo for three consecutive migraine attacks, and then cross over to the other treatment for three more migraine attacks. The primary measurements were the observed rate of migraine recurrence in relation to (i) patient's mood condition, measured by the Hamilton rating scales for depression and anxiety and (ii) patient's general health and functioning measured by the Symptom Checklist (SCL)-90-R. Migraine recurrence was defined as any migrainous headache that occurred within 24 h post treatment, only when pain free at 2 h was achieved. The analysis of efficacy was performed on 376 migraine attacks treated with sumatriptan and 373 attacks treated with placebo. Recurrence ratio was 14.1% and 5.1%, respectively ( P = 0.045). The number needed to treat for pain free at 2 h post dose was 5.4. Recurrence was not affected by Hamilton scores for depression or anxiety, SCL-90-R scores or treatment. Apparently, depressive or anxiety symptoms do not influence headache recurrence in acute pharmaceutical migraine treatment, but further investigation is required.

What can be learned from the history of recurrence in migraine? A comment

Recurrence was first recognised as a clinical problem in 1989 with the advent of sumatriptan. The history of recurrence in early sumatriptan randomised clinical trials is described. Recurrence has been ascribed to patient-dependent factors but experience with ergot alkaloids suggested that recurrence can also be treatment-dependent. Possible mechanisms for recurrence are discussed.

Analysis of the relationship between age and treatment response in migraine

In migraine, headache severity varies with age. As a consequence, the effectiveness of medication may also depend on a patient's age. The purpose of this study was to assess the combined effect of age and drug treatment on headache characteristics. Using data from clinical trials of sumatriptan in adolescents and adults, we show how the interaction between age and drug exposure can be parameterised as a covariate on a Markov model that describes the decline of headache severity over three clinically defined stages (no relief, relief and pain-free status). The model explains important clinical observations: (i) the rates at which the pain relief and pain-free status were attained were found to be inversely related to age; (ii) in placebo-treated patients, the mean transit time from 'no relief' to 'relief' is 3 h for young adolescents and increases to 6 h for patients aged >or= 30 years; and (iii) sumatriptan reduces the transit time to 2 h, irrespective of age. These findings indicate that the therapeutic gain over placebo increases with age. Prospective studies of antimigraine drugs should take this relationship into account when extrapolating efficacy data from adults to adolescents.

Development and Validation of a HPTLC Method for the Estimation of Sumatriptan in Tablet Dosage Forms

A simple, precise, accurate and rapid high performance thin layer chromatographic method has been developed and validated for the estimation of sumatriptan in tablet dosage forms. The stationary phase used was precoated silica gel 60F254. The mobile phase used was a mixture of methanol:water:glacial acetic acid (4.0:8.0:0.1, v/v/v). The detection of spots was carried out at 230 nm. The method was validated in terms of linearity, accuracy, precision and specificity. The calibration curve was found to be linear between 200 to 800 ng/spot. The limit of detection and the limit of quantification for the sumatriptan were found to be 63.87 and 193.54 ng/spot, respectively. The proposed method can be successfully used to determine the drug content of marketed formulation.

Pathways to the Best Fit of Triptans for Migraine Patients

Variability in drug response is a major barrier to the successful treatment of migraine, and most treatments are only optimal in a subset of patients. Although triptans provide the best therapeutic option for the treatment of acute migraine, it has not previously been possible to predict how well patients will respond to a specific triptan or whether they will experience unpleasant adverse events. Hence, it has been difficult for physicians to match individual patients with the most suitable agent to treat their migraine pain. Intrapatient variability has been associated with polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters and drug targets. Pharmacogenetics provides the possibility of tailoring the therapeutic approach to individual patients, in order to maximize treatment efficacy while minimizing the potential for unwanted side-effects. This review demonstrates how almotriptan may overcome genetically determined responses by utilizing diverse metabolic pathways to provide therapeutic benefit to many migraineurs.

Parenteral vs. oral sumatriptan and naratriptan: plasma levels and efficacy in migraine. a comment

The clinical efficacy in migraine was compared for oral and subcutaneous sumatriptan and naratriptan. Doses of the two administration forms were chosen as resulting in comparable blood concentrations. Subcutaneous administrations of the drugs were superior for efficacy than the oral forms. This most likely due to a quicker rise in blood concentrations after subcutaneous injections.. In designing new therapies for migraine one should aim at a quick absorption of the drug, which will probably result in an increased efficacy.

The phe-124-Cys and A-161T variants of the human 5-HT1B receptor gene are not major determinants of the clinical response to sumatriptan

BACKGROUND

The 5-HT(1B/1D) receptor agonist sumatriptan is highly effective in the treatment of migraine. However, some patients do not respond to sumatriptan or experience recurrence of the headache after initial relief. In addition, some patients report chest symptoms after the use of sumatriptan.

OBJECTIVE

To assess whether 2 genetic variants (F124C changing a phenylalanine for a cysteine and polymorphism A/T at nucleotide position -161 in the 5' regulatory region) of the 5-HT(1B) receptor play a major role in the therapeutic response to sumatriptan. The 5-HT(1B) receptor most likely mediates the therapeutic action and coronary side effects of sumatriptan, and both F124C and A-161T have relevant functional consequences on either the affinity of sumatriptan to bind to the 5-HT(1B) receptor or on receptor expression level itself, respectively.

METHOD

Genomic DNA of a relatively small but very well-characterized set of migraine patients with consistently good response to sumatriptan (n = 14), with no response (n = 12), with recurrence of the headache (n = 12), with chest symptoms (n = 13), and patients without chest symptoms (n = 27) was available for the genetic analyses and screened for the F124C variant and the A-161T polymorphism in the human 5-HT(1B) receptor gene.

RESULTS

F124C was not detected in any of the patients studied. In addition, we did not observe drastic changes in allele frequencies of the A-161T polymorphism that might hint to a causal relation with the therapeutic effect of sumatriptan.

CONCLUSION

We have not obtained any evidence that variants F124C and A-161T of the 5-HT(1B) receptor are major determinants in the clinical response to sumatriptan.

Association study between clinical response to rizatriptan and some candidate genes

The aim of this study was to test genetic differences in the clinical response to rizatriptan in patients affected by migraine without aura. These genetic differences could be explained by various genes, the HTR1B, encoding the 5-HT₁ receptor subtype, MAOA gene that encodes the monoamino-oxidase, the main metabolic enzyme of this triptan, SLC6A4 (gene encoding the serotonin transporter) and DRD₂ (gene encoding the D₂ receptor), both involved in the pathogenesis of migraine. Fifty unrelated patients affected by migraine without aura (IHS) were included. Patients were divided into two groups (responders and non-responders) according to clinical response. Thirty-one out of fifty patients responded to rizatriptan. A significant difference among the two groups was observed in both allele (p=0.02) and genotype distribution (p=0.03) of DRD2/NcoI. The significant association with the DRD2/NcoI polymorphism in responders suggested that the DRD2/NcoI C allele may be considered a susceptibility factor heralding a good response to rizatriptan.

Chiropractic management of a patient with migraine headache

OBJECTIVE

To describe the use of chiropractic care for a patient with migraine headache.

CLINICAL FEATURES

A patient suffered from migraine headaches after an automobile accident. Neck disability scores, visual analog score, and algometry scores were used to track patient progress.

INTERVENTION AND OUTCOME

The patient's range of motion, flexibility, and strength improved following a regimen of spinal manipulation and active and passive therapeutic care. After 12 weeks of treatment, the duration, frequency, and intensity of her migraines decreased.

CONCLUSION

This case offers an example of the potential effects of chiropractic and rehabilitative treatment for migraine headache sufferers.

Pharmacokinetic studies in migraine: What questions should physicians ask?

Migraine is a benign self-limiting condition for which the objective of treatment is to maximize the patient's quality of life by reducing the frequency of attacks and attenuating the pain and suffering of an individual attack as quickly and safely as possible. Evaluating the efficacy of antimigraine treatments, particularly those for the management of the acute attack, is relatively easy because acute symptomatic benefit is the criterion of success. For prophylaxis, therapeutic success generally is measured by relatively simple parameters such as attack frequency. Given that the clinical response to antimigraine therapies relatively is readily assessed by history, the role of more sophisticated investigations such as pharmacokinetic studies may not be immediately clear. This paper aims to provide clinicians with a guide to interpretation of such studies.

Migraine prophylactic medication usage patterns in The Netherlands

This study aims to investigate usage patterns of specific migraine prophylactic medications in ergotamine and triptan patients commencing this treatment for the first time during 1 January 1992 until 31 December 1998. Usage patterns of specific migraine prophylactic drugs were evaluated for each patient by accessing data from a large prescription database and were characterized as continued, switch or stop use during the patient observation period. Several patient and medication-related factors were explored in order to identify a possible relationship with the specific usage pattern defined. Approximately 75% of the study population (n = 729) had terminated (stop or switch) prophylactic treatment after 1 year. Age < 40 years (relative risk (RR) 1.9; 95% confidence interval (CI) 1.2-3.2) and the concomitant use of non-steroidal anti-inflammatory drugs (RR 3.2; 95% CI 1.2-5.5) or specific abortive migraine drugs resulted in a faster onset of treatment modification (switch). Overall, migraine prophylactic treatment is used for a relatively short period, probably attributable to the common limitations associated with migraine prophylaxis, such as poor compliance and/or limited therapeutic efficacy. Patterns of use can be influenced by a variety of factors, including age, type of prescriber and certain co-medication. Patient interview studies are required to clarify these issues further.

Triptans (serotonin, 5-HT1B/1D agonists) in migraine: detailed results and methods of a meta-analysis of 53 trials

The triptans, selective serotonin 5-HT1B/1D agonists, are very effective acute migraine drugs. Soon, seven different triptans will be clinically available at 13 different oral doses, making evidence-based selection guidelines necessary. Triptan trials have similar designs, facilitating meta-analysis. We wished to provide an evidence-based foundation for using triptans in clinical practice, and to review the methodological issues surrounding triptan trials. We asked pharmaceutical companies and the principal investigators of company-independent trials for the 'raw patient data' of all double-blind, randomized, controlled, clinical trials with oral triptans in migraine. All data were cross-checked with published or presented data. We calculated summary estimates across studies for important efficacy and tolerability parameters, and compared these with those from direct, head-to-head, comparator trials. Out of 76 eligible clinical trials, 53 (12 not yet published) involving 24089 patients met the criteria for inclusion. Mean results (and 95% confidence intervals) for sumatriptan 100 mg, the first available and most widely prescribed oral triptan, are 59% (57-60) for 2 h headache response (improvement from moderate or severe to mild or no pain); 29% (27-30) for 2 h pain free (improvement to no pain); 20% (18-21) for sustained pain free (pain free by 2 h and no headache recurrence or use of rescue medication 2-24 h post-dose), and 67% (63-70) for consistency (response in at least two out of three treated attacks); placebo-subtracted proportions for patients with at least one adverse event (AE) are 13% (8-18), for at least one central nervous system AE 6% (3-9), and for at least one chest AE 1.9% (1.0-2.7). Compared with these data: rizatriptan 10 mg shows better efficacy and consistency, and similar tolerability; eletriptan 80 mg shows better efficacy, similar consistency, but lower tolerability; almotriptan 12.5 mg shows similar efficacy at 2 h but better sustained pain-free response, consistency, and tolerability; sumatriptan 25 mg, naratriptan 2.5 mg and eletriptan 20 mg show lower efficacy and better tolerability; zolmitriptan 2.5 mg and 5 mg, eletriptan 40 mg, and rizatriptan 5 mg show very similar results. The results of the 22 trials that directly compared triptans show the same overall pattern. We received no data on frovatriptan, but publicly available data suggest substantially lower efficacy. The major methodological issues involve the choice of the primary endpoint, consistency over multiple attacks, how to evaluate headache recurrence, use of placebo-subtracted proportions to control for across-study differences, and the difference between tolerability and safety. In addition, there are a number of methodological issues specific for direct comparator trials, including encapsulation and patient selection. At marketed doses, all oral triptans are effective and well tolerated. Differences among them are in general relatively small, but clinically relevant for individual patients. Rizatriptan 10 mg, eletriptan 80 mg and almotriptan 12.5 mg provide the highest likelihood of consistent success. Sumatriptan features the longest clinical experience and the widest range of formulations. All triptans are contra-indicated in the presence of cardiovascular disease.

Headache Recurrence and Treatment

The definition of recurrence includes the following: any headache occurring after a headache-free state at 2 hours and within 24 hours after intake of drug; a headache that has never been studied systematically; a headache that may not be an outcome of drug treatment; a headache that may be due to the inherent nature of migraine and individual patient characteristics such as duration of attack; and headache for which effective treatment may be a re-dose of the initial medication or addition of steroidal or nonsteroidal anti-inflammatory medications.

Sumatriptan responsiveness and clinical, psychiatric and psychologic features in migraine patients

OBJECTIVE

To compare sumatriptan responders and nonresponders in a migraine population with regard to a number of clinical, psychiatric and psychologic features.

METHODS

Patients were drawn from a referral headache clinic population, and classified as responders or nonresponders. Clinical features were assessed by a written questionnaire. The lifetime prevalence of several psychiatric disorders was determined by the National Institute of Mental Health diagnostic interview schedule and personality factors were measured by the 16 Personality Factors (16PF) Questionnaire.

RESULTS

Nonresponders indicated less influence on their migraine by menstrual factors, had a higher lifetime prevalence of generalized anxiety, and showed 16PF scores indicating greater shyness, self-sufficiency and perfectionism. Nonresponders were also more imaginative and less socially outgoing.

CONCLUSION

Although they must be interpreted with caution due to small sample size and the multiple comparisons made, our results indicate that there may be differences between sumatriptan responders and nonresponders with regard to a number of clinical, psychiatric and psychologic factors. These results suggest that biological differences exist between the two patient groups which likely account for both the differences in their responses to sumatriptan and in the clinical features noted above.

Chronopharmacokinetics of sumatriptan in healthy human subjects

Rhythms in the onset and symptoms of several diseases are well established. Migraine is a disorder that exhibits periodicity in its symptoms and so chronotherapy may be beneficial in treating the problem. Designing a chronotherapeutic schedule requires chronopharmacokinetic and chronopharmacodynamic data of the drugs prescribed. We have studied the chronopharmacokinetics of sumatriptan, a drug of choice in migraine treatment. Twelve healthy male volunteers were treated with 100 mg sumatriptan orally at 0700, 1300, 1900 and 0100 h in a randomized 4 x 4 Latin square crossover design, with a wash-out period of one week. Serum samples were analysed by high performance liquid chromatography with an electrochemical detector. Pharmacokinetic parameters were calculated using noncompartmental methods. The pharmacokinetic parameters were analysed using analysis of variance and a two-tailed paired t-test at the probability of 95%. The mean peak serum concentration following the 0700 h administration (Cmax; 59.09 +/- 10.53 ng mL(-1)) was significantly (P < 0.05; n = 12) higher than after the 1900 h administration (Cmax 41.88 +/- 12.21 ngmL(-1)). The mean area under the serum concentration-time curve from time zero to the last time-point (AUCo-t), the area under the serum concentration-time curve from zero to infinity (AUC 0-infinity), and the area under the first moment curve (AUMC) were significantly (P < 0.05; n = 12) higher following the 0700 and 0100 h administrations than after the 1900 h administration. Following administration at 0700 h, the mean oral clearance (CLs/f; 781 +/- 186 mL h(- 1) kg(-1)) and the apparent volume of distribution (Vd/f; 2,379 +/- 684) were significantly lower (P < 0.05; n = 12) than after the 1900 h administration (CLs/f 1,208 +/- 458 mL h(-1) kg(-1), Vd/f 4,655 +/- 2,096 mL kg(-1)). The mean Vd/f value was again lower after the 1300h administration than after the 1900 h administration (2,763 +/- 1,417 vs 4,655 +/- 2,096 mL kg(-1); P < 0.05; n = 12). The variations may be due to the time dependent changes in the extent of absorption and/or circadian variations in hepatic blood flow.

5-Alkyltryptamine derivatives as highly selective and potent 5-HT1D receptor agonists

A series of 5-alkyltryptamines (6) and the corresponding conformationally constrained analogues (8) have been synthesized. The structure activity relationships (SAR) at the 5-position of the indole skeleton and the ethylamine side chain have been studied. Functional activities were assessed using isolated rabbit saphenous vein. Potent, selective ligands were found (6e, Ki 2.5 nM, 5-HT1B/5-HT1D 125-fold) that have potential for treating acute migraine.

Use and overuse of sumatriptan. Pharmacoepidemiological studies based on prescription register and interview data

The serotonin agonist sumatriptan was marketed in Denmark in 1992 for the treatment of acute attacks of migraine and cluster headache. The clinical development program of the drug was impressive. However, knowledge of the long-term use of sumatriptan in unselected patients was lacking. Misuse of sumatriptan was reported in single patients shortly after the introduction of the drug. The aim of the present thesis was, therefore, to provide an epidemiological description of sumatriptan use with particular emphasis on overuse. The author conducted three studies, two of which were exclusively based on population-based data from a regional (Odense Pharmacoepidemiological Database) and a national (Registry of Drug Statistics, Danish Medicines Agency) prescription registry. Both registries record patient-specific information, thus enabling the conduct of longitudinal studies of drug use. The regional registry covers the county of Funen (reimbursable prescription drugs only), while the national registry records information on all prescriptions presented in the entire country. Consumption was described by means of the Defined Daily Dose (DDD) unit. One DDD of sumatriptan amounts to 100 mg orally or 6 mg subcutaneously. Subjects were classified as recipients of single or multiple prescriptions. Individuals in the latter category were characterized by the 30-day period with the most intensive dispensing of sumatriptan (peak use): low (less than 30 DDD/30 days), intermediate (30-59 DDD/30 days) and high-peak users (60 or more DDD/30 days). In 1995, 33,206 users of sumatriptan were identified in Denmark, corresponding to a 1-year period prevalence of use of 7.8 per 1,000 inhabitants (only persons aged > or = 16 years were included). A female-to-male ratio of 3.8:1 was found. Use was most common among women aged 35-54 years and was highest among 45 to 49-year-olds for both sexes. The standardized period prevalence of sumatriptan use varied regionally between the Danish counties from 6.4 to 9.6 per 1,000 inhabitants. The period prevalence of sumatriptan use in the county of Funen was highly comparable with that of the entire nation. Among the 43,389 sumatriptan users presenting prescriptions for sumatriptan in Denmark in 1994 and 1995, 507 (1.1%) and 1726 (4.0%) belonged to the high and intermediate-peak-use group, respectively. Patients belonging to these two groups were responsible for 38% of the total consumption of sumatriptan. For patients in the high-peak-use group the median span between first and last prescription was 693 days while the median quantity of sumatriptan purchased was 648 DDD. Highly comparable patterns of long-term intense sumatriptan use were found in the data from the regional registry, which covered the 27-month period after the introduction of the drug (February 1992). The register data were highly suggestive of overuse, but lacked essential information, e.g., the indication for use. A third study was therefore conducted using a combination of register and interview data. During a 14-day period, current users of sumatriptan were recruited through community pharmacies in the county of Funen. Respondents returned a signed consent form, including their unique personal identification number (CPR), allowing us to retrieve patient-specific data from the regional registry. For each respondent, all available relevant prescription data for the period 1992-96 were retrieved. Subjects were classified into high, intermediate, and low-peak-use groups according to register data from the 4-year period. The register data were used to evaluate representativity after anonymizing nonrespondent data. The response rates were 33% (7/21) in the high-peak-use group, 47% (30/64) in the intermediate-peak-use group, and 56% (196/350) in the low-peak-use group. Respondents and nonrespondents in the three groups were comparable with regard to age and use of other drugs. (ABSTRACT TRUNCATED)

Pharmacokinetic profile of alniditan nasal spray during and outside migraine attacks

AIMS

To compare the pharmacokinetic profile of intranasal alniditan during and outside migraine attacks, and to investigate the relationship between initial rise of alniditan plasma concentration, and headache improvement.

METHODS

Twenty-seven migraine patients (age: 18-65 years) were randomized to receive alniditan 2 mg or 4 mg, and investigated both during and outside a migraine attack. Maximal plasma concentrations (Cmax), time to Cmax (tmax), and the area under the curve over 2 h (AUC(0,2 h)), were calculated from the individual plasma concentration-time profile, obtained from 10 blood samples in each patient, during each of the two administrations.

RESULTS

Alniditan was rapidly absorbed into the systemic circulation (tmax=11 min). All investigated pharmacokinetic parameters (Cmax, tmax, AUC(0,2 h)) were similar during and outside migraine attacks, both in the 2 mg (n = 13) and the 4 mg group (n = 14). In the 4 mg group, during attacks, mean plasma alniditan concentration at 5 min after administration (Ct=5) in responders (21+/-16 ng ml(-1); n=10) was significantly higher than the Ct=5 in nonresponders (3+/-3 ng ml(-1); P=0.01; n=4). However, the Cmax and AUC(0,2 h) in responders (33+/-18 ng ml(-1) and 12+/-6 ng ml(-1) h) were also significantly higher than the Cmax and AUC(0,2 h) in nonresponders (13+/-9 ng ml(-1); P=0.048 and 5+/-3 ng ml(-1) h; P=0.03).

CONCLUSIONS

Absorption of alniditan nasal spray was not affected by migraine attacks, although 95% confidence intervals were wide. Early rise of plasma concentrations and the amount of drug in the circulation were related to headache improvement in the higher dose group.

Human variability and noncancer risk assessment- An analysis of the default uncertainty factor

A 10-fold uncertainty factor is used for noncancer risk assessments to allow for possible interindividual differences between humans in the fate of the chemical in the body (kinetics) and target organ sensitivity (dynamics). Analysis of a database on the variability in each of these aspects is consistent with an even subdivision of the 10-fold factor into 10(0.5) (3.16) for kinetics and 10(0.5) (3.16) for dynamics. Analysis of the number of subjects in a normally and log-normally distributed population which would not be covered by factors of 3.16 supports this subdivision and also the use of a 10-fold factor to allow for both aspects. Analysis of kinetic data for subgroups of the population indicates that the standard default value of 3.16 for kinetics will not be adequate for all routes of elimination and all groups of the population. A scheme is proposed which would allow the selection of appropriate default uncertainty factors based on knowledge of the biological fate and effects of the chemical under review. Copyright 1998 Academic Press.