Interaction between ketoconazole and almotriptan in healthy volunteers

Predictive Models for Human Cytochrome P450 3A7 Selective Inhibitors and Substrates

Inappropriate use of prescription drugs is potentially more harmful in fetuses/neonates than in adults. Cytochrome P450 (CYP) 3A subfamily undergoes developmental changes in expression, such as a transition from CYP3A7 to CYP3A4 shortly after birth, which provides a potential way to distinguish medication effects on fetuses/neonates and adults. The purpose of this study was to build first-in-class predictive models for both inhibitors and substrates of CYP3A7/CYP3A4 using chemical structure analysis. Three metrics were used to evaluate model performance: area under the receiver operating characteristic curve (AUC-ROC), balanced accuracy (BA), and Matthews correlation coefficient (MCC). The performance varied for each CYP3A7/CYP3A4 inhibitor/substrate model depending on the data set type, model type, rebalancing method, and specific feature set. For the active inhibitor/substrate data set, the optimal models achieved AUC-ROC values ranging from 0.77 ± 0.01 to 0.84 ± 0.01. For the selective inhibitor/substrate data set, the optimal models achieved AUC-ROC values ranging from 0.72 ± 0.02 to 0.79 ± 0.04. The predictive power of the optimal models was validated by compounds with known potencies as CYP3A7/CYP3A4 inhibitors or substrates. In addition, we identified structural features significant for CYP3A7/CYP3A4 selective or common inhibitors and substrates. In summary, the top performing models can be further applied as a tool to rapidly evaluate the safety and efficacy of new drugs separately for fetuses/neonates and adults. The significant structural features could guide the design of new therapeutic drugs as well as aid in the optimization of existing medicine for fetuses/neonates.

Progress in the Consideration of Possible Sex Differences in Drug Interaction Studies

Background:

Anecdotal evidence suggests that there may be sex differences in Drug-drug Interactions (DDI) involving specific drugs. Regulators have provided general guidance for the inclusion of females in clinical studies. Some clinical studies have reported sex differences in the Pharmacokinetics (PK) of CYP3A4 substrates, suggesting that DDI involving CYP3A4 substrates could potentially show sex differences.

Objective:

The aim of this review was to investigate whether recent prospective DDI studies have included both sexes and whether there was evidence for the presence or absence of sex differences with the DDIs.

Methods:

The relevant details from 156 drug interaction studies within 124 papers were extracted and evaluated.

Results:

Only eight studies (five papers) compared the outcome of the DDI between males and females. The majority of the studies had only male volunteers. Five studies had females only while 60 had males only, with 7.7% of the studies having an equal proportion of both sexes. Surprisingly, four studies did not specify the sex of the subjects.

:

Based on the limited number of studies comparing males and females, no specific trends or conclusions were evident. Sex differences in the interaction were reported between ketoconazole and midazolam as well as clarithromycin and midazolam. However, no sex difference was observed with the interaction between clarithromycin and triazolam or erythromycin and triazolam. No sex-related PK differences were observed with the interaction between ketoconazole and domperidone, although sex-related differences in QT prolongation were observed.

Conclusion:

This review has shown that only limited progress had been made with the inclusion of both sexes in DDI studies.

Almotriptan: a review of 20 years' clinical experience

Introduction: Almotriptan (ALT), a serotonin 5-HT_1B/1D agonist has been used in the acute treatment of migraine with or without aura for 20 years, accumulating data on more than 15,000 patients in studies and from an estimated >150 million treated migraine attacks in daily clinical practice. The last major review of ALT was written almost 10 years ago. The current narrative review provides an overview of the experience gained with almotriptan over that time, and highlights data published in the last decade. Areas covered: Randomized clinical trials, observational studies, postmarketing studies and meta-analyses involving ALT for the treatment of acute migraine identified through a systematic literature search. Expert opinion: Triptans are a mainstay of anti-migraine treatment. Findings with ALT over the last 10 years have reinforced the positive efficacy and tolerability results that were reported during the first 10 years following its introduction. In particular, more recent clinical results have confirmed its efficacy in women with menstrual migraine, the usefulness of early intervention, long-term benefit in adults, and also its efficacy and safety in adolescents. Overall, ALT can be considered an optimal choice for managing acute migraine resistant to first-line drugs.

Clinical Profile and Practice Experience of Almotriptan

Patients expect their acute migraine treatment to have a rapid onset of action, achieve complete pain relief that is sustained for 24 h, and to have a good tolerability profile. Almotriptan has a favourable pharmacokinetic profile that translates clinically to a rapid onset of action and consistent absorption regardless of age, sex, food intake and status of the acute migraine attack. In addition, almotriptan is not associated with any clinically relevant drug-drug interactions. Pain-free status at 2 h postdose is achieved by approximately 39% of patients receiving almotriptan in clinical trials. Recurrence of headaches within 24 h is low with almotriptan (< 22%). Almotriptan has a sustained pain-free rate of 25-27%, which in a meta-analysis of triptans was superior to sumatriptan 100 mg. Almotriptan therapy is associated with a low incidence of adverse events, including those affecting the central nervous system and chest.

Medication overuse and chronic migraine: a critical review according to clinical pharmacology

INTRODUCTION

Chronic migraine is often complicated by medication-overuse headache (MOH), a headache due to excessive intake of acute medications. Chronic migraine and MOH are serious and disabling disorders. Since chronic migraine derives from the progression of originally episodic migraine, the fundamental therapeutic strategy is prevention. This narrative review describes how to try to prevent the development of MOH and how to manage it once it has appeared.

AREAS COVERED

A PubMed database search (from 1988 to January 2015) and a review of published studies on chronic migraine and MOH were conducted.

EXPERT OPINION

In spite of progress in migraine treatment, the prevalence of chronic headaches and MOH has not changed in the course of time. Today, a large number of migraine patients have turned to numerous expert physicians and experienced all sorts of prophylactic treatments without decisive benefits. Their condition seems to have crystallized even more as chronic and intractable. This means that to prevent chronification and MOH, we need more effective drugs and better strategies to use them. In particular, we must detect disease biomarkers and predictive factors for drug response that allow for personalized treatment when migraine is still episodic and make analgesic overuse pointless.

Drug interactions with triptans : which are clinically significant?

The triptans are a group of compounds with high efficacy for the acute treatment of migraine and cluster headache. They have a relatively wide therapeutic index, and although a number of minor pharmacokinetic interactions have been observed, few are likely to be clinically significant. Given the differences in principal elimination pathways, potentially interacting drugs on a pharmacokinetic basis are not common across all compounds. Of more concern than pharmacokinetic interactions are pharmacodynamic interactions. Of most concern, additive vasoconstrictor effects are likely to occur with other vasoconstrictors, especially the ergots used for migraine. Serotonin syndrome has been observed due to coadministration of triptans with selective serotonin reuptake inhibitors (SSRIs), but the absolute rate of such a clinical response to coadministration is probably low. Most patients can take triptans with other medications without dose alteration, although vigilance is required for pharmacodynamic interactions.

Comparative study of the affinity and metabolism of type I and type II binding quinoline carboxamide analogues by cytochrome P450 3A4

Compounds that coordinate to the heme-iron of cytochrome P450 (CYP) enzymes are assumed to increase metabolic stability. However, recently we observed that the type II binding quinoline carboxamide (QCA) compounds were metabolically less stable. To test if the higher intrinsic clearance of type II binding compounds relative to type I binding compounds is general for other metabolic transformations, we synthesized a library of QCA compounds that could undergo N-dealkylation, O-dealkylation, benzylic hydroxylation, and aromatic hydroxylation. The results demonstrated that type II binding QCA analogues were metabolically less stable (2- to 12-fold) at subsaturating concentration compared to type I binding counterparts for all the transformations. When the rates of different metabolic transformations between type I and type II binding compounds were compared, they were found to be in the order of N-demethylation > benzylic hydroxylation> O-demethylation > aromatic hydroxylation. Finally, for the QCA analogues with aza-heteroaromatic rings, we did not detect metabolism in aza-aromatic rings (pyridine, pyrazine, pyrimidine), indicating that electronegativity of the nitrogen can change regioselectivity in CYP metabolism.

Almotriptan: a review of 10 years' clinical experience

Almotriptan, a serotonin 5-HT 1B/1D agonist, was developed for the acute treatment of migraine with or without aura and has been available for 10 years. This article evaluates the wealth of experience that has been obtained with almotriptan, including large randomized clinical trials (RCTs) and post-marketing studies that more closely reflect everyday clinical practice. Initial RCTs required patients to take almotriptan when migraine pain was of moderate or severe intensity, and found that 12.5 mg provided optimal outcomes for both pain relief and tolerability. Almotriptan effectively improved 2-h pain-relief, reduced migraine-associated symptoms and demonstrated low recurrence rates. These findings were also shown in patient subgroups, such as adolescents and menstrual migraineurs. A secondary finding in these trials was that patients who took almotriptan early, when the pain was still mild, achieved better outcomes. This prompted the initiation of studies designed to assess the effect of almotriptan in early intervention. Open-label trials reported improvements in pain-free end points (2 h, 24 h), and subsequent RCTs confirmed these findings. Pharmacovigilance data from more than 100 million tablets dispensed worldwide have confirmed that almotriptan is associated with a low occurrence of adverse effects, which, in clinical trials, has been shown to be similar to that observed with placebo. The clinical evidence obtained and comparisons made over a decade of use have demonstrated that almotriptan is one of the more effective and fast-acting triptans available, with a placebo-like tolerability profile. This suggests that almotriptan is an excellent choice for patients requiring specific acute migraine treatment.

Inhibition of Cytochrome P450 3A4 by a Pyrimidineimidazole: Evidence for Complex Heme Interactions

PH-302 inhibits the inducible form of nitric oxide synthase (iNOS) by coordinating with the heme of the monomeric form and preventing formation of the active dimer. Inherent with the mechanism of pharmacology for this compound was the inhibition of cytochrome P450 3A4 (P450 3A4), observed from early ADME screening. Further investigation showed that PH-302 inhibited P450 3A4 competitively with a Ki of approximately 2.0 microM against both midazolam and testosterone hydroxylation in human liver microsomes. As expected, spectral binding analysis demonstrated that inhibition was a result of type II coordination to the P450 heme with the imidazole moiety of PH-302, although only 72% of the maximal absorbance difference was achievable with PH-302 compared to that of the smaller ligand imidazole. Time-dependent inhibition of P450 3A4 by PH-302 was also observed because of metabolite-inhibitory (MI) complex formation via metabolism of the methylenedioxyphenyl group. The profile for time-dependent inhibition in recombinant P450 3A4 was biphasic, and was kinetically characterized by a kinact of 0.08 min-1 and a Ki of 1.2 microM for the first phase (0-1.5 min) and a kinact of 0.06 min-1 and a Ki of 23.8 microM for the second phase (1.5-10 min). Spectral characterization of the PH-302 MI complex demonstrated that formation began to plateau within 3 min, consistent with the kinetic profile of inactivation by PH-302. Meanwhile, spectral evidence for the imidazole-derived type II difference spectrum of PH-302 was captured simultaneously with the formation of the MI complex. The presence of simultaneously operable type II coordination and rapidly saturable MI complex formation with heme by PH-302 indicates the presence of complex heme interactions with this unique molecule. Information from these mechanistic studies adds to our understanding of the nature of P450 3A4 inhibition by PH-302 and provides a potentially useful tool compound for future studies investigating binding interactions in this important drug-metabolizing enzyme.

Determination of the enzyme(s) involved in the metabolism of amiodarone in liver and intestine of rat: the contribution of cytochrome P450 3A isoforms

In humans, cytochrome P450 3A (CYP3A4) is a major enzyme involved in the metabolism of amiodarone (AM) to its major metabolite, desethylamiodarone (DEA). In rat, a commonly used animal model, metabolism of AM has not been well studied. To determine whether DEA is formed by CYP3A isoenzymes in the rat, microsomal protein was harvested from liver and intestine of male Sprague-Dawley rats. The metabolism of AM in each tissue was assessed utilizing chemical and immunological inhibitors. Ketoconazole, a presumed inhibitor of CYP3A1/2, significantly inhibited formation of DEA by hepatic and intestinal microsomes. However, based on the DEA formation kinetics in both microsomal preparations, it appeared that more than one cytochrome P450 enzyme was involved in the process. Coincubation of AM with microsomes and anti-CYP3A2 confirmed the role of CYP3A2 in the metabolism of AM in liver. DEA was also formed by rat recombinant CYP1A1 and CYP3A1, and was inhibited by ketoconazole; hence the participation of these enzymes in the intestinal DEA formation is likely. However, anti-CYP2B1/2 or -CYP1A2 antibodies had no effect on DEA formation. In rats given oral or intravenous AM, oral ketoconazole caused significant increases in area under the concentration versus time curve (AUC) of oral and i.v. treated rats and greater than 50% decreases in the total body clearance and Vdss of i.v. treated rats. Although low to undetectable concentrations of DEA were a limitation for determination of AUC of DEA in vivo, it was confirmed that ketoconazole could cause a significant increase in AM concentrations in rat.

Focus on trial endpoints of clinical relevance and the use of almotriptan for the acute treatment of migraine

Almotriptan is a 5-HT(1B/1D) receptor agonist, or triptan, indicated for the acute treatment of migraine. It has been shown to be effective and well tolerated for the treatment of acute migraine in approximately 5000 patients enrolled in short-term placebo- and active-controlled trials and long-term open-label trials. A recent meta-analysis reported that almotriptan has the highest sustained pain-free (SPF) rate and lowest adverse-event (AE) rate of all oral triptans. Sustained pain free is a composite endpoint of pain freedom at 2 h, no recurrence of moderate-to-severe headache and no use of rescue medication from 2 to 24 h after dosing. Patient surveys have indicated that migraine sufferers consider complete pain relief, no recurrence, rapid onset and no side-effects to be the most important attributes of their acute treatment. Composite endpoints such as SPF and SPF with no AEs (SNAE) contain the attributes that migraine sufferers express as being the most important elements of an acute migraine therapy, and their use in future clinical trials should aid in the selection of agents that can offer patients the highest likelihood of consistent treatment success.