Frovatriptan: a review of drug-drug interactions

The impact of genetic factors on the response to migraine therapy

Migraine is a multidimensional disease affecting a large portion of the human population presenting with a variety of symptoms. In the era of personalized medicine, successful migraine treatment presents a challenge, as several studies have shown the impact of a patient's genetic profile on therapy response. However, with the emergence of contemporary treatment options, there is promise for improved outcomes. A literature search was conducted in PubMed and Scopus, in order to obtain studies investigating the impact of genetic factors on migraine therapy outcome. Overall, 23 studies were included in the current review, exhibiting diversity in the treatments used and the genetic variants investigated. Divergent genes were assessed for each category of migraine treatment. Several genetic factors were identified to contribute to the heterogeneous response to treatment. SNPs related to pharmacodynamic receptors, pharmacogenetics and migraine susceptibility loci were the most investigated variants, revealing some interesting significant results. To date, various associations have been recorded correlating the impact of genetic factors on migraine treatment responses. More extensive research needs to take place with the aim of shedding light on the labyrinthine effects of genetic variations on migraine treatment, and, consequently, these findings can promptly affect migraine treatment and improve migraine patients' life quality in the vision of precise medicine.

Drug Safety in Episodic Migraine Management in Adults. Part 2: Preventive Treatments

PURPOSE OF REVIEW

The aim of this review is to aid in decision-making when choosing safe and effective options for preventive migraine medications.

RECENT FINDINGS

In Part 2, we have compiled clinically relevant safety considerations for commonly used migraine prophylactic treatments. Preventive treatment of episodic migraine includes nonspecific and migraine-specific drugs. While medications from several pharmacological classes-such as anticonvulsants, beta-blockers, and antidepressants-have an established efficacy in migraine prevention, they are associated with a number of side effects. The safety of migraine-specific treatments such as anti-CGRP monoclonal antibodies and gepants are also discussed. This review highlights safety concerns of commonly used migraine prophylactic agents and offers suggestions on how to mitigate those risks.

Effects of CYP3A4 and P-glycoprotein inhibition or induction on the pharmacokinetics of ubrogepant in healthy adults: Two phase 1, open-label, fixed-sequence, single-center, crossover trials

Background:

Ubrogepant is metabolized by cytochrome P450 3A4 (CYP3A4) and is a P-glycoprotein (P-gp) substrate.

Objective:

To assess effects of multiple-dose moderate-strong CYP3A4 and strong P-gp inhibitors and inducers on ubrogepant pharmacokinetic (PK) parameters.

Methods:

Two phase 1, open-label, fixed-sequence, single-center, crossover trials enrolled healthy adults to receive ubrogepant 20 mg with/without verapamil 240 mg (a moderate CYP3A4 inhibitor) or ketoconazole 400 mg (a strong CYP3A4 and P-gp transporter inhibitor) (Study A), or ubrogepant 100 mg with/without rifampin 600 mg (a strong CYP3A4 inducer and P-gp inducer) (Study B). Outcomes included ubrogepant PK parameters (area under plasma concentration-time curve, time 0 through infinity [AUC0-∞], peak plasma concentration [Cmax]), and safety (treatment-emergent adverse events [TEAEs]). PK parameters were compared between ubrogepant with/without coadministered medications using linear mixed-effects models. Cmax and AUC0-∞ least-squares geometric mean ratios (GMR) of ubrogepant with/without coadministration were constructed.

Results:

Twelve participants enrolled in Study A and 30 in Study B. AUC0-∞ and Cmax GMR (90% CI) were 3.53 (3.32–3.75) and 2.80 (2.48–3.15), respectively, for ubrogepant with verapamil; 9.65 (7.27–12.81) and 5.32 (4.19–6.76) with ketoconazole; and 0.22 (0.20–0.24) and 0.31 (0.27–0.36) with rifampin. TEAEs were predominantly mild; no treatment-related serious TEAEs or TEAE-related discontinuations occurred.

Conclusion:

The PK of ubrogepant were significantly affected by the concomitant use of CYP3A4 moderate-strong inhibitors and strong inducers.

Tobacco smoking and its drug interactions with comedications involving CYP and UGT enzymes and nicotine

Tobacco smoking is a global public health threat causing several illnesses including cardiovascular disease (Myocardial infarction), cerebrovascular disease (Stroke), peripheral vascular disease (Claudication), chronic obstructive pulmonary disease, asthma, reduced female infertility, sexual dysfunction in men, different types of cancer and many other diseases. It has been estimated in 2015 that approximately 1.3 billion people smoke, around the globe. Use of medications among smokers is more common, nowadays. This review is aimed to identify the medications affected by smoking, involving Cytochrome P450 (CYP) and uridine diphosphate-glucuronosyltransferases (UGTs) enzymes and Nicotine. Polycyclic aromatic hydrocarbons (PAHs) of tobacco smoke have been associated with the induction of CYP enzymes such as CYP1A1, CYP1A2 and possibly CYP2E1 and UGT enzymes. The drugs metabolized by CYP1A1, CYP1A2, CYP2E1 and UGT enzymes might be affected by tobacco smoking and the smokers taking medications metabolized by those enzymes, may need higher doses due to decreased plasma concentrations through enhanced induction by PAHs of tobacco smoke. The prescribers and the pharmacists are required to be aware of medications affected by tobacco smoking to prevent the toxicity-associated complications during smoking cessation.

Efficacy and pharmacokinetic activity of frovatriptan compared to rizatriptan in patients with moderate-to-severe migraine

BACKGROUND

Migraine is a painful neurological disorder that affects over 10% of the general population. Frovatriptan and rizatriptan are antimigraine agents belonging to the triptan class. Although previous studies have independently compared the efficacy of these agents, contemporaneous data examining both pharmacokinetic (PK) properties and efficacy in parallel have not previously been available.

MATERIALS AND METHODS

In this single-center double-blind study, 18 subjects (ten female) were treated for a single migraine attack with frovatriptan 2.5 mg or rizatriptan 10 mg. Plasma concentrations were measured predose and at 2, 4, 6, 12, 24, 48, and 72 hours after drug administration. The primary end point of this study was to evaluate the association between PK parameters and efficacy measures and recurrence rate. Secondary end points were pain-free and pain-relief episodes at 2 and 4 hours, recurrent episodes within 48 hours, and cumulative hazard of recurrence within 72 hours.

RESULTS

At baseline, approximately 17% of patients had mild migraine, while 83% had moderate-severe migraine. Although the time to maximum concentration was similar for both drugs (2.7 versus 2.3 hours), the terminal half-life for frovatriptan was longer than rizatriptan (29.3 versus 3.2 hours, P<0.0001). The proportion of patients who were pain-free at 4 hours without rescue medication was higher in the frovatriptan-treated group, (38.9 versus 5.6%, P=0.045). The cumulative hazard of recurrence over 72 h was reduced by frovatriptan compared to rizatriptan-treated patients (log-rank test, P=0.04). Pain-free and pain-relief episodes for the study period were positively correlated with the concentration:maximum concentration (Cmax) ratio for frovatriptan (r=0.52, P=0.028), but not rizatriptan. Recurrence rate was negatively correlated with the concentration:Cmax ratio for both frovatriptan (r=-0.96, P=0.0024) and rizatriptan (r=-0.98, P=0.0004). Fewer adverse events were observed for frovatriptan compared to rizatriptan (one versus eight, P=0.021).

CONCLUSION

This pilot study indicates that a similar extent of initial pain relief is afforded by both triptans in migraine treatment. The longer duration of action of frovatriptan parallels and correlates with its PK profile.

A review of frovatriptan for the treatment of menstrual migraine

The objective of this review is to provide an overview of menstrual migraine (MM) and of frovatriptan and to assess clinical trial data regarding the efficacy and safety of frovatriptan for the acute and short-term prophylaxis of MM. Randomized controlled trials comparing frovatriptan with placebo or a triptan comparator for the acute or prophylactic treatment of MM were selected for review. MM affects up to 60% of women with migraine. Compared with attacks at other times of the cycle, menstrual attacks are longer, more severe, less responsive to treatment, more likely to relapse, and more disabling than attacks at other times of the cycle. No drugs are licensed for acute treatment of MM; triptans are recommended for treatment of moderate to severe attacks for menstrual and nonmenstrual attacks. Perimenstrual prophylaxis is indicated for patients with predictable MM that does not respond to symptomatic treatment alone. Treatment is unlicensed, but options include triptans, nonsteroidal anti-inflammatory drugs, and hormone manipulation. Frovatriptan is distinctive from other triptans due to its long elimination half-life of 26 hours, which confers a longer duration of action. Post hoc analyses from randomized trials of MM show similar pain relief and pain-free rates for frovatriptan compared with other triptans (2 hours pain-free: relative risk [RR] 1.27, 95% confidence interval [CI] 0.91–1.76) but significantly lower relapse rates (24 hours sustained pain-free: RR 0.34, 95% CI 0.18–0.62). Data from randomized controlled trials show a significant reduction in risk of MM in women using frovatriptan 2.5 mg once daily (RR 1.56, 95% CI 1.31–1.86) or twice daily (RR 1.98, 95% CI 1.68–2.34) for perimenstrual prophylaxis compared with placebo. The twice daily dosing was more effective than once daily (RR 1.27, 95% CI 1.11–1.46). These findings support the use of frovatriptan as a first-line acute treatment for MM and for perimenstrual prophylaxis.

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.

Frovatriptan: a review of its use in the acute treatment of migraine

Frovatriptan (Migard®; Frova®) is an orally administered triptan approved for the acute treatment of adults with migraine, with or without aura. This article reviews the pharmacology of frovatriptan, focusing on its efficacy and tolerability. The precise mechanism of action of frovatriptan is unknown, but is thought to stem from agonism at serotonin 5-HT(1B) and 5-HT(1D) receptors, resulting in inhibition of intracranial and extracerebral artery vasodilation, along with possible anti-inflammatory and pain inhibiting effects. Frovatriptan appears to be functionally selective for 5-HT receptors in human basilar arteries over coronary arteries, which could translate into a low cardiovascular risk. In contrast to other triptans, frovatriptan has a long terminal elimination half-life in blood of ≈26 hours, which can be expected to be associated with a sustained treatment effect. Oral frovatriptan 2.5 mg was efficacious in patients with moderate to severe migraine attacks; in randomized, double-blind trials the proportion of patients with headache response at 2 hours (primary endpoint) was consistently significantly higher in frovatriptan than placebo groups. Frovatriptan was generally well tolerated in short-term clinical trials and when used over the longer term. The most frequent treatment-emergent adverse events occurring at a frequency ≥1% higher in frovatriptan than placebo recipients were dizziness, fatigue, headache, paraesthesia, flushing, skeletal pain, hot or cold sensation, dry mouth, chest pain and dyspepsia. In a study in patients with coronary artery disease, or who were at high risk of coronary artery disease, there was no increase over placebo in the occurrence of clinically significant ECG changes or in cardiac rhythm disturbances. In a further trial, frovatriptan administered early in a migraine attack was more efficacious than placebo followed by later administration of frovatriptan as pain progressed. Three crossover trials compared early administration of frovatriptan 2.5 mg with almotriptan 12.5 mg, rizatriptan 10 mg and zolmitriptan 2.5 mg in patients with migraine. There were no significant between-group differences in patient drug preference scores (primary endpoint) or in other endpoints, except for headache recurrence, which favoured frovatriptan in two of the trials. The trials did not test noninferiority of frovatriptan to the comparator. In a placebo-controlled trial that included a sumatriptan active treatment arm, sumatriptan 100 mg was significantly more efficacious than frovatriptan 2.5 mg for this primary endpoint. Frovatriptan was generally better tolerated than all four triptan comparators. In summary, frovatriptan was an efficacious acute treatment for moderate to severe migraine attacks and had a favourable tolerability profile, although in a single trial, it was not as efficacious as sumatriptan. Administration of frovatriptan early in an attack while the attack was at a mild level of intensity was more efficacious than late administration. Furthermore, in clinical trials adopting this early administration strategy, frovatriptan was not significantly less efficacious than almotriptan, rizatriptan and zolmitriptan, appeared to have a more sustained treatment effect, and was better tolerated than the comparators. Frovatriptan provides an alternative treatment for migraine, especially in patients who have had adverse events or frequent headache recurrences with triptans or other antimigraine drugs, and who are amenable to adopting an early administration strategy.

Pharmacokinetic evaluation of frovatriptan

INTRODUCTION

Migraine is the most common painful neurological disorder, affecting 13% of the general population. Triptans represent a powerful pharmacological tool in acute migraine treatment, however, a significant portion of treated patients cannot have access to this class due to possible adverse affects. Today, a total of seven triptan molecules are available, representing a commonly prescribed migraine treatment. Although there is a need of extensive use of triptans, only 25% of migraine patients are using triptans.

AREAS COVERED

This review includes triptans and evidence for the use of frovatriptan. A systematic approach is used to discuss the pharmacodynamic and pharmacokinetic aspects of frovatriptan, considering the emerging data on the clinical efficacy of frovatriptan in the treatment of migraine and cluster headaches. The data were obtained by searching the following key words in MEDLINE: pharmacokinetic, pharmacodynamic, triptans, frovatriptan, migraine, menstrual migraine, relatively to the period 1988 - 2011.

EXPERT OPINION

Frovatriptan has been developed in order to improve safety and efficacy of triptans. It shows a favorable tolerability and efficacy profile, limited to 24/48-h headache recurrence, when compared with other triptans. Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from other available triptans. In fact, among triptans, frovatriptan showed the highest potency at the 5-HT1B receptor (8.2) and the longer half-life (26 h). These parameters determine the clinical properties of frovatriptan; in particular the lowest rate of headache recurrence in comparison with other triptans.

Frovatriptan versus other triptans in the acute treatment of migraine: pooled analysis of three double-blind, randomized, cross-over, multicenter, Italian studies

The objective of the study is to systematically review the efficacy and safety of frovatriptan (F) versus rizatriptan (R), zolmitriptan (Z) and almotriptan (A), through a pooled analysis of three individual studies. 414 subjects with a history of migraine with or without aura (IHS criteria) were randomized to F 2.5 mg or R 10 mg (study 1), F 2.5 mg or Z 2.5 mg (study 2), and F 2.5 mg or A 12.5 mg (study 3). The studies had an identical multicenter, randomized, double blind, cross-over design, with each of the two treatment periods lasting not more than 3 months. The number of pain free (PF) and pain relief (PR) episodes at 2 h, and the number of sustained pain free (SPF) and recurrent episodes within the 48 h were the efficacy endpoints. 346 patients were included in the intention-to-treat analysis. Rate of PF episodes at 2 h was 30% with F and 34% with comparators (p = NS). PR episodes at 2 h were 55% for F and 59% for comparators (p = NS). SPF episodes at 48 h were also similar between the two groups (22% F vs. 21% comparators). Rate of recurrence was significantly (p < 0.001) lower under F (27 vs. 40% comparators). Drug-related adverse events were significantly (p < 0.05) less under F, particularly cardiovascular symptoms. Our systematic analysis of individual studies suggests that F has a similar immediate efficacy, but a more sustained effect and a better tolerability than R, Z and A.

A double-blind, randomized, multicenter, Italian study of frovatriptan versus almotriptan for the acute treatment of migraine

The objective of this study was to evaluate patients’ satisfaction with acute treatment of migraine with frovatriptan or almotriptan by preference questionnaire. One hundred and thirty three subjects with a history of migraine with or without aura (IHS 2004 criteria), with at least one migraine attack in the preceding 6 months, were enrolled and randomized to frovatriptan 2.5 mg or almotriptan 12.5 mg, treating 1–3 attacks. The study had a multicenter, randomized, double blind, cross-over design, with treatment periods lasting <3 months. At study end patients assigned preference to one of the treatments using a questionnaire with a score from 0 to 5 (primary endpoint). Secondary endpoints were pain free and pain relief episodes at 2 and 4 h, and recurrent and sustained pain free episodes within 48 h. Of the 133 patients (86%, intention-to-treat population) 114 of them expressed a preference for a triptan. The average preference score was not significantly different between frovatriptan (3.1 ± 1.3) and almotriptan (3.4 ± 1.3). The rates of pain free (30% frovatriptan vs. 32% almotriptan) and pain relief (54% vs. 56%) episodes at 2 h did not significantly differ between treatments. This was the case also at 4 h (pain free: 56% vs. 59%; pain relief: 75% vs. 72%). Recurrent episodes were significantly (P < 0.05) less frequent under frovatriptan (30% vs. 44%), also for the attacks treated within 30 min. No significant differences were observed in sustained pain free episodes (21% vs. 18%). The tolerability profile was similar between the two drugs. In conclusion, our study suggests that frovatriptan has a similar efficacy of almotriptan in the short-term, while some advantages are observed during long-term treatment.

A double-blind, randomized, multicenter, Italian study of frovatriptan versus rizatriptan for the acute treatment of migraine

The objective of this study was to assess patient satisfaction with acute treatment of migraine with frovatriptan or rizatriptan by preference questionnaire. 148 subjects with a history of migraine with or without aura (IHS 2004 criteria), with at least one migraine attack per month in the preceding 6 months, were enrolled and randomized to frovatriptan 2.5 mg or rizatriptan 10 mg treating 1-3 attacks. The study had a multicenter, randomized, double-blind, cross-over design, with treatment periods lasting <3 months. At the end of the study, patients assigned preference to one of the treatments using a questionnaire with a score from 0 to 5 (primary endpoint). Secondary endpoints were pain-free and pain relief episodes at 2 h, and recurrent and sustained pain-free episodes within 48 h. 104 of the 125 patients (83%, intention-to-treat population) expressed a preference for a triptan. The average preference score was not significantly different between frovatriptan (2.9±1.3) and rizatriptan (3.2±1.1). The rates of pain-free (33% frovatriptan vs. 39% rizatriptan) and pain relief (55 vs. 62%) episodes at 2 h were not significantly different between the two treatments. The rate of recurrent episodes was significantly (p<0.001) lower under frovatriptan (21 vs. 43% rizatriptan). No significant differences were observed in sustained pain-free episodes (26% frovatriptan vs. 22% rizatriptan). The number of patients with adverse events was not significantly different between rizatriptan (34) and frovatriptan (25, p=NS). The results suggest that frovatriptan has a similar efficacy to rizatriptan, but a more prolonged duration of action.

Disposition and metabolism of almotriptan in rats, dogs and monkeys

Almotriptan is a new highly potent selective 5-HT1B/1D receptor agonist developed for the treatment of migraine, and the disposition of almotriptan in different animal species is now addressed in the current study. Almotriptan was well absorbed in rats (69.1%) and dogs (100%) following oral treatment. The absolute bioavailability was variable reflecting different degrees of absorption and first-pass metabolism (18.7-79.6%). The elimination half-life was short and ranged between 0.7 and 3 h. The main route of elimination of almotriptan was urine with 75.6% and 80.4% of the dose recovered over a 168-h period in rats and dogs, respectively. The gamma-aminobutyric acid metabolite formed by oxidation of the pyrrolidine ring was the main metabolite found in urine, faeces, bile, and plasma of rats and in monkey urine. By contrast, the unchanged drug, the indole acetic acid metabolite formed by oxidative deamination of the dimethylaminoethyl group, and the N-oxide metabolite were the main metabolites in dog.

Inhibition and induction of human cytochrome P450 enzymes: current status

Variability of drug metabolism, especially that of the most important phase I enzymes or cytochrome P450 (CYP) enzymes, is an important complicating factor in many areas of pharmacology and toxicology, in drug development, preclinical toxicity studies, clinical trials, drug therapy, environmental exposures and risk assessment. These frequently enormous consequences in mind, predictive and pre-emptying measures have been a top priority in both pharmacology and toxicology. This means the development of predictive in vitro approaches. The sound prediction is always based on the firm background of basic research on the phenomena of inhibition and induction and their underlying mechanisms; consequently the description of these aspects is the purpose of this review. We cover both inhibition and induction of CYP enzymes, always keeping in mind the basic mechanisms on which to build predictive and preventive in vitro approaches. Just because validation is an essential part of any in vitro-in vivo extrapolation scenario, we cover also necessary in vivo research and findings in order to provide a proper view to justify in vitro approaches and observations.

Indolealkylamines: biotransformations and potential drug-drug interactions

Indolealkylamine (IAA) drugs are 5-hydroxytryptamine (5-HT or serotonin) analogs that mainly act on the serotonin system. Some IAAs are clinically utilized for antimigraine therapy, whereas other substances are notable as drugs of abuse. In the clinical evaluation of antimigraine triptan drugs, studies on their biotransformations and pharmacokinetics would facilitate the understanding and prevention of unwanted drug-drug interactions (DDIs). A stable, principal metabolite of an IAA drug of abuse could serve as a useful biomarker in assessing intoxication of the IAA substance. Studies on the metabolism of IAA drugs of abuse including lysergic acid amides, tryptamine derivatives and beta-carbolines are therefore emerging. An important role for polymorphic cytochrome P450 2D6 (CYP2D6) in the metabolism of IAA drugs of abuse has been revealed by recent studies, suggesting that variations in IAA metabolism, pharmaco- or toxicokinetics and dynamics can arise from distinct CYP2D6 status, and CYP2D6 polymorphism may represent an additional risk factor in the use of these IAA drugs. Furthermore, DDIs with IAA agents could occur additively at the pharmaco/toxicokinetic and dynamic levels, leading to severe or even fatal serotonin toxicity. In this review, the metabolism and potential DDIs of these therapeutic and abused IAA drugs are described.

Review of frovatriptan in the treatment of migraine

Triptans are recommended for the acute treatment of moderate to severe migraine or failure to respond to other acute migraine treatments. Seven triptans are available providing a wide range of choices. These triptans are more similar than dissimilar but patients do note differences in effectiveness and in tolerance. Also migraine situations may differ from attack to attack, providing the opportunity to exploit the uniqueness of a particular triptan. Frovatriptan has a uniquely long-half life, five times that of other triptans. This provides the opportunity to use frovatriptan in mini-prophylaxis such as in menstrual-related migraine and other situations, as well as use in long-lasting or recurrent migraine.

Amine oxidases and monooxygenases in the in vivo metabolism of xenobiotic amines in humans: has the involvement of amine oxidases been neglected?

In this review, the major enzyme systems involved in vivo in the oxidative metabolism of xenobiotic amines in humans are discussed, i.e. the monooxygenases [cytochrome P450 system (CYPs) and flavin-containing monooxygenases (FMOs)] and the amine oxidases (AOs). Concerning the metabolism of xenobiotic amines (drugs in particular) by monoamine oxidases (MAOs), this aspect has been largely neglected in the past. An exception is the extensive investigation carried out on the inhibition of the metabolism of tyramine, when tyramine-containing food is ingested by subjects taking inhibitors of MAO A or of both MAO A and B. Moreover, investigations in humans on the metabolism of drug amines on the market by AOs, such as semicarbazide-sensitive amine oxidases (SSAOs) and polyamine oxidases (PAOs), are practically nonexistent, with the exception of amlodipine. In contrast to MAOs, monooxygenases (CYP isoenzymes more than FMOs) have been extensively investigated concerning their involvement in the metabolism of xenobiotics. It is possible that the contribution of AOs to the overall metabolism of xenobiotic amines in humans is underestimated or erroneously estimated, as most investigations of drug metabolism are performed using in vitro test systems optimized for CYP activity, such as liver microsomes, and most investigations of drug metabolism in vivo in humans carry out only the identification of the final, stable metabolites. However, for some drugs on the market, the involvement of MAOs in their in vivo metabolism in humans has been demonstrated recently, among these drugs citalopram, sertraline and the triptans are examples that can be mentioned.

Efficacy and tolerability of frovatriptan in acute migraine treatment: systematic review of randomized controlled trials

OBJECTIVE

To evaluate the efficacy and tolerability of frovatriptan in acute migraine treatment.

METHODS

Systematic review and meta-analysis of randomized controlled trials. Clinical trials of frovatriptan were systematically identified through electronic searches and historical searches up until February 2005. Studies were included if they were (i) double-blind, randomized, placebo controlled trials that evaluated frovatriptan 2.5 mg in acute migraine treatment and (ii) reporting the efficacy data in terms of pain-free, headache response, headache recurrence, or relief of migraine-associated symptoms. Two authors extracted data independently. Disagreements were resolved through discussion. The efficacy was estimated using risk ratio (RR), risk difference, and number needed to treat together with 95% confidence intervals.

RESULTS

Five trials involving a total of 2,866 patients were included. Frovatriptan 2.5 mg was more effective than placebo in rendering patient pain-free (RR 3.70, 95% CI 2.59-5.29, P < 0.0001 at 2 h and 2.67, 95% CI 2.21-3.22, P < 0.0001 at 4 h post-dose). It was also superior to placebo in reducing headache severity. The pooled RR was 1.66 (95% CI 1.48-1.88, P < 0.0001) and 1.83 (95% CI 1.66-2.00, P < 0.0001), respectively, at 2 and 4 h after treatment. In those whose headache was relieved at 4 h, the risk of headache recurrence within 24 h was reduced by 26% with frovatriptan (RR 0.74, 95% CI 0.59-0.93, P = 0.009). Frovatriptan was also superior to placebo in improving symptoms associated with migraine. At 2 h after dosing, frovatriptan reduced the risk of nausea by 14% (95% CI 6-20%, P = 0.0005), photophobia 17% (95% CI 12-22%, P < 0.0001), and phonophobia 14% (95% CI 17-20%, P < 0.0001). The corresponding numbers at 4 h after dosing were 37% (95% CI 30-43%, P < 0.0001), 34% (95% CI 29-39%, P < 0.0001) and 30% (95% CI 23-36%, P < 0.0001), respectively. Frovatriptan caused more adverse events than did placebo (RR 1.31, 95% CI 1.07-1.62, P = 0.01).

CONCLUSION

The available evidence suggests that frovatriptan is more effective but may cause more adverse events than placebo in the treatment of acute moderate to severe migraine. It is effective in providing pain relief and reducing the risk of recurrence. However, its effectiveness relative to other more established agents needs to be better defined by appropriate head to head trials.

Frovatriptan: clinical review and future directions

Triptan medications are selective serotonin receptor (5-HT1B/D) agonists approved for the treatment of acute migraine attacks. Among the currently available triptans, frovatriptan is unique with a long half-life (~26 h), metabolism by multiple pathways and a low side-effect profile. Clinical trial data demonstrates efficacy for frovatriptan across multiple doses, with the 2.5 mg dose selected for lower side effects. Frovatriptan is approved for use in the conventional treatment of an ongoing migraine attack, as are the other currently available triptan medications. The long half-life of frovatriptan has led to the initiation of studies of frovatriptan for the short-term prevention of menstrually related migraine attacks, during which patients are often difficult to treat. This newly investigated treatment approach for patients with predictable menstrually related migraine may, in the future, lead to treatment paradigms that benefit those patients with migraine attacks that are difficult to manage.

Assessment of CYP1A2 Activity in Clinical Practice: Why, How, and When?

The cytochrome P450 enzyme CYP1A2 mediates the rate-limiting step in the metabolism of many drugs including theophylline, clozapine, and tacrine as well as in the bioactivation of procarcinogens. CYP1A2 activity shows both pronounced intra- and interindividual variability, which is, among other factors, related to smoking causing enzyme induction, to drug intake and to dietary factors which may result in induction or inhibition. In contrast to these exogenous factors, genetic influences on enzyme activity seem to be less pronounced. Therefore, phenotyping of CYP1A2, i.e. the determination of the actual activity of the enzyme in vivo, represents a useful approach both for scientific and clinical applications. CYP1A2 is almost exclusively expressed in the liver. Since liver tissue cannot be obtained for direct phenotyping, a probe drug which is metabolized by CYP1A2 has to be given. Proposed probe drugs include caffeine, theophylline, and melatonin. Caffeine is most often used because of the predominating role of CYP1A2 in its overall metabolism and the excellent tolerability. Various urinary, plasma, saliva, and breath based CYP1A2 caffeine metrics have been applied. While caffeine clearance is considered as the gold standard, the salivary or plasma ratio of paraxanthine to caffeine in a sample taken approximately 6 hr after a defined dose of caffeine is a more convenient, less expensive but also fully validated CYP1A2 phenotyping metric. CYP1A2 phenotyping is applied frequently in epidemiologic and drug-drug interaction studies, but its clinical use and usefulness remains to be established.

Evaluating the safety and tolerability profile of acute treatments for migraine

Among the medications that have been used as acute treatments for migraine are nonspecific agents, including nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics (either single or combination), and narcotics, as well as migraine-specific medications, including ergot alkaloids and triptans (5-hydroxytryptamine 1B/1D agonists). All of these drugs have side effects that vary in type and severity. Side effects of nonspecific medications, including gastrointestinal (GI) and renal effects with NSAIDs and cognitive effects and the potential for abuse with narcotics and butalbital-containing medications, have been documented over time, as these medications have been used for various indications. Side effects of the migraine-specific medications include GI and vascular symptoms with the ergots; for the triptans, they include chest and neurologic symptoms. Although adverse events are reported fairly frequently in patients receiving triptans, they are usually mild, and few patients discontinue therapy because of them. The most serious adverse events are cardiovascular. Because of potential vasoconstrictor effects--mild and transient increases in blood pressure and mild and transient effects on coronary artery tone--triptans as a class are contraindicated in patients with established or clinically suspected cardiovascular disease, specifically ischemic heart disease and uncontrolled hypertension. Other adverse events, including the potential for drug-drug interactions, are less common. Therefore, consideration should be given to the tolerability and safety of medications before their use as abortive medications for the treatment of migraine headache.

Triptans and CNS side-effects: pharmacokinetic and metabolic mechanisms

Triptans are the treatment of choice for acute migraine. While seemingly a homogenous group of drugs, results from a meta-analysis reveal significant differences in efficacy and tolerability among oral triptans. The incidence of drug-related central nervous system (CNS) side-effects with some triptans is as high as 15% and may be associated with functional impairment and reduced productivity. The occurrence of adverse events associated with triptans in general, and CNS side-effects in particular, may lead to a delay in initiating or even avoidance of an otherwise effective treatment. Potential explanations for differences among triptans in the incidence of CNS side-effects may relate to pharmacological and pharmacokinetic differences, including receptor binding, lipophilicity, and the presence of active metabolites. Of the triptans reviewed, at clinically relevant doses, almotriptan 12.5 mg, naratriptan 2.5 mg and sumatriptan 50 mg had the lowest incidence of CNS side-effects, while eletriptan 40 and 80 mg, rizatriptan 10 mg and zolmitriptan 2.5 and 5 mg had the highest incidence. The most likely explanations for the differences in CNS side-effects among triptans are the presence of active metabolites and high lipophilicity of the parent compound and active metabolites. Eletriptan, rizatriptan and zolmitriptan have active metabolites, while lipophilicity is lowest for almotriptan and sumatriptan. If CNS side-effects are a clinically relevant concern in the individual patient, use of a triptan with a low incidence of CNS side-effects may offer the potential for earlier initiation of treatment and more effective outcomes.

Pharmacokinetics of frovatriptan in adolescent migraineurs

Frovatriptan is a selective 5-HT(1B/1D) receptor agonist available for acute treatment of migraine in adults (18 years and older). The objective of this study was to determine key pharmacokinetic parameters of frovatriptan in adolescent migraineurs after a single 2.5-mg oral dose and to compare these results with those from an earlier study completed in adults. Subjects were stratified by age (12-14 and 15-17 years) and gender, and serial blood and urine samples were collected over 48 hours. A total of 25 subjects (13 male, 12 female) completed the study. Pharmacokinetic profiles for adolescent subjects were similar to those observed in adults. The median tmax ranged from 2 (male subjects) to 3 (female subjects) hours. The AUC0-24h and Cmax were slightly lower in adolescent subjects as compared with adults. As seen in adults, AUC0-24h and Cmax values were approximately 2-fold higher in females than in their male counterparts (AUC mean range 40.5-59.8 ng x h/mL vs 21.2-23.5 ng x h/mL and Cmax mean range 4.02-6.14 vs ng x h/mL 2.52-2.99 ng/mL, in female and male adolescent subjects, respectively). Elimination was biphasic, with an approximate terminal elimination half-life (t(1/2)) between 12.2 and 25.5 hours. Renal clearance was similar in adolescents and adults, being somewhat higher in female than male subjects. Frovatriptan was well tolerated with no serious or treatment-related adverse effects. In addition, there were no clinically significant changes in safety parameters. Overall, the pharmacokinetic profile of frovatriptan in adolescents (12-17 years) is similar to that seen in adults, and dosing adjustments are unlikely to be needed.

Triptans

Triptans are potent serotonin (5-HT) 1B/1D receptor agonists used to abort and treat migraine headaches. Although the triptans share pharmacodynamic characteristics at 5-HT(1B/1D) receptors, they differ pharmacokinetically. This column reviews how the triptans are metabolized. Generally, the triptans are metabolized by phase I monoamine oxidases (MAOs) and by various cytochrome p450 enzymes. However, each triptan has a unique metabolic profile, leading to significant differences in each triptan's potential for drug-drug interactions. These differences are detailed in this review.

Clinical pharmacokinetics of frovatriptan

OBJECTIVE

To review available data on the clinical pharmacokinetics of frovatriptan.

BACKGROUND

Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from that of the currently available triptans.

METHODS

Studies of healthy volunteers, subjects with renal or hepatic impairment, elderly subjects, and patients with migraine during and between attacks were reviewed.

RESULTS

Oral bioavailability of frovatriptan is 22% to 30%, and although the time to maximum concentration is typically 2 to 3 hours, approximately 60% to 70% of plasma maximum concentration is achieved within 1 hour of dosing. Frovatriptan distributes into erythrocytes, with binding reversible and time dependent. The relatively long terminal elimination half-life (about 26 hours) confers good systemic exposure and may produce a long duration of therapeutic action, thus reducing migraine recurrence and the need for redosing. Systemic exposure to frovatriptan generally correlates with dose between 1 and 100 mg. Blood and plasma frovatriptan concentrations are consistently higher in females, but there is no need to adjust dose according to gender. Pharmacokinetics are essentially unaffected by food and were predictable after repeat dosing; steady state is approached in about 4 to 5 days. Pharmacokinetics were changed only slightly in subjects with renal impairment or mild-to-moderate hepatic impairment, elderly individuals, and during migraine attacks. Frovatriptan is principally metabolized by the CYP1A2 isoenzyme of cytochrome P-450 and is cleared by the kidney and liver, each having sufficient capacity to compensate for impairment of the other.

CONCLUSIONS

Frovatriptan can be taken without regard for food intake, and because of the large therapeutic margin and shallow dose-response curve, there is no need for dosage adjustment in the elderly, in women taking a combined oral contraceptive, in patients with mild-to-severe renal impairment, mild-to-moderate hepatic impairment, or according to gender. The long duration of exposure may reduce the likelihood of early migraine recurrence.

Dose range-finding studies with frovatriptan in the acute treatment of migraine

OBJECTIVE

To determine the optimum dose of frovatriptan for the acute treatment of migraine.

BACKGROUND

Frovatriptan is a new triptan developed for the acute treatment of migraine. The dose-response characteristics and safety of frovatriptan have been investigated across a broad range of doses from 0.5 to 40 mg.

DESIGN

Two randomized, placebo-controlled, double-blind, parallel-group trials, with a total of 1453 patients, were performed to determine the optimal dose of the 5-HT(B/1D)agonist, frovatriptan, for the acute treatment of migraine. The dose ranges studied were 2.5 to 40 mg in the high-dose study and 0.5 to 5 mg in the low-dose study.

RESULTS

At 2 hours postdosing for initial moderate or severe headache (International Headache Society grades 2 or 3), there was an approximate two-fold difference in the proportion of patients taking frovatriptan doses of 2.5 to 40 mg with mild or no headache compared to placebo. Frovatriptan doses of 0.5 mg and 1 mg were not more effective than placebo at 2 hours postdose, and 2.5 mg was identified as the lowest effective dose for the relief of migraine and accompanying symptoms. Above 2.5 mg, no dose-response relationship was observed for any efficacy parameters. There was an increase in the incidence of adverse events from 10 mg and above, but the vast majority were rated as mild in severity and did not impact upon tolerability in a significant manner.

CONCLUSIONS

Frovatriptan was well tolerated throughout the dose range of 0.5 to 40 mg. The 2.5-mg dose confers the optimal balance of efficacy and tolerability for the acute treatment of migraine.

Tolerability and safety of frovatriptan with short- and long-term use for treatment of migraine and in comparison with sumatriptan

OBJECTIVE

To evaluate the tolerability and safety of frovatriptan 2.5 mg in patients with migraine.

BACKGROUND

Frovatriptan is a new, selective serotonin agonist (triptan) developed for the acute treatment of migraine. Dose range-finding studies identified 2.5 mg as the dose that conferred the optimal combination of efficacy and tolerability.

METHODS

The tolerability and safety of frovatriptan 2.5 mg were assessed during controlled, acute migraine treatment studies, including a study that compared frovatriptan 2.5 mg with sumatriptan 100 mg, as well as a 12-month open-label study during which patients could take up to three doses of frovatriptan 2.5 mg within a 24-hour period. Safety and tolerability were assessed through the collection of adverse events, monitoring of heart rate and blood pressure performance of 12-lead electrocardiogram, hematology screen, and blood chemistry studies.

RESULTS

In the short-term studies, 1554 patients took frovatriptan 2.5 mg and 838 took placebo. In the 12-month study, 496 patients treated 13 878 migraine attacks. Frovatriptan was well tolerated in the short- and long-term studies with 1% of patients in the short-term studies and 5% of patients in the long-term study withdrawing due to lack of tolerability. The incidence of adverse events was higher in the frovatriptan-treated patients than in the patients who took placebo (47% versus 34%) and the spectrum of adverse events was similar. When compared to sumatriptan 100 mg, significantly fewer patients taking frovatriptan experienced adverse events (43% versus 36%; P=.03) and the number of adverse events was lower (0.62 versus 0.91), there were also fewer adverse events suggestive of cardiovascular symptoms in the frovatriptan group. Analysis of the entire clinical database (n=2392) demonstrated that frovatriptan was well tolerated by the patients regardless of their age, gender, race, concomitant medication, or the presence of cardiovascular risk factors. No effects of frovatriptan on heart rate, blood pressure, 12-lead electrocardiogram, hematology screen, or blood chemistry were observed. No patient suffered any treatment-related serious adverse event.

CONCLUSIONS

Short- and long-term use of frovatriptan 2.5 mg was well tolerated by a wide variety of patients. Frovatriptan treatment produced an adverse events profile similar to that of placebo, and in a direct comparison study was better tolerated than sumatriptan 100 mg.