Almotriptan: a review of its use in migraine

Tandem construction of biological relevant aliphatic 5-membered N-heterocycles

Nature often uses cascade reactions in a highly stereocontrolled manner for assembly structurally diverse nitrogen-containing heterocyclic scaffolds, i.e. secondary metabolites, important for medicinal chemistry and pharmacy. Five-membered nitrogen-containing heterocycles as standalone rings, as well as spiro and polycyclic systems are pharmacophores of drugs approved in various therapies, i.a. antibacterial or antiviral, antifungal, anticancer, antidiabetic, as they target many key enzymes. Furthermore, a large number of pyrrolidine derivatives are currently considered as drug candidates. Cascade transformations, also known as domino or tandem reactions, offer straightforward methods to build N-heterocyclic libraries of the great structural variety desired for drawing SAR conclusions. The tandem transformations are often atom economic and time-saving because they are performed as the one-pot, so no need for purification after each 'virtual' step and the limited necessity of protective groups are characteristic for these processes. Thus, the same results as in classical multistep synthesis can be achieved at markedly lower costs and shorter time, which is in line with modern green chemistry rules. Great advantage of cascade reactions is often reflected in their high regio- and stereoselectivities, enabling the preparing of the heterocyclic compound better fitted to the expected target in cells. This review reveals the biological relevance of N-heterocyclic scaffolds based on saturated 5-membered rings since we showed a number of examples of approved drugs together with the recent biologically attractive leading structures of drug candidates. Next, novel cascade synthetic procedures, taking into account the structure of the reactants and reaction mechanisms, enabling to obtain biological-relevant heterocyclic frameworks with good yields and relatively high stereoselectivity, were reviewed and compared. The review covers the advances of designing biological active N-heterocycles mainly from 2018 to 2021, whereas the synthetic part is focused on the last 7 years.

Pharmacological strategies to treat attacks of episodic migraine in adults

INTRODUCTION

Migraine patients prioritize early complete relief of headache and associated symptoms, sustained freedom of pain, and good tolerability. One major obstacle for the successful use of drug treatment of migraine attack is that the speed of action of triptans, 5-HT_1B/1D receptor agonists, is delayed.

AREAS COVERED

In this review, the author discusses the following features of acute migraine drugs: pharmacology; pharmacokinetics, and absorption of drugs during migraine attacks. Next, dose-response curves for effect; and the delayed onset of action is reviewed. In the more clinical part of the review, the following items are discussed: overall clinical judgments; comparison of triptans; comparison of triptans with NSAIDs; early intervention with triptans; medication-overuse headache; comments on the effect of gepants; and the general principle of acute migraine therapy.

EXPERT OPINION

The delay in the onset of effect of acute migraine drugs is likely due to a complex antimigraine system involving more than one site of action. Investigations into the mechanisms of the delay should have a high priority, both in studies with animals, migraine models, and in migraine patients during attacks. Non-oral administration of antimigraine drugs resulting in early absorption of drugs should be developed as they possibly also can increase E_max.

One-Pot Synthesis of Indole-3-acetic Acid Derivatives through the Cascade Tsuji-Trost Reaction and Heck Coupling

A practical palladium-mediated cascade Tsuji-Trost reaction/Heck coupling of N-Ts o-bromoanilines with 4-acetoxy-2-butenonic acid derivatives using a Pd(OAc)₂/P( o-tol)₃/DIPEA system is described for a straightforward synthesis of indole-3-acetic acid derivatives. This methodology was successfully applied to synthesize various substituted indole/azaindole-3-acetic acid derivatives and Almotriptan, which is a drug for the acute treatment of migraines. Moreover, a plausible cyclization mechanism has been proposed.

Why pharmacokinetic differences among oral triptans have little clinical importance: a comment

Triptans, selective 5-HT1B/1D receptor agonists, are specific drugs for the acute treatment of migraine that have the same mechanism of action. Here, it is discussed why the differences among kinetic parameters of oral triptans have proved not to be very important in clinical practice. There are three main reasons: (1) the differences among the kinetic parameters of oral triptans are smaller than what appears from their average values; (2) there is a large inter-subject, gender-dependent, and intra-subject (outside/during the attack) variability of kinetic parameters related to the rate and extent of absorption, i.e., those which are considered as critical for the response; (3) no dose-concentration–response curves have been defined and it is, therefore, impossible both to compare the kinetics of triptans, and to verify the objective importance of kinetic differences; (4) the importance of kinetic differences is outweighed by non-kinetic factors of variability of response to triptans. If no oral formulations are found that can allow more predictable pharmacokinetics, the same problems will probably also arise with new classes of drugs for the acute treatment of migraine.

Pharmacogenomics and migraine: possible implications

Pharmacogenomics is the science about how inherited factors influence the effects of drugs. Drug response is always a result of mutually interacting genes with important modifications from environmental and constitutional factors. Based on the genetic variability of pharmacokinetic and in some cases pharmacodynamic variability we mention possible implications for the acute and preventive treatment of migraine. Pharmacogenomics will most likely in the future be one part of our therapeutic armamentarium and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution.

Clinical Pharmacokinetics of Almotriptan, a Serotonin 5-HT1B/1D Receptor Agonist for the Treatment of Migraine

The pharmacokinetics of almotriptan are linear over a range of oral doses up to 200mg in healthy volunteers. The compound has a half-life of approximately 3 hours. Almotriptan is well absorbed after oral administration and the mean absolute bioavailability is 69.1%. Maximal plasma concentrations are achieved between 1.5 and 4 hours after dose administration; however, within 1 hour after administration, plasma concentrations are approximately 68% of the value at 3 hours after administration. Food does not significantly affect almotriptan absorption. Almotriptan is not highly protein bound and is extensively distributed in the body. Approximately 50% of an almotriptan dose is excreted unchanged in the urine; this is the predominant single mechanism of elimination. Renal clearance is mediated, in part, through active tubular secretion, while the balance of the almotriptan dose is metabolised to inactive compounds. The predominant route of metabolism is via monoamine oxidase-A, and cytochrome P450 (CYP) mediated oxidation (via CYP3A4 and CYP2D6) occurs to a minor extent. Almotriptan clearance is moderately reduced in elderly subjects, but the magnitude of this effect does not warrant a dose reduction. Sex has no significant effect on almotriptan pharmacokinetics. Almotriptan pharmacokinetic parameters do not differ between adolescents and adults, and absorption is not affected during a migraine attack. As expected, renal dysfunction results in reduced clearance of almotriptan. Patients with moderate-to-severe renal dysfunction should use the lowest dose of almotriptan and the total daily dose should not exceed 12.5 mg. Similar dosage recommendations are valid for patients with hepatic impairment, based on the clearance mechanisms for almotriptan. Drug-drug interaction studies were conducted between almotriptan and the following compounds: fluoxetine, moclobemide, propranolol, verapamil and ketoconazole. No significant pharmacokinetic or pharmacodynamic interactions with almotriptan were observed for fluoxetine or propranolol. Almotriptan clearance was reduced, to a modest degree, by moclobemide and verapamil, which was consistent with the contribution of monoamine oxidase-A and CYP3A4 to the metabolic clearance of almotriptan. Although ketoconazole has a greater effect on almotriptan clearance than verapamil, no dosage adjustment is required when almotriptan is given with these drugs.

Interaction between ketoconazole and almotriptan in healthy volunteers

The interaction between almotriptan, a 5-HT1B/1D agonist, and the potent CYP3A4 inhibitor ketoconazole was examined in 16 healthy volunteers. Subjects received (A) 12.5 mg almotriptan orally on Day 2 of a 3-day regimen of 400 mg ketoconazole once daily and (B) 12.5 mg almotriptan in a crossover design. Plasma and urine concentrations of almotriptan were measured by HPLC. Treatment effects on almotriptan pharmacokinetics were assessed by analysis of variance. Ketoconazole coadministration increased mean almotriptan AUC and Cmax from 312 to 490 ng h/mL and 52.6 to 84.5 ng/mL, respectively. Mean oral clearance was decreased from 40.7 to 26.2 L/h by ketoconazole, with an accompanying increase in the fraction of almotriptan excreted unchanged in the urine (40.6% to 53.3%) and a decrease in renal clearance (16.4 to 13.8 L/h). These effects were statistically significant. The effects of ketoconazole on almotriptan clearance were consistent with inhibition of the CYP3A4-mediated metabolism and a slight effect on the active tubular secretion of almotriptan.

Absolute bioavailability, pharmacokinetics, and urinary excretion of the novel antimigraine agent almotriptan in healthy male volunteers

Absolute bioavailability, pharmacokinetics, and urinary excretion of almotriptan, a novel 5-HT(1B/1D) receptor agonist, were studied in 18 healthy males following single intravenous (i.v.) (3 mg), subcutaneous (s.c.) (6 mg), and oral (25 mg) doses. Volunteers received each dose in a randomized sequence separated by a 7-day washout. Blood and urine samples for pharmacokinetic evaluations were taken for up to 24 hours after dosing. The disposition kinetics of almotriptan after i.v. and s.c. administration showed biphasic decline described by a two-compartment model. The fastest disposition phase was well observed, although estimates of the rate constant showed high variability. After s.c. administration of almotriptan, the bioavailability was 100% with a time to maximum plasma concentration (tmax) of 5 to 15 minutes, whereas after oral administration, the bioavailability was about 70% with a tmax of 1.5 to 3.0 hours. No significant differences were observed between administration routes in the elimination half-life (t(1/2), obtaining mean values ranging from 3.4 to 3.6 hours. The volume of distribution, total clearance, and t(1/2) indicated that almotriptan was extensively distributed and rapidly cleared from the body irrespective of dose or route of administration. The primary route of elimination was renal clearance (approximately 50%-60% of total body clearance). About 65% of the i.v. and s.c. dose and 45% of the oral dose were excreted unchanged in urine in 24 hours, with nearly 90% of this in the first 12 hours. Renal clearance was approximately 2- to 3-fold that of the glomerular filtration rate in man, suggesting that almotriptan is eliminated in part by renal tubular secretion.

Rizatriptan: an update of its use in the management of migraine

Rizatriptan is an orally active serotonin 5-HT(1) receptor agonist that potently and selectively binds to 5-HT(1B/1D) subtypes. Earlier clinical trials demonstrated that rizatriptan 5 or 10mg is more effective than placebo at providing pain relief and a pain-free state, relieving associated symptoms of migraine, normalising functional ability and improving patient quality of life, and showed that rizatriptan provides faster freedom from pain and reduces nausea to a greater extent than oral sumatriptan. More recently, rizatriptan 10mg was shown to be more effective than zolmitriptan 2.5mg or naratriptan 2.5mg at producing a pain-free state 2 hours postdose. Furthermore, compared with naratriptan, significantly more patients who received rizatriptan were pain free or had pain relief from 1 hour onwards. The number of patients with normal functional ability at 2 hours was significantly higher after rizatriptan than after naratriptan or zolmitriptan. Rizatriptan was also generally more effective than zolmitriptan or naratriptan at relieving migraine-associated symptoms. Rizatriptan is generally well tolerated and adverse events are usually mild and transient. The most common adverse events associated with rizatriptan in recent randomised trials were asthenia/fatigue, dizziness, somnolence and nausea. There was a trend towards a lower incidence of adverse events with rizatriptan compared with zolmitriptan (31.2 vs 38.8%). However, rizatriptan was associated with a significantly higher incidence of adverse events than naratriptan (39 vs 29%). The incidence of chest pain was similar after the administration of rizatriptan, zolmitriptan or naratriptan (2 to 4%).

CONCLUSION

Rizatriptan is an effective drug for the acute treatment of moderate or severe migraine. Oral rizatriptan 5 and 10mg have shown greater efficacy than placebo in providing pain relief, an absence of pain, relief from associated symptoms, normal functional ability and an improvement in patient quality of life. Earlier results showed that rizatriptan provides faster freedom from pain and reduces nausea to a greater extent than oral sumatriptan. More recent studies have shown that rizatriptan 10mg provides faster pain relief and a higher percentage of patients with an absence of pain and normal functional ability at 2 hours than naratriptan 2.5mg or zolmitriptan 2.5mg. The efficacy of rizatriptan is retained when used in the long term and the drug is generally well tolerated. Although well designed studies comparing rizatriptan with almotriptan, eletriptan and frovatriptan would further define the position of rizatriptan, current data suggest rizatriptan should be considered as a first-line treatment option in the management of migraine.