Naratriptan pharmacokinetics

CYP1A2 and may therefore be expeeted to have additional interaetions. The picture with zolmitriptan beeomes more eomplieated sinee it is also metabolised by monoamine oxidase A. Naratriptan appears unlikely to undergo significant pharmacokinetic interactions since half the dose is excreted unchanged and the rest metabolised by a variety of isoenzymes. A summary of the metabolic pathways of the triptans can be found in Table 16.2 , (below). 

Although data are limited, the possible small changes in the pharmacokinetics of frovatriptan and naratriptan with smoking are unlikely to be clinically relevant. It should be noted that smoking is a recognised risk factor for cardiovascular disease. Patients with such risk factors should only use the triptans after careful evaluation. 

Oral contraceptives appear to modestly raise the levels of frov-atriptan, naratriptan and zolmitriptan, and slightly increase those of sumatriptan. These changes are not considered clinically significant HRT did not appear to affect the pharmacokinetics of naratriptan. 

Although data are limited, the minor to modest possible ineieases in frov-atriptan, naratriptan, sumatriptan and zoimitriptan pharmacokinetics described are not likely to produce clinically relevant adverse effects. Almotriptan, rizatriptan and sumatriptan do not appear to have any clinically important effect on levels of contraceptive steroids. The significance of the single case report of ischaemic colitis associated with concurrent use of naratriptan and a combined oral contraceptive is unclear. Note that ischaemic colitis has, rarely, been reported with naratriptan itself The manufacturers have found no cases of ischaemic colitis in approximately 450 women on oral contraceptives and taking naratriptan for prophylaxis for 5 to 6 days. However, caution may be needed with concurrent use in those patients with risk factors for ischaemic colitis, such as those with a history of abdominal surgery, low blood pressure, diabetes, cardiovascular disease or stroke. 

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