Re: Imitrex(Sumatriptan) Sumatriptan is a blocker of 5-HT (Serotonin) receptors. It is marketed solely for the treatment of migraine headache. It is not an analgesic, rather it produces a rapid vasoconstriction in various regions of the brain, thus reducing the cause of migraines. The only data available is from the pharmaceutical company. It is available in oral tablets and an injectible for subcutaneous injection. The plasma half-life is rather short ( about 2.5 hrs). It has a high volume of distribution, which means that the drug rapidly enters the bloodstream and then exits to other periheral compartments. Therefore, the plasma level is somewhat small. In studies with rodents(rats), the milk:plasma ratios are quite high, from about 6.3 at 1 hour to 7.8 at 4 hours(IV injection). Sumatriptan is apparently ion trapped in in milk. At 24 hours the drug is undetectible in milk and plasma. However, although the M:P ratio is high, the actual amount of drug present in milk was quite small, 268 ng/ml at one hour, 114 ng/ml at 1.2 hrs, thus suggesting that the large volume of distribution of this drug sequesters most of it in peripheral compartments, not the plasma compartment which feeds the milk compartment. Another good piece of info is that the oral bioavailability of this product is poor, averaging only 15%. Hence infant absorption would be greatly limited. The oral dose in adults is 25 mg. An infant would have to drink 94 liters of milk per day, to get an adult dose of 25 mg(assuming this rat data is close to human data). As we know, the side effects are minimal, and include tingling, and hot sensations. The pharmaceutical company routinely recommends a 24 cessation of breastfeeding after taking the medication. We do not have any pediatric data concerning kinetics, absorption, etc. Tom Hale