How long do the minor side effects of rectiv last once applied? mainly minor headache

Depending on amount: Fortunately the half-life of this medicine is quite short 2-3 min, meaning half of the amount is gone in 2-3 min once absorbed into your body. Thus, the duration of side effect such as headache depends on how much you used. The formulation also affects this--since not all is absorbed at once, the effect will likely last much longer...an hour or two? Tylenol (acetaminophen) may help. Good luck