Have you ever wondered what happens to a painkiller, like ibuprofen, after you swallow it? Medicine that slides down your throat can help treat a headache, a sore back, or a throbbing sprained ankle. But how does it get where it needs to go in the first place? The answer is that it hitches a ride in your circulatory blood stream, cycling through your body in a race to do its job before it's snared by organs and molecules designed to neutralize and expel foreign substances. This process starts in your digestive system. Say you swallow an ibuprofen tablet for a sore ankle. Within minutes, the tablet starts disintegrating in the acidic fluids of your stomach. The dissolved ibuprofen travels into the small intestine and then across the intestinal wall into a network of blood vessels. These blood vessels feed into a vein, which carries the blood, and anything in it, to the liver. The next step is to make it through the liver. As the blood and the drug molecules in it travel through liver blood vessels, enzymes attempt to react with the ibuprofen molecules to neutralize them. The damaged ibuprofen molecules, called metabolites, may no longer be effective as painkillers. At this stage, most of the ibuprofen makes it through the liver unscathed. It continues its journey out of the liver, through veins, into the body's circulatory system. Half an hour after you swallow the pill, some of the dose has already made it into the circulatory blood stream. This blood loop travels through every limb and organ, including the heart, brain, kidneys, and back through the liver. When ibuprofen molecules encounter a location where the body's pain response is in full swing, they bind to specific target molecules that are a part of that reaction. Painkillers, like ibuprofen, block the production of compounds that help the body transmit pain signals. As more drug molecules accumulate, the pain-cancelling affect increases, reaching a maximum within about one or two hours. Then the body starts efficiently eliminating ibuprofen, with the blood dose decreasing by half every two hours on average. When the ibuprofen molecules detach from their targets, the systemic blood stream carries them away again. Back in the liver, another small fraction of the total amount of the drug gets transformed into metabolites, which are eventually filtered out by the kidneys in the urine. The loop from liver to body to kidneys continues at a rate of about one blood cycle per minute, with a little more of the drug neutralized and filtered out in each cycle. These basic steps are the same for any drug that you take orally, but the speed of the process and the amount of medicine that makes it into your blood stream varies based on drug, person, and how it gets into the body. The dosing instructions on medicine labels can help, but they're averages based on a sample population that doesn't represent every consumer. And getting the dose right is important. If it's too low, the medicine won't do its job. If it's too high, the drug and its metabolites can be toxic. That's true of any drug. One of the hardest groups of patients to get the right dosage for are children. That's because how they process medicine changes quickly, as do their bodies. For instance, the level of liver enzymes that neutralize medication highly fluctuates during infancy and childhood. And that's just one of many complicating factors. Genetics, age, diet, disease, and even pregnancy influence the body's efficiency of processing medicine. Some day, routine DNA tests may be able to dial in the precise dose of medicine personalized to your liver efficiency and other factors, but in the meantime, your best bet is reading the label or consulting your doctor or pharmacist, and taking the recommended amounts with the recommended timing.
你是否曾想過 當你吞下止痛藥,像是布洛芬 它會發生什麼變化呢? 從喉嚨滑下的藥物 會幫你治療頭痛 背痛 或腳踝扭傷的抽痛 但首先它是如何到達 需要去的地方呢? 答案是藥物會藉由循環血流的運送 在體內循環並快速發揮作用 直到被器官攫取 且分子被分解失效 然後把外來物排出 這個過程始於你的消化系統 當你因為腳踝痠痛吞下布洛芬錠 幾分鐘內藥物開始被胃中的胃酸分解 被溶解的布洛芬進入小腸 然後通過腸壁進入血管網絡 這些血管注入一條靜脈(肝門靜脈) 它運送血液及其內含物進入肝臟 下一步是通過肝臟 當血液和藥物分子行經肝臟血管 酵素會試圖與布洛芬產生反應 使之失去作用 損壞的布洛芬分子稱為「代謝物」 就不再具有止痛藥的作用 在此階段,大部分的布洛芬 都能安然通過肝臟 它會經由靜脈繼續離開肝臟 進入身體的循環系統 在你吞下藥物的半小時後 一些藥物已經進入循環血流內 這些血液管路通過四肢和器官 包括心臟、腦、腎臟 然後返回肝臟 當布洛芬分子來到 身體疼痛非常強烈的地方 它們會與反應中的特定目標分子結合 像布洛芬的止痛藥會阻斷 協助傳送疼痛訊號的複合物之製造 當越多藥物分子積聚 止痛的藥效也會隨之增加 一到兩小時內會達到最大的效果 然後,身體開始有效率地清除布洛芬 平均每兩小時 血中藥的濃度減半 當布洛芬分子與特定目標分子分離 血液系統也會再次將布洛芬分子帶走 回到肝臟後 又有藥物總量的一小部分 被轉換成代謝物 最後由腎臟濾出到尿液 從肝到身體到腎的環路 以約每分鐘血循環一次的速度進行 每次循環就有部分藥物 被分解失效且排出 任何口服藥物都是同樣的循環方式 但其運作的速度 以及進入血液的藥物劑量 則會因為藥物 人 和進入身體的方式而不同 藥物標籤上的劑量指示會有助益 但它們通常是以 抽樣人口的平均值為基準 並非每位使用者均適用 使用正確的藥物劑量很重要 劑量太低,藥物不會發揮功效 劑量太高,藥物及其代謝物是有害的 任何藥物都是如此 最難掌控正確劑量的 病人群之一是小孩 那是因為他們處理藥物變化迅速 正如他們身體一樣 例如,代謝藥物的肝臟酵素濃度 在嬰幼兒時期起伏很大 這只是許多複雜原因的其中之一 基因 年齡 飲食習慣 疾病 甚至懷孕都會影響代謝藥物的效率 未來,或許例行基因檢測 能依個人肝臟效能與其他因素 而精準算出藥物使用劑量 但在此其間 最好還是詳閱藥物的標籤 或者詢問你的醫師或藥師 在對的時間用適當劑量的藥物