資料來源：Zekerie Redzheb / 2023 年 6 月 / aidsmap / 財團法人台灣紅絲帶基金會編譯
馬雷克•金舍 | Mareike Günsche www.aspect-us.com
對於許多人來說，抗反轉錄病毒治療已將愛滋病毒徹底轉變為易於控制的疾病。 然而，如果您感染了愛滋病毒，您需要按照處方服藥，以完全控制病毒並防止其損害您的健康。 與需要每天在同一時間服用的舊藥物不同，新藥物更加「寬容」。 雖然您應該每天服用它們，但對於大多數人來說，您不必擔心會有點晚。
大多數愛滋病毒藥物遵循特定的吸收途徑（身體吸收藥物的方式）和消除途徑（身體清除藥物的方式）。 藥丸通常在小腸中吸收，並通過肝臟和/或腎臟消除。 這些器官的健康狀況以及我們的基因構成可能會導致吸收和消除率發生一些變化。 儘管如此，推薦的標準劑量應該克服體內藥物有效量的個體差異。 此外，一些藥物、草藥和替代療法以及娛樂性藥物可以對愛滋病毒藥物的吸收和消除產生更明顯的影響。 有時它們會導致藥物濃度達到危險的高水平或無效的低水平。
不同的藥物有不同的吸收和消除時間和速率，這兩個變量決定了藥物在體內停留的時間。 半衰期是用於描述物質在系統中停留時間的單位。 例如，如果藥物的半衰期為五個小時，那麼您的身體將需要五個小時才能將其濃度降低一半。 大多數藥物需要五個半衰期才能完全消除，因此我們的示例藥物需要 25 小時才能完全消除。
儘管與半衰期有關，愛滋病毒藥物的另一個重要方面是它們在系統中維持有效濃度的時間。 每種藥物必須在體內達到特定的最低有效濃度（MEC），在該濃度下，它可以充分防禦病毒並將耐藥風險降至最低。 換句話說，即使藥物的半衰期很長，它仍然可能相對較快地達到低於 MEC 的水平，從而不再有效。 所有 HIV 藥物的設計目的都是在您下一次服藥之前維持遠高於 MEC 的水平 – 藥物降至 MEC 以下所需的時間比建議的服藥間隔時間長。
HIV 藥物還具有抵抗障礙的特點。 該術語用於解釋如果錯過劑量，病毒對給定藥物產生耐藥性的速度有多快。 幸運的是，許多新藥比舊藥具有更高的耐藥屏障。 藥物的耐藥屏障取決於它阻斷病毒生命週期的哪一步、其靶點（是否與病毒上非常重要的位置結合）及其結合強度（藥物與其靶點結合的強度）。 具有高耐藥屏障的藥物將與病毒的重要部位結合，沒有該部位病毒就無法繁殖。 它還會非常牢固地結合，因此病毒無法逃脫，如果病毒試圖改變該部分（突變）以逃脫，這將對病毒有害。
藥物的所有上述特徵可以綜合起來評估藥物的「寬恕性」。 寬恕是一個概念，有助於理解您需要多麼嚴格地按時服藥。 服用更寬容的藥物可以最大限度地減少出現不良後果的可能性，例如藥物濃度低、耐藥性和治療失敗等。 比給藥時間晚得多且具有高耐藥屏障的藥物比在下一個給藥時間左右降至 MEC 以下且具有低耐藥屏障的藥物更容易被接受。 較新的愛滋病毒藥物通常比較舊的藥物更寬容，因此單次漏服很少會導致治療失敗，但多次漏服會顯著增加風險。
上述結論的一個例外是長效注射製劑。 雖然作為藥物，它們遵循迄今為止描述的大多數特徵，但它們不同的遞送方式（非口服）和體內釋放（較慢）顯著改變了它們的動力學。 它們的給藥間隔很長，從幾周到幾個月不等，使得單次錯過劑量非常令人擔憂和危險。
此頁面的上次審核時間為 2023 年 6 月。審核截止日期為 2026 年 6 月。
What happens to HIV drugs in the body, and do missed doses matter?
Zekerie Redzheb / June 2023 / aidsmap
Mareike Günsche | www.aspect-us.com
Antiretroviral therapy has completely transformed HIV into an easily manageable condition for many
people. However, if you are living with HIV, you need to take your medication as prescribed in order to fully control the virus and prevent it from damaging your health. Unlike older drugs that needed to be taken at exactly the same time each day, newer medications are more ‘forgiving’. While you should aim to take
them every day, for most you do not need to worry about being a bit late.
Most HIV drugs follow specific pathways of absorption (the way the body absorbs the drug)
and elimination (the way the body removes the drug). Pills are usually absorbed in the small intestine and elimination could happen via the liver and/or the kidneys. The health of these organs as well as our genetic make-up can lead to some variation in the rates of absorption and elimination. Nonetheless, the standard dosages that are recommended should overcome individual variation in the effective amount of drug
present in the body. Additionally, some medicines, herbal and alternative treatments, and recreational drugs can have a more pronounced effect on the absorption and elimination of the HIV drugs. Sometimes they can lead to dangerously high or ineffectively low levels of the drug.
Different drugs have varying times and rates of absorption and elimination, and these two variables
determine how long the drug stays in the body. Half-life is the unit used to describe how long a substance stays in the system. If a drug has a half-life of five hours for example, it will require five hours for your body to reduce its concentration by half. Most drugs require five half-lives for complete elimination, so our
example drug will take 25 hours before it’s fully eliminated.
Although related to the half-life, another essential aspect of HIV drugs is how long they maintain effective concentrations in the system. Each drug has to reach a specific minimal effective concentration (MEC) in the body at which it is fully protective against the virus and minimises the risk of resistance. In other words, even if a drug has a very long half-life, it may still reach levels below MEC relatively quickly and no longer be effective. All HIV drugs are designed to maintain levels much higher than MEC until your next dose – the
time it takes the drug to fall below MEC is longer than the recommended time between doses.
HIV drugs are also characterised by a barrier to resistance. This term is used to explain how quickly the
virus can become resistant to a given drug if doses are missed. Fortunately, many of the newer drugs have a higher barrier to resistance than older drugs. The resistance barrier of a drug depends on which step of the virus’ lifecycle it blocks, its target (whether it binds to a very vital place on the virus or not) and its binding strength (how strongly the drug binds to its target). A drug with a high barrier to resistance will bind to a
vital place on the virus without which the virus cannot multiply. It will also bind very strongly, so the virus cannot escape and if the virus tries to change that part (mutate) in order to escape, that will be detrimental for the virus.
All of the above characteristics of drugs can be put together to assess a drug’s ‘forgiveness’. Forgiveness is a concept that helps understand how strict you need to be about taking your medication on time. Taking a more forgiving drug minimises the chance of unwanted outcomes, such as ineffectively low drug levels,
resistance and treatment failure. A drug that falls below MEC much later than its dosing time and has a high barrier to resistance will be more forgiving than a drug that falls below MEC around the next dosing time and has a low barrier to resistance. The newer HIV drugs are generally more forgiving than the older ones, so a single missed dose is rarely a cause of treatment failure – but repeatedly missed doses can significantly raise the risk.
One exception to the above conclusion are the long-acting injectable formulations. While, as drugs, they obey most characteristics described so far, their different mode of delivery (non-oral) and release in the body (slower) significantly change their dynamics. Their very long dosing intervals, ranging from weeks to months, make a single missed dose very concerning and risky.
This page was last reviewed in June 2023. It is due for review in June 2026.