available一般表达的含义就是usable或accessible，在这个句子中表达的也是这个含义。
至于如何正确理解这句话的意思应该还是根据上下文来判断。
一般而言，药物代谢的过程应该是这样的。给药后，药物浓度会逐步升高并达到峰值，然后逐步下降。药物作用的强弱一般取决于药物浓度。因此，如此推断的话，这句话想表达的意思也可能是这样的：药物浓度达到峰值后，在药物浓度开始下降的最初一段时间内，希望所给药量中的大部分还继续有效。言下之意，可能希望药物代谢的慢一点以延长药物的作用。
恩，感觉比较有说服力。 哈哈，白马兄，啥个说服力。连蒙带猜瞎闹而已。 今天到国图去借书，顺便把这本书借出来看看：
Modified-Release Drug Delivery Technology. Eds. Michal J. Rathbone, Jonathan Hadgraft and Michael S. Roberts. New York: Marcel Dekker, 2003.
拿到手一看，好大一块砖，上千页。还好很快找到了需要的内容：
Chapter 3
MASRSx and COSRx
Sustained-Release Technology
Syed A. Altaf
David R. Friend
I. Introduction
The advantages of administering a single dose of a drug that is release over an extended period of time, instead of numerous doses, have been obvious to the pharmaceutical industry for some time. The desire to maintain a near-constant or uniform blood level of a drug often translated into better patient compliance, as well as enhanced clinical efficacy of the drug for its intended use.
p21
Guar gum's potential in sustaining the release of water-soluble drugs, such as diltiazem, has recently been published. The advantages of guar gum as a sustained-release excipient are its high viscosity, low cost, and commercial availability.
p22
II Experimental
For guar-gum-based technologies, all the ingredients except magnesium stearate were mixed together in a V-blender for 10 min. ...
For dissolution studies, USP Apparatus II as 50, 100, and 200 rpm paddle speed with simulated gastric fluid (SGF) or simulated instestinal fluid (SIF) was used.
... Clinical studies were performed by Corning Besseluar Clinical Research unit, Madison, WI. The plasma samples were analyzed by Hazelton Wisconsin, Madison, WI.
p22
III MASRx TECHNOLOGY
A.Fomulation Development
The objective was to assess factors affecting drug release from guar-gum-based once-daily matrix sustained-release formulations (MASRTM). In the process, the tablet core expanded and released the drug in a sustained-release manner.
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B. Clinical Evaluations
Three guar-gum-based diltiazem formulations (formulation A, B, and C) were selected for clinical trials along with the reference commercial product, DilacorXR 240 mg. ...
p25
Table 3 Summarizes the pharmacokinetic parameters for the clinical formulations.
Table 3 (Omitted)
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Based on these data, methods were examined to bring the Cmax closer to the reference product in both fasted and fed conditions. First, increasing drug release rate over the first 4-6h followed by a period of slow release compared to reference product (i.e. fast/slow formulation) was hypothesized. In this case, more drug should be available in the early hours following dosing bringing the Cmax down at a later time. The second approach was to decrease the release rate for all time points, i.e., a slower releasing formulation. Based on these two approaches, tow new diltiazem formulations were developed (formulations D, and E, see Table 1). The in vitro dissolution profiles for the two new formulations are shown in Figure 3. The two optimized formulations were evaluated in a second fed and fasted trial.
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有了以上语境，误解那句话的概率会降低很多。我现在的理解如下：
First, increasing drug release rate over the first 4-6h followed by a period of slow release compared to reference product (i.e. fast/slow formulation) was hypothesized. In this case, more drug should be available in the early hours following dosing bringing the Cmax down at a later time.
In this case, more drug should be available/ in the early hours following dosing/ bringing the Cmax down at a later time.
第一种方法是这样设想的，在前4到6小时内增加药物释放率，随后的一段时间缓慢释放，然后与对照组比较（也就是快/慢模式）。在这种情况下，给药早期（数小时内）（体内）有更多的药物可用（即血药浓度更高），这将推迟血药浓度峰值的降低。
当然，非专业人士还是不敢自信。欢迎更多讨论。 Josphe is correct. 引用第22楼白马西北驰于2010-11-12 23:07发表的 :
今天到国图去借书，顺便把这本书借出来看看：
Modified-Release Drug Delivery Technology. Eds. Michal J. Rathbone, Jonathan Hadgraft and Michael S. Roberts. New York: Marcel Dekker, 2003.
.......
厉害厉害，老兄尽然把原文出处给找出来了。 More drug should be available in the early hours following dosing bringing the Cmax down at a later time point.
更多的药在早些时候服用将会导致浓度降低 白马兄真是厉害，居然把原文找出来了。我最近正在看这本书，看得有些吃力啊。
谢谢各位朋友的讨论。 这种氛围就是好啊。
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