Maximum plasma concentration

These effects could result from the progression of the disease but as they are a feature of levodopa therapy a change in the central response to levodopa or changes in its peripheral kinetics are more likely. The latter does not occur since the maximum plasma concentration, the time to reach it and the plasma half-life are still similar after 10 years of treatment to those achieved initially, although continuous infusion of dopa can smooth out the swings. 

When 100 mg of synthetic astaxanthin in olive-oil-containing meal was given to male volunteers, a maximum plasma concentration of 1.24 mg/L astaxanthin was observed in the first 6 hours postprandially. The relative concentration of total astaxanthin in HDL decreased compared to the other lipoprotein fractions in the 72-hour study. 

Letrozole is another selective aromatase that inhibits the conversion of androgens to estrogen. Maximum plasma concentrations occur 1 hour after oral dosing concomitant food has not been shown to have an effect on the extent of absorption of letrazole. The terminal half-life is approximately 2 days. Letrozole is used in the treatment of postmenopausal women with hormone-receptor-positive or unknown advanced breast cancer. Side effects include bone pain, hot flushes, back pain, nausea, arthralgia, osteoporosis/bone fractures, and dyspnea. 

BPH—benign prostatic hypertrophy BPM—breaths per minute beats per minute BUN—blood urea nitrogen C—mean plasma concentration Cmi]X—maximum plasma concentration Cmm—minimum plasma concentration C albicans—Candida albicans C. bofulinum—Clostridium frotu/irtum C. difficile—Clostridium difficile C. jejuni—Campylobacter jejuni C. neoformans—Cryptococcus neoformans Ca—calcium... 

Cmax- maximum plasma concentration C, minimum plasma concentration F, bioavailability t elimination half-life. 

Some idea of the rate of absorption can be obtained from examination of the plasma concentration-time profile. It should be remembered, however, that the time to maximum plasma concentration Y ) is not when absorption is complete but when the rates of drug absorption and elimination are equal. Thus two drugs with the same absorption rate will differ in /max if elimination rates differ. Assessment of the rate of absorption can also be confounded by complex or slow drug distribution. For example, the calcium-channel blocker amlodipine has a much later /max than other similar drugs. This is not due to slow absorption but to partitioning in the liver membrane with slow redistribution. A quantitative assessment of the rate of absorption can be obtained by deconvolution of plasma profiles following IV and oral administration. 

Maximum plasma concentration, CmaK, is a measure of both the rate and extent of drug absorption. It is also an essential component of the bioavailability... 

The steady-state maximum plasma concentration, Cmaxss, of gentamycin and tobramycin are 6 to 10 mcg/mL. The Cmax ss of amikacin is 25 to 30 mcg/mL. The Cmin ss of both gentamycin and tobramycin is 0.5 to 1.5 mcg/mL, while that of amikacin is 5 to 8 mcg/mL. In order for these drugs to be effective, it is important to closely monitor their therapeutic concentrations. An important observation of these antibiotics is that with prolonged therapy, the Cminsl, values increase. This increase is due to the renal impairment. In the case where Cmin ss is less than the desired Cmin ss, the dose may be insufficient. 

PK For therapeutic range of 0.45. 5 tg/kg, maximum plasma concentration, half-life, and AUC are linear with respect to dose. Following subcutaneous injection, the absorption is slow and rate limiting. The half-life ranges from 27 to 89 hours. Peak plasma concentration is 34 hours after subcutaneous (SC) administration for CRF patients and 90 hours for cancer patients. 

Commercial samples containing approximately 400 mg of ephedra per capsule yield roughly 5 mg of ephedrine, 1 mg of pseudoephedrine, and less than 1 mg of methylephedrine (White et al. 1997). For a dose of four capsules, yielding approximately 20 mg of ephedrine, the elimination half-life is 5.2 hours. The time to reach maxium concentration is 3.9 hours. Compared to pure ephedrine tablets, the elimination kinetics of ephedra are comparable. However, ephedra showed somewhat different absorption kinetics (e.g., lag time, area under the concentration-time curve, and maximum plasma concentration). So, ephedra tablets may vary from pure ephedrine in the onset of action, but the durations of action are grossly equivalent. 

All the above mentioned polymers have been evaluated mainly for application in the intestine. Finally, the last part of the gastrointestinal tract, the rectum should also be mentioned as a suitable site for delivery and fast absorption of therapeutics. Kim et al. [88] developed an in situ gelling and mucoadhesive acetaminophen liquid suppository prepared with poloxamers and sodium alginate. It was found that this particular formulation of acetaminophen in humans resulted in shorter T ax and higher maximum plasma concentrations of dmg (C ax) than the conventional acetaminophen suppositories. 

Most physicians will be familiar with the basic shape of a plasma concentration-time curve following oral or intravenous administration, and they are likely to be familiar with, or at least readily imderstand, the simple terms that relate to this shape. Such terms - (1) maximum plasma concentration (Cmax). (2) time to maximum plasma concentration (fmax), (3) area under the plasma concentration-time curve (AUC) and (4) half-life (fi/2) - are illustrated in Figure 5.2. 

Absorption - Nalmefene is completely bioavailable following IM or subcutaneous administration. Nalmefene will be administered primarily as an IV bolus however, it can be given IM or subcutaneous if venous access cannot be established. While the time to maximum plasma concentration was 2.3 hours following IM and 1.5 hours following subcutaneous administrations, therapeutic plasma concentrations are likely to be reached within 5 to 15 minutes after a 1 mg dose in an emergency. 

Absorption - Following oral administration, amiodarone is slowly and variably absorbed bioavailability is approximately 50%. Maximum plasma concentrations are attained 3 to 7 hours after a single dose. Plasma concentrations with chronic dosing at 100 to 600 mg/day are approximately dose-proportional, with a mean 0.5 mg/L increase for each 100 mg/day. 

Elderly Following administration of single (300 mg) and multiple (600 mg/day) doses of oxcarbazepine to elderly volunteers (60 to 82 years of age), the maximum plasma concentrations and AUC values of MHD were 30% to 60% higher than in younger volunteers (18 to 32 years of age). 

Absorption/Distribution - Selegiline is rapidly absorbed approximately 73% of a dose is absorbed maximum plasma concentration occurs 0.5 to 2 hours following administration. 

Pharmacokinetics Disulfiram is slowly absorbed from the Gl tract and eliminated slowly from the body. The average time to reach maximum plasma concentrations... 

Drug/Food interactions Maximum plasma concentrations of misoprostol acid are diminished when taken with food. 

HIV-infected patients administered saquinavir mesylate (600 mg 3 times daily) had area under the curve (ADC) and maximum plasma concentration (Cmax) values approximately 2 to 2.5 times those observed in healthy... 

Effect of food Maximum plasma concentrations and area under the plasma concentration-time curve (AUC) were 2- to 3-fold higher underfed conditions compared with fasting. 

Absorption/Distribution Following oral administration to HIV-infected patients, the mean absolute bioavailability of zalcitabine was greater than 80%. The absorption rate of a 1.5 mg oral dose was reduced when administered with food. This resulted in a 39% decrease in mean maximum plasma concentrations (Cmax) 25.2 to 15.5 ng/mL, and a 2-fold increase in time to achieve Cmaxfro mean of 0.8 hours under fasting conditions to 1.6 hours when the drug was given with food. The extent of absorption was decreased by 14% (from 72 to 62 ng h/mL). 

Pharmacokinetics The absolute bioavailability after a 70 mg subcutaneous bolus injection in healthy subjects (n = 11) is 95%. In subjects with RA, maximum plasma concentrations occurred 3 to 7 hours after subcutaneous administration of anakinra at clinically relevant doses (1 to 2 mg/kg n = 18) the terminal half-life ranged from 4 to 6 hours. In RA patients, no unexpected accumulation was observed after daily subcutaneous doses for up to 24 weeks. The estimated clearance increased with increasing Ccr and body weight. 

Anastrozole is well absorbed following oral administration. The maximum plasma concentration of the drug occurs at 2 h from dosing, that is, C ax = 2 h. It is cleared slowly, with a half-life of 30-50 h. The drug is metabolized extensively and only 10% of the drug is excreted in urine as the unchanged drug. 

In terms of pharmacokinetics, letrozole is well absorbed following 2.5-mg oral administration in healthy postmenopausal women. The maximum plasma concentration of... 

Dasatinib is an oral dual BCR/ABL and Src family tyrosine kinases inhibitor approved for use in patients with chronic myelogenous leukemia after ima-tinib treatment and for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia. Maximum plasma concentrations (Cmax) of dasatinib are observed between 0.5 and 6 hours (Tmax) following oral administration. Dasatinib is extensively metabolized in humans, primarily by the cytochrome P450 enzyme 3A4. CYP3A4 was the primary enzyme responsible for the formation of the active metabolite. The overall mean terminal half-life of dasatinib is 3-5 hours. Adverse events included mild to moderate diarrhea, peripheral edema, and headache. Neutropenia and myelosuppression were common toxic effects. 

For some agents for example valproic acid and ethanol, a threshold concentration must be reached before teratogenicity is induced and the effect is therefore related to the maximum plasma concentration For others such as retinoids and cyclophos-... 

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