Continuous intravenous infusion

One-compartment open model for continuous intravenous infusion... 

In the previous discussion of the one- and two-compartment models we have loaded the system with a single-dose D at time zero, and subsequently we observed its transient response until a steady state was reached. It has been shown that an analysis of the response in the central plasma compartment allows to estimate the transfer constants of the system. Once the transfer constants have been established, it is possible to study the behaviour of the model with different types of input functions. The case when the input is delivered at a constant rate during a certain time interval is of special importance. It applies when a drug is delivered by continuous intravenous infusion. We assume that an amount Z) of a drug is delivered during the time of infusion x at a constant rate (Fig. 39.10). The first part of the mass balance differential equation for this one-compartment open system, for times t between 0 and x, is given by ... 

Fig. 39.10. (a) One-compartment open model for continuous intravenous infusion of a dose D from a reservoir. The rate of infusion is k. (b) Time courses of the content in the reservoir Xn of the plasma concentration Cp and of the content of the elimination pool... 

In the limit, when the interval 0 between administrations becomes extremely small in comparison with the elimination half-life 0.693/kp, the steady-state solutions are reduced to those already derived for a continuous intravenous infusion (eq. (39.35)) ... 

TABLE 7-5. Weight-Based3 Dosing for UFH Administered by Continuous Intravenous Infusion for Venous Thromboembolism... 

Infliximab 5 mg/kg is also an option for severe UC. Cyclosporine 2 to 4 mg/kg per day given as a continuous intravenous infusion should be reserved for patients unresponsive to 7 to 10 days of intravenous corticosteroid therapy. 

IU, international units IV, intravenously SQ, subcutaneously IM, intramuscularly CIV, continuous intravenous infusion. 

CIV, continuous intravenous infusion DFS, disease-free survival. 

The short plasma half-life of dobutamine (1-2 minutes) was found by Murphy et al. (4) to be due to the rapid redistribution of the drug from the plasma to the tissue. However, plasma half-life of radioactivity following the administration of 14C-dobutamine was 1.9 hours. The major circulating metabolite is the glucuronide conjugate of 3-0-methyldobutamine. During a continuous intravenous infusion of dobutamine, the plasma level of the parent drug reach a maximum within 8 to 10 minutes, while those of the metabolites peak be-... 

Thompson, J.A. et al., Prolonged continuous intravenous infusion interleukin-2 and lym-phokine-activated killer-cell therapy for metastatic renal cell carcinoma., J. Clin. Oncol., 10, 960, 1992. 

Bolus intravenous, intramuscular, or subcutaneous injections can be administered by a single person by securing the animal s arm through the cage bars (Mazue and Richez, 1982). For safety considerations, many investigators prefer to have the animal physically restrained by a second person before the injection is given. Arterial injections (via the femoral artery) as well as limited or continuous intravenous infusion (via catheterization of the femoral or jugular vein) are other less commonly used parenteral routes in the monkey. 

Rossignol DP, Wasan KM, Choo E, Yau E, Wong N, Rose 1, Moran 1, Lynn M. (2004) Safety, pharmacokinetics, pharmacodynamics and plasma lipoprotein distribution of eritoran (E5564) during continuous intravenous infusion into healthy volunteers. Antimicrob Agents Chemother 48 3233-3240. 

Working out the rate of a continuous intravenous infusion is another job you may have to do - although in most hospitals there are protocols or other guides that already take account of the kinetics of the drugs used. This is how they were devised in the first place. 

Theoretical depiction of plasma concentrations following either an intravenous bolus dose immediately followed by initiation of a continuous intravenous infusion or initiation of a continuous intravenous infusion only. 

The onset of the hypotensive action of sodium nitroprusside is rapid, within 30 seconds after intravenous administration. If a single dose is given, the action lasts for only a couple of minutes. Therefore, sodium nitroprusside must be administered by continuous intravenous infusion. After the infusion is stopped, blood pressure returns to predrug levels within 2 to 3 minutes. 

Octreotide Sandostatin) is a synthetic somatostatin analogue. It is used in a variety of situations and must be given subcutaneously or intravenously. Most commonly, it is used as a continuous intravenous infusion in patients hospitalized with bleeding varices, because it de-... 

For continuous intravenous infusion studies, the implantation of catheter is performed on gestation day I to allow the recovery from the surgery before the start of treatment on GD6. The animals are maintained on continuous infusion with physiological saline between implantation and the start of treatment. 

During a continuous intravenous infusion of V into a subject at 0.27 mg/kg per minute samples of spinal fluid taken at 60 and 150 min after the start of the infusion contained a mean of 68.3% + 2.4% of the serum concentration of the oxime at the same tlme.H subject given an Infusion of 2-PAM I for 60 min at 0.73 mg/kg per minute had a serum concentration of the oxime of 2,8 mg/100 ml at the end of the infusion, but had no detectable concentration of that oxime in the spinal fluid. These findings corroborate the idea that V may have readier access than the pyridinium oximes to the brain. 

Route of administration ReoPro is administered as an intravenous bolus, followed by a continuous intravenous infusion. 

The duration of action is short and the drug is administered by continuous intravenous infusion at 2-15 pg-kg-l-min-1 depending on the response. 

If the asthma attack is relieved, the clinician might want to maintain this plasma level using oral theophylline, which might be given every 12 hours using an extended-release formulation to approximate a continuous intravenous infusion. According to Table 3-1, Fora is 0.96. When the dosing interval is 12 hours, the size of each maintenance dose would be ... 

Fenoldopam is rapidly metabolized, primarily by conjugation. Its half-life is 10 minutes. The drug is administered by continuous intravenous infusion. Fenoldopam is initiated at a low dosage (0.1 mcg/kg/min), and the dose is then titrated upward every 15 or 20 minutes to a maximum dose of 1.6 mcg/kg/min or until the desired blood pressure reduction is achieved. 

With continuous exposure to nitrates, isolated smooth muscle may develop complete tolerance (tachyphylaxis), and the intact human becomes progressively more tolerant when long-acting preparations (oral, transdermal) or continuous intravenous infusions are used for more than a few hours without interruption. 

Argatroban is a small molecule thrombin inhibitor that is FDA-approved for use in patients with HIT with or without thrombosis and coronary angioplasty in patients with HIT. It, too, has a short half-life, is given by continuous intravenous infusion, and is monitored by aPTT. Its clearance is not affected by renal disease but is dependent on liver function dose reduction is required in patients with liver disease. Patients on argatroban will demonstrate elevated INRs, rendering the transition to warfarin difficult (ie, the INR will reflect contributions from both warfarin and argatroban). (INR is discussed in detail in the discussion of warfarin administration.) A nomogram is supplied by the manufacturer to assist in this transition. 

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