Lithium concentrations

Sa.Ia.rs and Lakes. Brines having high lithium concentration are found in salars of northern Chile, southwestern Bohvia, and northwestern Argentina. Brines of lower lithium concentration are found in salars in the western United States and the Tibetan Plateau. Brines pumped from beneath the surface of the Salar de Atacama (Chile) and Silver Peak (Clayton Valley, Nevada) are used for commercial production of lithium uti1i2ing solar evaporation (see Chemicals frombrines). The concentration of selected ions in brines from salars and lakes of potential commercial interest worldwide are shown in Table 1. 

Economic Aspects and Uses. In 1976, one-third of the lithium produced in the United States was extracted from brines of Seades Lake and Silver Peak (44,45). Since then, lithium production at Seades Lake has been discontinued and the lithium concentration at Silver Peak is decreasing. During the 1980s lithium extraction was started at the Salar de Atacama, Chile. This is the largest lithium production plant in the wodd using brine as its raw material. 

However, the reaction rate of LiA.Cn depends on the lithium concentration at the surface of the carbon particles, which is limited by the rather slow transport kinetics of lithium from the bulk to the surface LI7-19, 39]. As the melting point of metallic lithium is low (-180 °C) there is some risk of melting of lithium under abuse conditions such as short-circuiting, followed by a sudden breakdown of the SEI and a violent reaction of liquid lithium... 

Following initial assessment, including evaluation of potential suicidality, support systems, and need for inpatient versus outpatient treatment, MW was hospitalized briefly, then followed in the community on medication along with psychotherapy. She has abstained from illicit substances and has returned to her job. She has responded well to treatment with sustained-release lithium carbonate 900 mg once daily at bedtime with a snack. Steady-state 12-hour serum lithium concentrations have stabilized at 0.9 mEq/L (0.9 mmol/L). She now returns to clinic for routine followup. She has tolerated the lithium except for a mild tremor and a gain of 7 pounds (3.2 kg). She is willing to accept these side effects for now, but asks about how long she must take medication since she is now feeling well. 

Lithium presents yet another model of ethnic variation in side effects and response. It is well established that African Americans show a higher red blood cell (RBC) to plasma ratio of lithium concentration when compared to Asians and... 

Initially, serum lithium concentrations are checked once or twice weekly. After a desired serum concentration is achieved, levels should be drawn in 2 weeks, and if stable, they can be drawn every 3 to 6 months. 

Lithium, while not required for life, is used therapeutically in the form of lithium carbonate for the treatment of manic depression although its mechanism of action remains a mystery. Effective treatment requires attaining serum lithium concentrations of between 0.8 and 1.2 mmol/L. 

Re (ii). The "salt effect" is more intriguing. At low lithium concentrations (lithium is the most effective cation) the reaction is first order in the salt concentration and zero order in rhodium, methyl iodide, and carbon monoxide. The rate steeply increases with the lithium concentrations. At high lithium concentrations the rate dependencies equal the Monsanto process, i.e. first order in rhodium and methyl iodide, and zero order in CO. The metal salts are involved in two reactions ... 

For Co, the energy of /JS-(Li jCo)tet(LijX2o3)oct08 by contrast never drops below that of l-l iJZoOz- The results of Figure 8 for crystalline structures, like those in Table 1, mimic the results of the tetrahedral defect calculations (Figure 4). In each case tetrahedral Co is found to be unfavorable at all lithium concentrations and oxidation states considered, while tetrahedral Mn is found to be favorable at the Lii/2Mn02 composition when it has a -1-2 valence. 

Like V, Cr is calculated to maintain a +3.5 oxidation state in both octahedral and tetrahedral coordination at Xu = 1/2 (Table 2). At this lithium concentration the projected change in LFSE and SPE is higher for Cr than for V, which is consistent with the greater value of AEoct—tet calculated for Cr in Table 2. This supports Cr having a stronger preference for octahedral sites at the +3.5 valence than V. At +4 valence Cr was calculated to have the lowest AEoct—tet in Table 3. This is consistent with the relatively low projected change in LFSE and SPE for Cr + moving from octahedral to tetrahedral coordination ((4/5)Ao - (6/5)At). 

Add lithium to a standard antidepressant (e.g. an SSRI) maintaining the plasma lithium concentration at 0.4-0.6mmol/l. This is a well-established method with approximately 50% of the patients responding. However, the plasma lithium concentration must be monitored. 

Lithium is a drug with a narrow therapeutic index and therefore plasma concentrations are regularly monitored. Lithium is used in the prophylaxis and treatment of mania. Concurrent administration of lithium and diuretics, particularly the thiazides, is contraindicated as lithium excretion is reduced, resulting in increased plasma-lithium concentration and hence toxicity. 

Lithium is used in the prophylaxis and treatment of mania and in the prophylaxis of bipolar disorders and recurrent depression. Lithium should be stopped 24 hours before major surgery but the normal dose can be continued for minor surgery, with careful monitoring of fluids and electrolytes. After major surgery, renal function is reduced and this may compromise clearance of lithium. Lithium is a drug with a narrow therapeutic index and it should be avoided if possible in patients with renal impairment. Renal function should be tested before initiating treatment. If lithium is given to patients with renal impairment, a reduced dose should be used and serum lithium concentrations should be monitored closely. 

The fifth product was detected at high lithium concentrations. Its IR spectrum presented a N=N stretching mode at 1795 cm , characteristic of the Li+ N2 ion pair with side-on bonding of the lithium atom and equivalent nitrogen atoms. However, this species was not observed in solid argon without ethylene having been added to the sample . 

The fluorescence of compounds such as 29 significantiy increases in the presence of lithium perchlorate. The increase is proportional to the lithium concentration. In MeCN the linear range is 2 to 100 [xM of LiC104, while in MeOH the concentration has to be >30 mM. ... 

Serum lithium levels Draw blood samples immediately prior to the next dose (8 to 12 hours after the previous dose) when lithium concentrations are relatively stable. Do not rely on serum levels alone. 

Indications and Dosages Alert During acute phase, a therapeutic serum lithium concentration of 1-1.4 mEq/L is required. For long-term control, the desired level is 0.5-1.3 mEq/L. Monitor serum drug concentration and clinical response to determine proper dosage. 

Serum lithium concentrations drawn immediately prior to next dose (8-12 hr after previous dose), monitor biweekly until stable then q2-3mo therapeutic range 1.0-1.5 mEq/L (acute), 0.6-1.2 mEq/L (maintenance)... 

A 17-year-old boy with bipolar disorder is started on lithium therapy at 600 mg bid. The initial lithium concentration is 0.8 mmol/L. As the patient s pressured speech and labile mood do not improve with time, the psychiatrist in charge wonders whether the lack of efficacy is due to insufficient coverage or to noncompliance. A repeat trough level is 0.3 mmol/L (Fig. 4.4A). 

FIGURE 4.4 A Lithium plasma concentration time profile based on a population pharmacokinetics model (Taright et al., 1994). Closed circles are the actual measured lithium concentrations broken lines represent the therapeutic range (0.6-1.2 mmol/L). B Individualized lithium plasma concentration time profile based on the population model with feedback of measured concentrations (Bayesian recalculation). Closed circles are the measured lithium concentrations. The second part of the curve is the predicted lithium concentration profile after increasing the dose to 1000 mg lithium carbonate twice daily, based on a target of 0.6-1.2 mmol/L (broken lines). 

Reversible electrocardiographic (EKG) T-wave depression occurs frequently with therapeutic serum lithium concentrations. Arrhythmias have occurred rarely. The cardiac effects of lithium may result partly from displacement of potassium from intracellular myocardial sites by lithium, resulting in a slow, partial depletion of intracellular potassium (Kawata, 1979). 

Another approach has been the study of RBC/plasma lithium concentration, which is an expression of the relationship between intracellular and extracellular levels. 

At one time, sustained-release preparations were thought to reduce renal toxicity, but more recent evidence has cast doubt on this assumption ( 313). A patient on long-term maintenance lithium should have renal function monitored periodically (i.e., every 12 months) with a urinalysis, BUN, and creatinine. If abnormal, a more intensive evaluation should include 24-hour urine osmolality and creatinine clearance. It is advisable to reduce maintenance lithium to optimal minimal dose-blood levels and, if possible, to avoid concomitant antipsychotics, which may enhance toxicity. Some data support the use of a once-a-day dose schedule to minimize peak lithium concentrations over a 24-hour period (314). 

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