Nonsteroidal anti-inflammatory drugs with lithium

Which best describes the mechanism of interaction of nonsteroidal anti-inflammatory drugs (NSAlDs) with lithium salts ... 

Lithium toxicity can occur as a result of intentional overdose therefore, care must be taken when administering lithium to potentially suicidal patients with BPAD. Inadvertent lithium toxicity may also occur. For example, diuretics and nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil, Motrin) slow the excretion of lithium and can lead to accidental toxicity. Consequently, the patient should be advised not to take such commonly available medications while treated with lithium. In addition, dehydration resulting from varied causes such as diarrhea, vomiting, and profuse sweating can lead to accidental lithium toxicity. One should advise the patient who takes lithium to be careful to remain well hydrated at all times and to contact his/her physician if any medical condition arises that may cause rapid fluid losses (e.g., stomach virus, high fevers). 

Renal clearance of lithium is reduced about 25% by diuretics (eg, thiazides), and doses may need to be reduced by a similar amount. A similar reduction in lithium clearance has been noted with several of the newer nonsteroidal anti-inflammatory drugs that block synthesis of prostaglandins. This interaction has not been reported for either aspirin or acetaminophen. All neuroleptics tested to date, with the possible exception of clozapine and the newer atypical antipsychotics, may produce more severe extrapyramidal syndromes when combined with lithium. 

Drug interactions with lithium have been reviewed (569-573) another review focused on interactions in the elderly (573). A review of drug interactions with lithium considered both pharmacokinetic interactions [for example diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs)] and pharmacodynamic interactions (for example antipsychotic drugs, SSRIs) and summarized the most important ones in tabular form (569). 

Phelan KM, Mosholder AD, Lu S. Lithium interaction with the cyclooxygenase 2 inhibitors rofecoxib and cele-coxib and other nonsteroidal anti-inflammatory drugs. J Clin Psychiatry 2003 64 1328-34. 

Walker RG. Lithium nephrotoxicity. Kidney Int Suppl 1993 42 S93-S98. LamSS, Kjellstrand C. Emergency treatment of lithium-induced diabetes insipidus with nonsteroidal anti-inflammatory drugs. Ren Eail 1997 19 183-188. 

Interactions. Several types of drug interfere with lithium excretion by the renal tubules, causing the plasma concentration to rise. These include diuretics (thiazides more than loop type), ACE inhibitors and angiotensin-11 antagonists, and nonsteroidal anti-inflammatory analgesics. Theophylline and sodium-containing antacids reduce plasma lithium concentration. The effects can be important because lithium has such a low therapeutic ratio. Diltiazem, verapamil, carbamazepine and pheny-toin may cause neurotoxicity without affecting the plasma lithium. Concomitant use of thioridazine should be avoided as ventricular arrhythmias may result. 

Most of the renal tubular reabsorption ofU occurs in the proximal tubule. Nevertheless, Id retention can be increased by any diuretic that leads to depletion of Na, particularly the thiazides (see Chapter 28). Renal excretion can be increased by administration of osmotic diuretics, aceta-zolamide or aminophylline, and triamterene. Spironolactone does not increase the excretion of LiL Some nonsteroidal anti-inflammatory agents can facilitate renal proximal tubular resorption of Id and thereby increase concentrations in plasma to toxic levels. This interaction appears to be particularly prominent with indomethacin, but also may occur with ibuprofen, naproxen, and COX-2 inhibitors, and possibly less so with sulindac and aspirin. A potential drug interaction can occur with angiotensin-converting enzyme inhibitors, causing lithium retention (see Chapter 29). 

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