Sparing agent

Carbohydrates. The materials offered for fat replacement are either carbohydrate or protein and protein-like compounds (29). Table 3 fists carbohydrate fat-sparing agents. Another fisting is available (34) which includes materials offered on the European market. New compounds appear at such a rate that it is difficult to keep a current compilation proceedings from an aimual meeting are published (48). 

Agents acting in the proximal tubule are seldom used to treat hypertension. Treatment is usually initiated with a thiazide-type diuretic. Chlorthalidone and indapamide are structurally different from thiazides but are functionally related. If renal function is severely impaired (i.e., serum creatinine above 2.5 mg/dl), a loop diuretic is needed. A potassium-sparing agent may be given with the diuretic to reduce the likelihood of hypokalemia. 

By themselves, potassium-sparing agents are relatively weak antihypertensives. In general, there are four ways to reduce the activity of the RAS. The first way is the use of p-blockers to reduce renin release from the juxtaglomerular (JG). The second way, the direct inhibition of the activity of renin, although being actively investigated has not been successful in the clinical arena thus far. The third way is to inhibit the activity of the... 

Triamterene (Dyrenium) [Diuretic/Potassium-Sparing Agent]... 

Potassium sparing agents amiloride hydrochloride spironolactone... 

Only about 10% of the Na-i- filtered by the glomerulus is reabsorbed by the distal convoluted tubule (DCT) and therefore the capacity of the thiazide group of diuretics to influence the elimination of Na-H in the urine is limited compared to the loop agents. Thiazides can prevent the reabsorption of up to 5% of the total filtered Na+, whereas the equivalent figure for loop diuretics is about 20%. Thiazides can still produce a moderate naturesis and diuresis compared to carbonic anhydrase inhibitors and the K+-sparing agents. Most thiazides are ineffective at low glomerular filtration rates. They also hinder the ability of the kidneys to produce a dilute urine. 

Hyperkalaemia occurs occasionally with K+-sparing agents and can be dangerous. It is most likely to occur in those on concomitant drug therapy, which raises serum K+. It is also more likely in those with a low GFR. 

Trade Name Potassium-Sparing Agent Hydrochlorothiazide... 

Lock SH et al Double-blind, placebo-controlled study of cyclosporin A as a corticosteroid-sparing agent in corticosteroid-dependent asthma. Am J Respir Crit Care Med 1996 153 509. [PMID 8564089]... 

The most serious side effects of diuretics are fluid depletion and electrolyte imbalance.13,88 By the very nature of their action, diuretics decrease extracellular fluid volume as well as produce sodium depletion (hyponatremia) and potassium depletion (hypokalemia). Hypokalemia is a particular problem with the thiazide and loop diuretics, but occurs less frequently when the potassium-sparing agents are used. Hypokalemia and other disturbances in fluid and electrolyte balance can produce serious metabolic and cardiac problems and may even prove fatal in some individuals. Consequently, patients must be monitored closely, and the drug dosage should be maintained at the lowest effective dose. Also, potassium supplements are used in some patients to prevent hypokalemia. 

The combination of triamterene with indomethacin has been reported to cause acute renal failure. This has not been reported with other potassium-sparing agents. 

Lucky, A.W., Leach, A.D., Laskarzewski, P., and Wenck, H. Use of an emollient as a steroid-sparing agent in the treatment of mild to moderate atopic dermatitis in children. Pediatr. Dermatol. 1997 14 321-4. 

Three common side-effects are (a) first-dose hypotension, (b) persistent dry cough and (c) hyperkalaemia. Other side-effects include gastrointestinal effects (nausea, vomiting, dyspepsia, diarrhoea, altered liver function tests, blood disorders, angioedema, rash, loss of sense of smell (more likely if also on potassium-sparing agents or potassium supplements). 

Azathioprine is effective as a steroid sparing agent in maintenance therapy of Crohn s disease. Use of... 

More usually now, megadose pulses (methylprednisolone 1.0 g i.v. daily for 3 days) are used, followed by oral maintenance with prednisolone and/or a steroid-sparing agent (above). 

Drugs that increase the systemic availability of ciclosporin do not always have negative effects, and several ciclosporin-sparing agents have indeed been used for the purpose of improving efficacy while reducing the cost of treatment. However, use of such combinations should be balanced against their potential risks (273). 

---