| Calcium algorithm | Intractable problems |
| PTH, alfacalcidol and calcitriol | Calcium after parathyroidectomy |
| Aluminium | Further information |
| Phosphate algorithm | Patient information |
Aims of management are maintenance of healthy skeletal architecture, through achieving normocalcaemia and limited hyperphosphataemia, and by controlling PTH. Monitoring frequencies etc are biased towards dialysis patients. Less often in pre-dialysis patients and transplant recipients.
Total calcium should be measured every 4-12 weeks and is often approximately corrected by adding 0.02mmol/l for every g/l the serum albumin is below 40g/l. This adjusted calcium can then be sued, along with the iPTH taken every six months, to determine tratment according to the calcium algorithm below:
iPTH should be measured initially when GFR drops below 40-50mls/min. At this stage diet should be reviewed for both phosphate and protein content. High PTH levels should lead to introduction of alfacalcidol or calcitriol therapy, Calcium levels permitting. The standard starting dose is 0.25 micrograms (250 nanograms) daily. High iPTH results (eg > 500ng/l) may justify larger doses of calcitriol.
Note that the target range is higher than (2-4x) the normal range, in order to prevent adynamic bone disease resulting from overtreatment.
Alfacalcidol and Calcitriol are equally effective and equipotent. Both should be used at doses of 0.25, 0.5 or 1.0 micrograms for daily oral therapy. If the patient goes outwith the protocol limits, they should be taken out of the protocol and treated separately.
Aluminium should be measured every three months in patients on Al(OH)3. A result of greater than 2.2 micromol/l indicates a high risk of aluminium poisoning and rquires cessation of Al (OH3). Levels over 1 should lead to review of therapy.
Serum phosphate (Pi, PO4) should be measured every 4-12 weeks to adjust therapy with phosphate binders. This can be done using the phosphate algorithm below:
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PHOSPHATE BINDERS For inpatients, prescribe at 8, 12 and 6 and write "with food". Very approximately, one tablet of each is equivalent (larger dose size for sevelamer): Calcium acetate (CaAc) is the first-line binder for all patients unless they are hypercalcaemic. It is effective but delivers a significant calcium load. Hypercalcaemia may occur, and in the long term the calcium load may accelerate vascular and extravascular calcification. Maximum dose is 6 tablets daily but this may be too much for long term therapy. Calcium carbonate (CaCO3) is a probably less effective alternative and contains more calcium, but may be useful if patients dislike the calcium acetate formulation. Aluminium hydroxide (e.g. Alucaps) is an effective binder that is relatively palatable. However it is not suitable for long-term use because of concerns about aluminium accumulation and toxicity in renal failure. Monitor Al levels during therapy and be cautious about duration. Sevelamer (Renagel) is an expensive binder that does not cause calcium loading or other known serious long-term toxicity. Used alone It is probably less effective at lowering phosphate and its track record is still relatively short. It is indicated when:
Other agents are in development but have not yet found a fixed place in our local practice. See also 'intractable problems' below. |
Phosphate binder type/ dose is decided using measurements of corrected calcium and phosphate (and see above):
Ca >2.6: follow the algorithm above for management of alfacalcidol/calcitriol therapy, and consider changing the alfacalcidol or calcitriol dose. Otherwise/also:
- If on CaAcetate, consider change to Al(OH)3
- If on non-calcium binders, discuss - review PTH level, other cause
- If intractable and on dialysis, consider lowering dialysate calcium
Ca 2.16 - 2.6
- If on Al(OH)3 change (back) to Ca Acetate (if other factors corrected).
Ca <2.16: follow algorithm above for management of alfacalcidol/ calcitriol therapy. Otherwise/also:
- If already on Ca Acetate and PO4 over 1.5, increase CaAc dose
- If Pi below 1.5, give CaAc between meals as a supplement
Patients with substantial hyperparathyroidism may develop severe hypocalcaemia immediately after parathyroidectomy. This is most likely if bone disease is obvious and severe, in which case it may be minimised by pre-administration of alfacalcidol or calcitriol (see third point below).
UK CKD guidelines - short eCKD guide on management of calcium and phosphate in Stage 3 CKD (suggests PTH and vitamin D management in primary care, which goes beyond our local guidance)
Lothian Joint Formulary shared care protocols for prescribing in primary care include sevelamer. LJF home page
The EdRenINFO pages on chronic renal failure and on diet touch on these issues.
Paddy Gibson and Peter Kyriakoudis were the original authors for this page (2001). Revised December 2003 (ANT/RJW) and last updated (ANT)
NOTE that the accuracy of any statements in this information CANNOT be guaranteed. It is published in the belief that it is correct, and we endeavour to keep it so - but we do make mistakes. Furthermore, over some subjects there are differing opinions, or differing degrees of certainty. We have usually not attempted to discuss these here because the aim has been to provide an immediate and brief guide. In all areas, prior medical knowledge is assumed. The EdRenHANDBOOK is not suitable for use by those without such a background. Contact us by email or at the address given at the foot of the contents page with any comments or corrections.