Dolomite (CaMg(CO3)2), calcined

Direct observations: clinical cases, poisoning incidents and other

Administrative data

Endpoint:

direct observations: clinical cases, poisoning incidents and other

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Reasonably well-documented publication. In this study, intestinal absorption of magnesium was studied in human volunteers receiving magnesium controlled diet, from which magnesium can be assumed to be well bioavailable. The data are used for read-across from a supporting substance for evaluating oral absorption.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Magnesium absorption and metabolism in patients with chronic renal failure and in patients with normal renal function

Author:

Spencer, H. et al.

Year:

1980

Bibliographic source:

Gastroenterology 79, 26-34

Materials and methods

Study type:

study with volunteers

Endpoint addressed:

basic toxicokinetics

Test guideline

Qualifier:

according to guideline

Guideline:

other: DHEW (Department of Health, Education, & Welfare) guidelines

Principles of method if other than guideline:

Toxicokinetics in humans
Oral bioavailability of dietary magnesium

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Magnesium

EC Number:

231-104-6

EC Name:

Magnesium

Cas Number:

7439-95-4

IUPAC Name:

magnesium

Details on test material:

- Name of test material (as cited in study report): Magnesium
- Source: Dietary, i.e. from natural sources, strictly controlled
No further details are given.

Method

Type of population:

general

Subjects:

- Number of subjects exposed: 8
- Sex: male
- Age: 47-67 years
- Known diseases: Chronic renal failure; subjects were in good physical condition and had normal gastrointestinal and liver function
- Other: The serum levels of creatinine were elevated, ranging from 2.4 to 14.6 mg/100 ml, as were the levels of blood urea nitrogen (BUN), which ranged from 26 to 106 mg/100 ml. The creatinine clearance ranged from 5 to 54 ml/minute.
- Control subjects (normal renal function): 10 age matched patients
No further details are given.

Ethical approval:

confirmed and informed consent free of coercion received

Remarks:

In compliance with DHEW guidelines (United States Department of Health, Education, and Welfare).

Route of exposure:

oral

Reason of exposure:

intentional

Exposure assessment:

measured

Details on exposure:

Sixteen Mg balance studies were carried out under strictly controlled dietary conditions in the Metabolic Research Ward. 10 of these studies were carried out during a low Mg intake averaging 159 mg/day and a low Ca intake averaging 200 mg/day, and 6 were carried out during similar dietary Mg intake but during different Ca intakes ranging from 800-2000 mg/day. 33 control studies were carried out.
The duration of the studies of the patients with chronic renal failure averaged 28 days during the low Ca intake and 72 days during the higher Ca intakes. Patients received diets containing 172 mg Mg.

Examinations:

Urine and stool specimens were collected. The body weight, 24-hour urine volume, and urinary excretion of creatinine were determined daily. Metabolic balances of Mg were determined in each 6-day study period on aliquots of the diet and on aliquots of 6-day collection pools of urine and stool. Mg and Ca in the diet, urine, stool and serum were determined by atomic absorption spectroscopy.

Medical treatment:

no medication

Results and discussion

Clinical signs:

no data

Results of examinations:

The average net absorption of Mg of patients with chronic renal failure was significantly lower (17 % of magnesium intake) than the absorption of patients with normal renal function (48.5 %). The lower absorption of Mg of patients with chronic renal failure was due to the significantly higher faecal Mg excretion, averaging 82.5 % of the Mg intake, compared with an average of 51.5 % for patients with normal renal function.
The faecal/urinary Mg excretion ratio for patients with normal renal function was close to 1.0, whereas it averaged 1.75 for patients with chronic renal failure, which indicates a shift of the Mg excretion from the kidney to the intestine.
The Mg balance did not differ significantly from that of age-matched patients with normal kidney function receiving similar or higher Mg intake. In a long-term study of a patient with chronic renal failure, the net absorption of Mg was greater during a higher Mg intake than during the lower Mg intake. The Mg absorption was only half the value, 24 % vs 48 %, for patients with normal renal function receiving the same Mg intake. Increasing the Ca intake from 200 to 800, 1400, and 2000 mg/day did not change the Mg balance or the net absorption of Mg of patients with chronic renal failure and of patients with normal renal function.

Effectivity of medical treatment:

Not applicable - no medication received.

Outcome of incidence:

no data

Applicant's summary and conclusion

Conclusions:

In healthy subjects, absorption of magnesium from the diet was found to be approximately 50 %.