Calcium magnesium dihydroxide oxide

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 when administered as magnesium chloride (28Mg) and citrate (stable isotopes), constituting well soluble salts from which magnesium can be assumed to be well bioavailable. The data are used for read-across from supporting substances for evaluating oral absorption.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Intestinal absorption of magnesium in man

Author:

Roth, P.; Werner, E.

Year:

1979

Bibliographic source:

Int. J. App. Rad. Isotop. 30, 523-526

Materials and methods

Study type:

study with volunteers

Endpoint addressed:

basic toxicokinetics

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Toxicokinetics, oral absorption (human)

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Magnesium chloride

EC Number:

232-094-6

EC Name:

Magnesium chloride

Cas Number:

7786-30-3

IUPAC Name:

magnesium dichloride

Constituent 2

Reference substance name:

Citric acid, magnesium salt

EC Number:

231-923-9

EC Name:

Citric acid, magnesium salt

Cas Number:

7779-25-1

IUPAC Name:

magnesium 2-(carboxymethyl)-2-hydroxysuccinate

Constituent 3

Reference substance name:

Magnesium citrate

IUPAC Name:

Magnesium citrate

Details on test material:

- Name of test material (as cited in study report):
1) 28Mg magnesium chloride
2) Magnesium citrate
No further details are given.

Method

Type of population:

general

Subjects:

- Number of subjects exposed: 23
- Sex: 12 males and 11 females
- Age: 24-46 years (men) and 23-43 years (women)
- Known diseases: none
No further details are given.

Ethical approval:

not specified

Remarks:

The subjects are characterised as "volunteers" in the publication.

Route of exposure:

oral

other: intravenous

Reason of exposure:

intentional

Exposure assessment:

not specified

Details on exposure:

Fractional intestinal absorption of magnesium was measured by means of a whole-body counter in healthy volunteers. After an overnight fast 2-4 µCi of 28Mg (as Mg chloride) were given orally in 100 ml of deionised water.
Different amounts of stable Mg (as Mg citrate) were added to the oral test dose of 28Mg. There were 5 groups corresponding to total magnesium intakes of 0.3, 1.3, 4.2, 12.5 and 41.7 mmol, respectively. The 28Mg activity retained 5 days after the oral administration was measured with WBC. To correct for the excretion of absorbed activity within this period, a tracer dose of 28Mg was given intravenously (4 µCi 28Mg).

Examinations:

The natural body radioactivity was counted before oral administration with the whole-body counter (WBC).
Five days after injection the retention of 28Mg was measured again with the WBC and fractional intestinal Mg absorption was calculated.

Medical treatment:

no medication

Results and discussion

Clinical signs:

no data

Results of examinations:

At the lowest Mg intake (0.3 mmol), fractional absorption averaged at 0.7 ± 0.11. At intakes of 1.3, 4.2, and 12.5 mmol, the corresponding values are 0.48 ± 0.09, 0.29 ± 0.05 and 0.2 ± 0.05, respectively. At the highest load studied (41.7 mmol), 0.14 ± 0.05 of the oral dose were absorbed. The absorption curve (amount absorbed vs oral intake) shows a biphasic pattern and can be broken down into a linear and a saturable component (see attached figure). Approximately 10 % of oral Mg is absorbed by the linear process, which probably reflects passive diffusion. The maximum transport capacity of the saturable process was estimated at 1.1 mmol and the half saturation load at 2.5 mmol. The saturable component probably reflects a process of facilitated diffusion, but not active transport.

Effectivity of medical treatment:

No medication received (not applicable).

Outcome of incidence:

Not applicable

Applicant's summary and conclusion

Conclusions:

This study suggests that, when administered as a soluble salt at doses in the physiological range (approximately 10 mmol), fractional intestinal magnesium absorption is 20 %. Absorption increases at lower doses (70 % at 0.3 mmol) and decreases at higher doses (14 % at 41.7 mmol).