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Type of information:
experimental study
Adequacy of study:
supporting study
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Documentation insufficient for assessment

Data source

Reference Type:
Absorption of Sulfate from Orally Administered Magnesium Sulfate in Man
Morris ME & Levy G
Bibliographic source:
J Toxicol Clin Toxicol, 20(2):107-114

Materials and methods

Study type:
medical monitoring
Endpoint addressed:
basic toxicokinetics
Test guideline
no guideline available
Principles of method if other than guideline:
The purpose of this investigation was to determine the suitability of orally administered magnesium sulfate as a source of sulfate for counteracting the systemic depletion of sulfate caused by large doses of certain drugs that are metabolised to sulfate conjugates. Seven healthy men received 13.9 g magnesium sulfate USP via oral administration in 4 equal hourly increments.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
Magnesium sulfate USP heptahydrate
Magnesium sulfate USP heptahydrate


Type of population:
Details on study design:
7 healthy men who had not been taking medications for at least 1 week participated in the study. There were no dietary restrictions. Total urine volume was collected for 3 consecutive 24 h periods on 2 occasions, one week apart. The subjects received either 13.9 g magnesium sulfate USP (the heptahydrate salt, equivalent to 6.8 g of the anhydrous salt) in 4 divided portions of 3.48 g in 100 mL water at one hour intervals or they took only the 4 portions of water, in the morning after a light, low-fat breakfast. The urine samples, which were collected at approximately 4 h intervals during the day and over 8 hours at night were frozen immediately after collection pending assay.
Inorganic sulfate was assayed by HPLC.

Results and discussion

The absolute baseline excretion rate of inorganic sulfate by the subjects varied from 17.6 to 30.4 mmoles/day.
The urinary excretion of inorganic sulfate after magnesium sulfate administration, corrected for baseline excretion, ranged from only 11.8 to 59.7% of the administered amount of sulfate during the first 24 h. The average was 30.2 ± 17.2% of the dose. Sulfate excretion during the subsequent 24 h periods was negligible after subtraction of baseline values. The excretion rate of creatinine during the first 24 h after magnesium sulfate administration was similar to the individual's average baseline value.
All 7 subjects reported gastrointestinal adverse effects after magnesium sulfate ingestion, ranging from upset stomach to diarrhoea. 6 subjects experienced one or more episodes of loose stools or diarrhoea.

Any other information on results incl. tables

Table 1. Urinary Excretion of Inorganic Sulfate byMen after Oral Administration of 13.9 g (56.6 mmoles) Magnesium Sulfates U.S.P.


Mean ± SD, n=7


Age (yr)

28.7 ± 6.3


Body weight (kg)

75.8 ± 6.0


Baseline excretion rate of inorganic sulphate






(mmoles/ 70 kg/ day)



Baseline excretion rate ratio, sulfate/creatininea



Cumulative excretion of administered excretion of administered sulfate (% of dose)



In 24 hr



In 48 hr



In 72 hr




a The excretion rate of creatinine (mean ± SD) was 14.7 ± 1.8 mmoles/70 kg/day. The Vaseline excretion rates of creatinine and inorganic sulfate for each subject are the mean of results obtained on 3 consecutive days.

b Results in parentheses were obtained by using the baseline excretion ratio, sulfate/creatinine, to correct for excretion of endogenous inorganic sulfate.

Applicant's summary and conclusion

Oral administration resulted in the urinary excretion of an amount of inorganic sulfate equivalent to 30.2 ± 17.2 % of the dose during the first 24 h. Excretion during the subsequent 48 h was negligible. 6 of the subjects experienced loose stools or diarrhoea. Compared to sodium sulfate, magnesium sulfate appears to be absorbed less completely and more erratically and to produce more adverse effects.
Executive summary:

This study summary was provided for the registration of calcium sulfate.