Intravenous Magnesium Sulfate Rapidly Alleviates Headaches of Various Types

BACKGROUND Circumstantial evidence points to the possible role of magnesium deficiency in the pathogenesis of headaches and has raised questions about the clinical utility of magnesium as a therapeutic regimen in some headaches. METHODS We evaluated the efficacy of intravenous infusion of 1 gram of magnesium sulfate (MgSO4) for the treatment of patients with headaches and attempted to correlate clinical responses to the basal serum ionized magnesium (IMg2+) level. We also determined if patients with certain headache types exhibit low serum IMg2+ as opposed to total serum magnesium. Using a case-control comparison at an outpatient headache clinic, a consecutive sample of patients presenting with a moderate or severe headache of any type were included in the study. Of the 40 patients in the study (mean age 38.2 +/- 9.4 years; range 14 to 55; 11 men [39.2 +/- 7.3 years] and 29 women [37.8 +/- 10.2 years]), 16 patients had migraines without aura, 9 patients had cluster headaches, 4 patients had chronic tension-type headaches, and 11 had chronic migrainous headaches. Total serum magnesium was measured with atomic absorption spectroscopy and a Kodak Ektachem DT-60. Sensitive ion selective electrodes were utilized to measure serum IMg2+ and ionized calcium (ICa2+); ICa2+/IMg2+ ratios were calculated. RESULTS Complete elimination of pain was observed in 80% of the patients within 15 minutes of infusion of MgSO4. No recurrence or worsening of pain was observed within 24 hours in 56% of the patients. Patients treated with MgSO4 observed complete elimination of migraine-associated symptoms such as photophobia and phonophobia as well as nausea. Correlation was noted between immediate and 24-hour responses with the serum IMg2+ levels. Immediate pain relief was observed in 32 (80%) of 40 patients (P < 0.001). In 18. of the 32 patients, pain relief persisted for at least 24 hours (P < 0.005). Of these 18 patients, 16 (89%) had a low serum IMg2+ level. Total magnesium levels in contrast in all subjects were within normal range (0.70-0.99 mmol/L). No side effects were observed, except for a brief flushed feeling. Of the 8 patients with no relief, only 37.5% had a low IMg2+ level. Patients demonstrating no return of headache or associated symptoms within 24 hours of intravenous MgSO4 exhibited the lowest initial basal levels of IMg2+. Non-responders exhibited significantly elevated total magnesium levels compared to responders. Although most subcategories of headache types investigated (ie, migraine, cluster, chronic migrainous) exhibited low serum IMg2+ during headache and prior to intravenous MgSO4, the patients with cluster headaches exhibited the lowest basal levels of IMg2+ (P < 0.01). All headache subjects except for the chronic tension group exhibited rather high serum ICa2+/IMg2+ ratios (P < 0.01, compared to controls). CONCLUSIONS Intravenous infusion of 1 gram of MgSO4 results in rapid relief of headache pain in patients with low serum IMg2+ levels. Measurement of serum IMg2+ levels may have a practical application in many types of headache patients. Low serum and brain tissue ionized magnesium levels may precipitate headache symptoms in susceptible patients.