Pharmacological Management of Preeclampsia:

Magnesium SulfatePRESENTED BY:

LAURA NUNEZ, BSN, RN

Magnesium Sulfate in ObstetricsThere are multiple conditions treated in the obstetrical setting with magnesium sulfate including:• Pre-term onset of labor• Pregnancy induced

hypertensive disorders• Management and

prophylaxis of seizures. (Nicholas, 2016).

Preeclampsia: Pathophysiology• in peripheral vascular

resistance due to sensitivity to the vasoconstrictor angiotensin II and in vasodilators.

• Vasospasm occurs = BP• Endothelial dysfunction,

systemic inflammatory response, and increased capillary permeability occur triggering decreased circulation to the kidneys, liver, brain, and placenta.

(Nettina, 2014).

Some unknown cause

Arteriolar vasospasms and vasoconstriction

Vascular endothelial

damage

Leakage of plasma in EVS +

platelet aggregation

colloidal osmotic pressure

Potential for hypovolemia,

pulmonary edema

Alteration in tissue perfusion/

oxygenation to vital organs

Liver- ischemia/necrosis/e

dema

Kidneys- decreased

GFR/oliguria/proteinuria

Brain- cerebral edema/

hemorrhage/seizures

Mechanism of ActionANTICONVULSANT• inhibits the N-methyl-D-aspartate

(NMDA) receptors, limiting the effect of excitotoxic neurotransmitters such as glutamate and increasing the seizure threshold.

acute hypertensive event • disruptions in the blood-brain barrier

(BBB) allow passage of MgSO4 to the brain parenchyma enabling the drug to act as an anticonvulsant

(Euser & Cipolla, 2009)

ANTIHYPERTENSIVE• exact mechanism of action is unknown

• ↓ vasospasm induced by vasoconstrictor substances, such as endothelin-1, in vascular beds thus improving hypertension (Korish, 2012).

calcium antagonist properties• block calcium from entering into vascular

smooth muscle ↓ intracellular calcium activity

• inactivation of calmodulin-dependent myosin light chain kinase activity and ↓ contraction = arterial relaxation and ↓ arterial blood pressure

(Euser & Cipolla, 2009; Zhou, et al., 2013)

Potential InteractionsIncreased CNS depressant effects:• Barbiturates, hypnotics, narcotics, or systemic anestheticsIncreased hypotensive effects:• Calcium channel blockersDecreases absorption of:• Tetracycline's, quinolones, and thyroid medicationsChanges in cardiac conduction causing heart block:• If calcium is used to treat magnesium toxicity in digitalized patients

(L. Homburg, personal communication, February 6, 2017; Vallerand & Sanoski, 2017 ).

Adverse Drug ReactionsTypically result of magnesium toxicity

• Loss of patellar reflexes• Respiratory paralysis• Heart block• Collapse of circulatory system• Death

(L. Homburg, personal communication, February 6, 2017 ; Medscape, 2017)

Side EffectsVasodilatory effects:• Feeling of warmth• Lethargy• Facial flushing• hypotensionOther side effects:• Sweating• Diminished reflexes• Confusion• Intense thirst

(Smith, et al., 2013; Vallerand & Sanoski, 2017).

PharmacokineticsIV absorption

• Complete bioavailabilty• Onset= immediate• Peak= unknown• Duration = 30 minutes

Distribution

• widely distributed• 25-30% protein binding (albumin)• 1-2% total magnesium located in

extracellular fluid space• Primarily in serum and RBCs• Crosses into placenta

(L. Homburg, personal communication, February 6, 2017; Epocrates Inc., 2017).

Metabolism• Not metabolizedExcretion• Primarily by kidneysHalf-life• Unknown

Drug Binding IssuesClassification of drugs that affect binding of MgSO4

• Diuretics• Cyclosporines• Aminoglycosides

Results• Induce renal excretion of magnesium• Potential binding issues• Reduced effectiveness of the drug

(L. Homburg, personal communication, February 6, 2017).

Improving Communication• Access to resources for drug

information → assist providers in ensuring MgSO4 is appropriately prescribed for the patient’s condition

• Thorough documentation of treatment plan → improve communication between members of the interdisciplinary team

• Additional co-signer for administration → reduce errors in medication administration

• Required documentation flowsheet for monitoring → help identify early signs and symptoms of toxicity in patients receiving MgSO4

(L. Homburg, personal communication, February 6, 2017)

Application to PracticeClinical setting• Enhancing knowledge and

understanding of benefits and serious risks for both mother and neonate.

• Improving patient safety by reducing medication administration errors, and early identification of MgSO4 toxicity

Education setting• Enhance student knowledge of

pharmacologic principles related to MgSO4 to assist in improving patient safety measures when they join the nursing workforce

References• Epocrates Inc. (2017). magnesium sulfate. Retrieved from Epocrates:

https://online.epocrates.com/drugs/10710/magnesium-sulfate/Monograph• Euser, A. G., & Cipolla, M. J. (2009). Magnesium sulfate treatment for the prevention of eclampsia: A brief review.

Stroke, 40(4), 1169-1175. doi: 10.1161/STROKEAHA.108.527788.• Korish, A. A. (2012). Magnesium sulfate therapy of preeclampsia: an old tool with new mechanism of action and

prospect in management and prophylaxis. Hypertension Research, 35(1), 1005-1011. doi:10.1038/hr.2012.103.• Medscape. (2017). Magnesium sulfate. Retrieved from Medscape: http://reference.medscape.com/drug/mgso4-

magnesium-sulfate-344444• Nettina, S. M. (Ed.). (2014). Complications of the childbearing experience (10th ed.). Ambler, PA: Wolters Kluwer

Health | Lippincott Williams & Wilkins.• Nicholas, J. (2016). Drugs associated with pregnancy, labor and delivery, and lactation. In B. T. Smith (Ed.),

Pharmacology for Nurses (pp. 327-342). Burlington, MA: Jones & Bartlett Learning.• Smith , J. M., Lowe, R. F., Fullerton, J., Currie, S. M., Harris, L., & Felker-Kantor, E. (2013). An integrative review of the

side effects related to the use of magnesium sulfate for preeclampsia and eclampsia management. BMC Pregnancy & Childbirth, 13(1), 1-11. doi:10.1186/1471-2393-13-34.

• Vallerand, A. H., & Sanoski, C. A. (2017). Magnesium sulfate. In Davis's Drug Guide for Nurses (15th ed.). Philadelphia, PA: F.A. Davis Company.

• Zhou, Q., Shen, J., Zhou, G., Shen, L., Zhou, S., & Li, X. (2013). Effects of magnesium sulfate on heart rate, blood pressure variability and baroreflex sensitivity in preeclamptic rats treated with L-NAME. Hypertension In Pregnancy, 32(4), 422-431. doi:10.3109/10641955.2013.824978.