At what magnesium level does loss of patellar reflex occur?

The loss of patellar reflex typically occurs at a magnesium level ranging from 8 to 12 mg/dL. Magnesium plays a crucial role in neuromuscular transmission, and elevated serum magnesium levels can lead to various physiological effects, including muscle relaxation and decreased neuromuscular excitability.

In particular, when serum magnesium levels rise to this range, the neuromuscular junctions become less responsive, which can result in diminished or absent reflexes, including the patellar reflex. This phenomenon is especially important to monitor in clinical settings, such as during the management of conditions like preeclampsia or eclampsia, where magnesium sulfate may be administered for seizure prophylaxis. Recognizing the levels at which reflexes begin to diminish helps in assessing potential toxicity and guiding treatment appropriately.

Understanding these levels aids in safe management in obstetric care, particularly when considering the therapeutic use of magnesium sulfate in pregnant patients.