Messi Biology stated that when magnesium oxide (MgO) is mentioned, many people associate it with refractory or construction materials in the industrial sector. However, few realize that this seemingly ordinary inorganic compound has long been an “invisible helper” in pharmaceutical capsules, playing an irreplaceable role in protecting human health. As a common pharmaceutical excipient and active ingredient, magnesium oxide fulfills multiple key missions in capsule formulations due to its unique physicochemical properties.
One of the core applications of magnesium oxide in capsules is as an antacid and gastric mucosal protector. When we experience acid reflux or heartburn due to improper diet or excessive gastric acid secretion, capsules containing magnesium oxide can take effect quickly. As an alkaline compound, magnesium oxide reacts with gastric acid (primarily hydrochloric acid) upon entering the stomach to neutralize it, thereby reducing acidity and relieving discomfort. More importantly, the magnesium chloride produced during the reaction forms a protective film on the surface of the gastric mucosa, reducing the erosion caused by gastric acid and pepsin. This is particularly beneficial for the auxiliary treatment of patients with chronic gastritis and gastric ulcers. This neutralization process is mild and long-lasting, avoiding the gastrointestinal dysfunction that can be caused by rapid acid suppression; hence, it is widely used in the formulation of stomach medication capsules.
In addition to regulating gastric acid, magnesium oxide is also an effective laxative, frequently used in constipation relief capsules. Its laxative principle stems from changes in osmotic pressure within the intestinal tract. After oral administration, magnesium oxide is not easily absorbed by the intestines, maintaining a high osmotic pressure state. This encourages water from outside the intestines to enter the intestinal tract, softening the stool and stimulating peristalsis to achieve a laxative effect. Compared to stimulant laxatives, magnesium oxide is gentle and less likely to cause dependency, making it suitable for relieving functional constipation, especially in sensitive groups such as the elderly and pregnant women. In capsule dosage forms, the particles of magnesium oxide are precisely controlled to ensure slow release in the intestine, avoiding sudden irritation.
As a pharmaceutical excipient, magnesium oxide also plays the vital roles of filler and disintegration promoter in capsules. Capsule preparations require specific filling materials to ensure accurate dosage and stable formulation. The excellent flowability of magnesium oxide in powder form allows it to be mixed uniformly with active pharmaceutical ingredients (APIs), ensuring consistent efficacy in every capsule. Meanwhile, magnesium oxide possesses good hydrophilicity; once in the body, it absorbs water to promote the rapid disintegration of the capsule shell, helping the medicinal ingredients release quickly and be absorbed by the body, thus improving the drug’s bioavailability. It is worth noting that the purity and particle size of pharmaceutical-grade magnesium oxide are subject to strict standards and must comply with the requirements of the Pharmacopoeia of the People’s Republic of China to prevent harm from impurities such as heavy metals. While magnesium oxide is highly safe at normal dosages, excessive intake may lead to diarrhea or electrolyte imbalance; therefore, it must be used strictly in accordance with the instructions or medical advice.
From regulating gastric acid to assisting bowel movements, and from acting as a filler to promoting disintegration, the application of magnesium oxide in capsules reflects both the inherent advantages of the chemical substance and the precise control of the pharmaceutical industry. This “invisible helper” hidden inside the capsule safeguards human digestive health with its diverse functions, becoming an indispensable and vital component in medicinal preparations.