Magnesium Hydroxide
**Magnesium hydroxide** is an oral antacid and laxative used in veterinary medicine. * **Small Animals**: Historically used for esophagitis, gastric hyperacidity, and peptic ulcers, though largely replaced by more effective H2-blockers (e.g., famotidine) and proton-pump inhibitors (e.g., omeprazole). It is still occasionally used as an osmotic laxative (Milk of Magnesia). * **Ruminants**: Highly effective as a rumen alkalinizing agent and laxative for the treatment of **rumen overload syndrome** (grain overload, rumen acidosis). Powder formulations are significantly more effective than boluses for this indication. > **Clinical Pearl**: Magnesium-containing antacids often cause diarrhea, whereas aluminum-containing antacids cause constipation. Many commercial products combine both to balance these effects.
Mecanismo: Acts locally in the gastrointestinal tract: * **Antacid**: Neutralizes gastric hydrochloric acid (HCl) → raises gastric pH. Raising pH >4 minimizes pepsin proteolytic activity, reducing gastric mucosal damage. * **Laxative**: Poorly absorbed magnesium ions create an osmotic gradient → draws water into the intestinal lumen → distends the bowel → stimulates peristalsis. * **Rumen Alkalinizer**: Directly neutralizes excess lactic acid produced during grain overload → increases rumen pH and alters rumen microflora activity.
Dosificación por especie
- Rumen overload syndrome · As above for cattle, but use ⅛th-¼th the amount · PO · q6-12h
- Rumen overload syndrome · As above for cattle, but use ⅛th-¼th the amount · PO · q6-12h
- Antacid · 5-15 mL PO once to twice daily · PO · q12-24h · Using Milk of Magnesia
- Rumen overload syndrome (Adults) · Up to 1 gram/kg (MgOH) mixed in 2-3 gallons of warm water and given PO per tube. May repeat (use smaller doses) at 612 hour intervals. If the rumen has been evacuated, do not exceed 225 grams initially. · PO · q6-12h · Dehydration and systemic acidosis must be concomitantly corrected.
- Rumen overload syndrome (Calves) · As above but use ⅛th-¼th the amount · PO · q6-12h
- Adjunctive gastroduodenal ulcer therapy in foals · 15 mL 4 times a day · PO · q6h · Using Aluminum/magnesium hydroxide suspension
- Adjunctive treatment of hypomagnesemia with GI disease and severe hypocalcemia · 5-15 mL/per dog per 24 hours · PO · q24h · Using Milk of Magnesia
Vías de administración
Contraindicaciones
- Renal disease (due to risk of hypermagnesemia)
- Gastric outlet obstruction (for aluminum-containing products)
- Use cautiously in patients on sodium- or potassium-restricted diets (some products contain significant amounts)
Efectos adversos
- Diarrhea or frequent loose stools
- Hypermagnesemia (especially in patients with severe renal insufficiency)
- Constipation (if using combination products with aluminum)
- Hypophosphatemia (with chronic use of aluminum-containing products)
Interacciones farmacológicas
- Quinidine · Increased absorption or pharmacologic effect may occur
- Sodium Polystyrene Sulfonate · May decrease the potassium-lowering effectiveness; may cause metabolic alkalosis in renal failure patients
- Sustained-release medications · May alter absorption by changing GI transit times when used at laxative dosages
- Sympathomimetic agents · Increased absorption or pharmacologic effect may occur
- Fluoroquinolones · Decreased absorption (chelation); separate doses by at least 2 hours
- Tetracyclines · Decreased absorption (chelation); separate doses by at least 2 hours
- Azole Antifungals (Ketoconazole, Itraconazole) · Decreased absorption due to increased gastric pH; separate doses by at least 2 hours
- Digoxin · Decreased absorption; separate doses by at least 2 hours
- Iron Salts · Decreased absorption; separate doses by at least 2 hours
- H-2 Antagonists · Decreased absorption; separate doses by at least 2 hours
- Thyroid Hormones · Decreased absorption; separate doses by at least 2 hours
- Corticosteroids · Decreased absorption; separate doses by at least 2 hours
Monitoreo
- Electrolyte imbalances (Magnesium, Phosphorus, Calcium) with chronic or high-dose therapy
- Renal function
- Fecal consistency
Sobredosis
Chronic or acute overdose can lead to significant GI upset (severe diarrhea) and electrolyte imbalances (hypermagnesemia, especially in renal failure). Treat symptomatically with fluid therapy and correct electrolyte derangements.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.