SALINE / HYPEROSMOTIC LAXATIVES, MAGNESIUM SALTS, SODIUM PHOSPHATE SALTS, PEG 3350 PRODUCTS
Chemistry - Magnesium cation containing solutions of magnesium citrate, magnesium hydroxide, or magnesium sulfate act as saline laxatives. Magnesium citrate solutions contain 4.71 mEq ofmagnesium per 5 ml. Magnesium hydroxide contains 34.3 mEq of magnesium per gram and milkof magnesia contains 13.66 mEq per 5 ml. One gram of magnesium sulfate (epsom salt) containsapproximately 8.1 mEq of magnesium.
Solutions containing phosphate anions also act as saline laxatives. These solutions generallycontain monobasic and/or dibasic sodium phosphate.
Polyethylene glycol 3350 is a non-absorbable compound that acts as an osmotic agent.
Store Milk of Magnesia at temperatures less than 35°C, but do not freeze. PEG 3350 reconstituted(from powder by the pharmacy, client, clinic, etc.) solutions should be kept refrigerated and usedwithin 24 hours.
Polyethylene glycol 3350 is a non-absorbable compound that acts as an osmotic agent. By addingsodium sulfate as the primary sodium source, sodium absorption is minimized. Other electrolytes(bicarbonate, potassium and chloride) are also added so that no net change occurs with eitherabsorption or secretion of electrolytes or water in the gut.
Uses, Indications - The saline laxatives are used for their cathartic action to relieve constipation.
They are also used to reduce intestinal transit time thereby reducing the absorption of orally ingested toxicants. Polyethylene glycol 3350 balanced electrolyte solutions are used to evacuate thecolon prior to intestinal examination or surgery.
Generally, the onset of action of saline cathartics (characterized by a loose, watery stool) occurs in3-12 hours after dosing in monogastric animals and within 18 hours in ruminants.
Contraindications/Precautions - Saline cathartics are contraindicated for long-term or chronicuse. Sodium containing laxatives are contraindicated in patients with congestive heart failure orcongenital megacolon. PEG 3350 solutions are contraindicated in patients with GI obstruction, gastric retention, bowel perforation, toxic colitis or megacolon. Saline cathartics should be used withextreme caution in patients with renal insufficiency, pre-existing water-balance or electrolyteabnormalities, or cardiac disease.
Hypermagnesemia manifested by muscle weakness, ECG changes and CNS effects can occur.
Hyperphosphatemia with resultant hypocalcemia can occur with chronic overuse or overdoses ofphosphate containing products. Hypernatremia can also occur when administering sodiumphosphate solutions.
Cats may be particularly sensitive to the electrolyte imbalance effects of sodium phosphate enemasolutions and these products are not recommended for use in this species until more data areavailable.
Overdosage - Symptoms of overdosage of magnesium or phosphate containing laxatives are described above. Treatment should consist of monitoring and correcting any fluid imbalances thatoccur with parenteral fluids.
If hypermagnesemia occurs, furosemide may be used to enhance the renal excretion of the excessmagnesium. Calcium has been suggested to help antagonize the CNS effects of magnesium.
Hyperphosphatemia may cause hypocalcemia and parenteral calcium therapy may be necessary.
Magnesium laxatives should not be administered with tetracycline products
Solutions containing phosphate anions also act as saline laxatives. These solutions generallycontain monobasic and/or dibasic sodium phosphate.
Polyethylene glycol 3350 is a non-absorbable compound that acts as an osmotic agent.
Storage, Stability, Compatibility
Magnesium citrate solutions should be stored at 2-30°C.Store Milk of Magnesia at temperatures less than 35°C, but do not freeze. PEG 3350 reconstituted(from powder by the pharmacy, client, clinic, etc.) solutions should be kept refrigerated and usedwithin 24 hours.
Pharmacology - SALINE/HYPEROSMOTIC LAXATIVES, MAGNESIUM SALTS, SODIUM PHOSPHATE SALTS, PEG 3350 PRODUCTS
Although unproven, it is commonly believed that the hyperosmotic effect of thepoorly absorbed magnesium cation or phosphate anion causes water retention, stimulates stretchreceptors and enhances peristalsis in the small intestine and colon. Recent data, however, suggeststhat magnesium ions may directly decrease transit times and increase cholecystokinin release.Polyethylene glycol 3350 is a non-absorbable compound that acts as an osmotic agent. By addingsodium sulfate as the primary sodium source, sodium absorption is minimized. Other electrolytes(bicarbonate, potassium and chloride) are also added so that no net change occurs with eitherabsorption or secretion of electrolytes or water in the gut.
Uses, Indications - The saline laxatives are used for their cathartic action to relieve constipation.
They are also used to reduce intestinal transit time thereby reducing the absorption of orally ingested toxicants. Polyethylene glycol 3350 balanced electrolyte solutions are used to evacuate thecolon prior to intestinal examination or surgery.
Pharmacokinetics - SALINE/HYPEROSMOTIC LAXATIVES, MAGNESIUM SALTS, SODIUM PHOSPHATE SALTS, PEG 3350 PRODUCTS
While it is unknown how much sodium or phosphate is absorbed after administration of sodium phosphate solutions, it is estimated that up to 20% of the phosphate dosecan be absorbed. When magnesium salts are administered, up to 30% of the magnesium dose ofmagnesium can be absorbed.Generally, the onset of action of saline cathartics (characterized by a loose, watery stool) occurs in3-12 hours after dosing in monogastric animals and within 18 hours in ruminants.
Contraindications/Precautions - Saline cathartics are contraindicated for long-term or chronicuse. Sodium containing laxatives are contraindicated in patients with congestive heart failure orcongenital megacolon. PEG 3350 solutions are contraindicated in patients with GI obstruction, gastric retention, bowel perforation, toxic colitis or megacolon. Saline cathartics should be used withextreme caution in patients with renal insufficiency, pre-existing water-balance or electrolyteabnormalities, or cardiac disease.
Adverse Effects, Warnings
Except for possible cramping and nausea, adverse effects in otherwise healthy patients generally occur only with the saline cathartics with chronic use or overdoses.Hypermagnesemia manifested by muscle weakness, ECG changes and CNS effects can occur.
Hyperphosphatemia with resultant hypocalcemia can occur with chronic overuse or overdoses ofphosphate containing products. Hypernatremia can also occur when administering sodiumphosphate solutions.
Cats may be particularly sensitive to the electrolyte imbalance effects of sodium phosphate enemasolutions and these products are not recommended for use in this species until more data areavailable.
Overdosage - Symptoms of overdosage of magnesium or phosphate containing laxatives are described above. Treatment should consist of monitoring and correcting any fluid imbalances thatoccur with parenteral fluids.
If hypermagnesemia occurs, furosemide may be used to enhance the renal excretion of the excessmagnesium. Calcium has been suggested to help antagonize the CNS effects of magnesium.
Hyperphosphatemia may cause hypocalcemia and parenteral calcium therapy may be necessary.
Drug Interactions
All orally administered saline laxatives may alter the rate and extent of absorption of other drugs by decreasing intestinal transit times. The extent of these effects have notbeen well characterized for individual drugs, however.Magnesium laxatives should not be administered with tetracycline products