Trometamol: Action as a Buffer Base and Excipient

Trometamol (tris hydroxymethyl aminomethane, abbreviated TRIS, brand names Addex Tham, Trometamol Köhler, and generics) is an organic base with buffering action in the physiological pH range. Unlike sodium bicarbonate, trometamol contains no sodium and no CO2, which is clinically relevant in patients with restricted lung function and sodium restriction. In Germany, trometamol is used as an infusible base for correction of severe metabolic acidosis, frequently in intensive care medicine and during resuscitation. In addition, it serves as an excipient in numerous eye drops, infusions, and injection solutions to stabilize their pH.

In clinical practice, trometamol is a straightforward but valuable tool. It does not act specifically on receptors or enzymes, but rather through the purely chemical uptake of hydrogen ions. This property makes it an established alternative or supplement to sodium bicarbonate in situations where sodium load should be minimized or intracellular buffering is required. Its use as a pH stabilizer in galenic formulations is widespread, which is why patients often unknowingly consume trometamol in many medications.

Mechanism of Action

Trometamol chemically absorbs hydrogen ions (protons) and neutralizes them to trometamol H+. This raises the pH in an acidotic environment. Unlike sodium bicarbonate, which neutralizes hydrogen ions via a reaction to water and CO2, trometamol does not produce additional carbon dioxide. In patients with restricted lung function or inadequate CO2 elimination, this property is valuable because no additional CO2 burden is created.

Another advantage is intracellular buffering action. Trometamol crosses cell membranes more effectively than sodium bicarbonate and can also neutralize acidotic shifts within the cell. In severe metabolic acidosis, such as after resuscitation or in diabetic ketoacidosis with cardiac involvement, this intracellular action is an argument for trometamol.

Pharmacokinetically, trometamol is rapidly distributed after intravenous administration and is predominantly excreted renally in unchanged form. The half-life with normal kidney function is approximately 6 to 14 hours. In renal insufficiency, trometamol accumulates significantly, requiring careful indication assessment and possible hemodialysis.

Indications

• Severe metabolic acidosis with pH below 7.1 or below 7.15 with cardiac involvement, particularly in intensive care medicine and after resuscitation
• Acidosis after cardiopulmonary bypass surgery or with massive transfusion
• Diabetic ketoacidosis with severe acidosis, as reserve therapy for refractory courses
• Buffering of infusions and eye drops as a galenic excipient
• Salicylate poisoning, in selected cases for urine alkalization
• Acidosis with hypercapnia, when CO2 burden should not be further increased by bicarbonate administration

Trometamol is not first choice for simple, mild metabolic acidosis, because treatment of the underlying cause (sepsis, shock, renal insufficiency) is the focus. pH correction through buffering alone without cause-specific therapy is insufficient.

Dosage and Administration

Adults: Dosage based on base excess and body weight. Standard calculation: dose in mmol = body weight in kg × base excess (negative value) × 0.3. Administration as 0.3 molar solution over at least one hour.

In emergency situations: 1 to 2 mmol per kg body weight initially, subsequently redose based on blood gas analysis. Maximum dose 5 to 7 mmol per kg per day.

Administration: exclusively intravenous via central venous access, because trometamol is strongly alkaline (pH of 0.3 molar solution approximately 10) and can irritate peripheral veins. Slow infusion over at least 1 hour, continuous blood gas and electrolyte monitoring.

Renal insufficiency: at eGFR below 30 ml per minute significant dose reduction or avoidance of trometamol. Accumulation can lead to hypotension and respiratory depression.

Airway management: Trometamol can cause respiratory depression if pCO2 is not controlled by adequate breathing or ventilation. In spontaneously breathing patients, trometamol administration is therefore critical.

Contraindications: respiratory insufficiency with uncontrolled hypercapnia without ventilation, severe renal insufficiency with anuria, pregnancy and breastfeeding (relative).

Adverse Effects

Frequent: respiratory depression with too rapid infusion or in spontaneously breathing patients, hypoglycemia, hyperkalemia.

Occasional: hypotension, bradycardia, local irritation at injection site, phlebitis with peripheral administration.

Rare: tissue necrosis from extravasation, allergic reactions, acute respiratory insufficiency, acute hypotension with very rapid infusion.

With renal insufficiency: accumulation with progressive sedation, hyperkalemia, and respiratory depression. Dialysis as treatment of choice for accumulation.

In neonates: increased risk for hypoglycemia and respiratory depression. Use in pediatrics only under specialized guidance.

Drug Interactions

• Acidic solutions: Trometamol solution is alkaline (pH approximately 10) and pharmaceutically incompatible with acidic substances. No direct mixing in the same infusion line.
• Potassium containing infusions: increased risk of hyperkalemia, particularly with renal insufficiency.
• Lithium: Trometamol may alter lithium levels, clinically rarely relevant.
• Salicylates: in salicylate poisoning, trometamol may alter renal elimination, combination sensible in specific indications.
• Corticosteroids: no direct interactions, but additive hyperglycemia and hyperkalemia tendency in specific constellations.
• Sympathomimetics: no relevant interactions.

Special Information

Pregnancy: Data limited. Use only in vitally indicated acute situations and after individual consultation. Breastfeeding: after brief acute use, breastfeeding can usually be continued, individual assessment.

Neonates and infants: Use only in specialized neonatal or pediatric intensive care settings, due to risk of hypoglycemia and respiratory depression.

Before use: Blood gas analysis, electrolytes, glucose, renal function, respiratory function. In spontaneously breathing patients have airway management ready.

Monitoring: continuous respiratory and circulatory monitoring, regular blood gas analysis, electrolytes, and glucose.

Extravasation protection: Trometamol solution is strongly alkaline and can cause tissue necrosis with extravasation. Secure central venous access is mandatory. If extravasation suspected, stop infusion, elevate extremity, local therapy.

Indication assessment: Trometamol is always symptomatic therapy. The cause of acidosis (sepsis, shock, renal insufficiency, ketoacidosis) must be treated in parallel, otherwise sustained improvement will not occur.

Comparison with sodium bicarbonate: Trometamol without sodium and CO2 burden is advantageous in hypercapnia, heart failure, and sodium restriction. Sodium bicarbonate is less expensive and first choice in most standard indications.

Driving ability: not relevant due to acute use in the clinic.

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Frequently Asked Questions

Sources

• Gelbe Liste, Trometamol active ingredient profile
• BfArM, Federal Institute for Drugs and Medical Devices
• AWMF, Guidelines on sepsis, resuscitation, and intensive care medicine
• German Society for Anesthesiology and Intensive Care Medicine