AMINO ACIDS
Clinical safety rating
cautionComprehensive clinical and safety monograph for AMINO ACIDS (AMINO ACIDS).
Amino acids are building blocks for protein synthesis and serve as precursors for neurotransmitters, hormones, and other nitrogenous compounds. They modulate nitrogen balance and support cellular repair and growth.
| Metabolism | Amino acids are metabolized primarily in the liver via transamination, deamination, and urea cycle. Specific pathways exist for each amino acid; excess nitrogen is converted to urea. |
| Excretion | Renal: >95% as amino acids and metabolites, primarily reabsorbed; <5% unchanged. Fecal/biliary: negligible (<1%). |
| Half-life | Variable; endogenous amino acids: 10–30 min for clearance from plasma; administered doses: distribution half-life ~5–10 min, terminal elimination half-life ~15–30 min, reflecting rapid metabolic utilization and renal reabsorption. |
| Protein binding | Minimal for most amino acids (<10%); albumin and globulins bind tryptophan and aromatic amino acids (~80–90% for tryptophan). |
| Volume of Distribution | 0.4–0.6 L/kg (total body water); reflects equilibration with intracellular and extracellular fluid compartments. |
| Bioavailability | Oral: ~90–100% (active transport across intestinal mucosa); IV: 100%. |
| Onset of Action | IV: Immediate (within seconds to minutes); oral: 30–60 min (dependent on gastric emptying and absorption). |
| Duration of Action | IV: Metabolic effects persist 1–2 hours post-infusion; oral: 3–4 hours, influenced by protein synthesis rates and amino acid pool dynamics. |
| Molecular Weight | Variable (range 75-204 Da for standard amino acids) |
1-2 g/kg/day as continuous IV infusion or as a component of parenteral nutrition.
| Dosage form | INJECTABLE |
| Renal impairment | For GFR <30 mL/min: reduce dose to 0.5-1 g/kg/day; monitor serum amino acids and nitrogen balance. |
| Liver impairment | Child-Pugh B or C: avoid standard formulations; use branched-chain amino acid (BCAA)-enriched solutions at 0.8-1.2 g/kg/day. |
| Pediatric use | 0.5-2 g/kg/day IV; titrate based on age, growth, and metabolic needs. |
| Geriatric use | Initiate at 0.8 g/kg/day IV, adjust based on renal function and nitrogen balance; monitor for fluid overload. |
| 1st trimester | Amino acids are essential for fetal development; supplementation is generally considered safe when used to correct deficiency or provide parenteral nutrition. No known teratogenicity when administered appropriately. |
| 2nd trimester | Amino acids are essential for fetal development; supplementation is generally considered safe when used to correct deficiency or provide parenteral nutrition. |
| 3rd trimester | Amino acids are essential for fetal development; supplementation is generally considered safe when used to correct deficiency or provide parenteral nutrition. |
Clinical note
Comprehensive clinical and safety monograph for AMINO ACIDS (AMINO ACIDS).
| Placental transfer | Amino acids are actively transported across the placenta by specific transporters; concentrations in fetal blood are typically higher than maternal blood. Endogenous amino acids readily cross. |
| Breastfeeding | Amino acids are normal components of breast milk. Supplementation is considered compatible with breastfeeding; maternal intake can increase milk amino acid concentrations but no adverse effects reported. |
| Lactation Rating | L1 |
| Teratogenic Risk | Amino acids are essential nutrients; at physiologic doses, no teratogenic risk is established. At supraphysiologic doses, theoretical risk of metabolic imbalance exists. No trimester-specific human data; animal studies show no teratogenicity at standard doses. |
| Fetal Monitoring | Monitor maternal serum amino acid levels, ammonia if parenteral administration; fetal growth ultrasound if prolonged high-dose therapy. Assess for metabolic acidosis, hyperammonemia, and electrolyte imbalances. |
| Fertility Effects | No adverse effects on fertility reported at physiologic doses. In malnutrition, supplementation may restore normal reproductive function. High-dose or imbalanced amino acid supplementation may disrupt hormonal regulation. |
■ FDA Black Box Warning
Patients receiving amino acid infusions should be monitored for metabolic acidosis, hyperammonemia, and renal function impairment. Solutions with electrolytes should not be used in patients with severe electrolyte imbalances.
| Serious Effects |
Inborn errors of amino acid metabolism (e.g., phenylketonuria without metabolic control)Severe hepatic failure with hyperammonemiaSevere metabolic acidosis
| Precautions | Use with caution in patients with renal impairment, hepatic failure, heart failure, or metabolic acidosis. Monitor serum electrolytes, blood urea nitrogen, and ammonia levels. Avoid rapid infusion to prevent hyperosmolarity and venous thrombosis. |
| Food/Dietary | No significant food interactions; however, enteral nutrition should be managed to avoid excessive protein intake. Patients with phenylketonuria must avoid phenylalanine-containing amino acid solutions. |
| Clinical Pearls | Amino acid infusions should be administered via central line if osmolarity > 900 mOsm/L to prevent thrombophlebitis. Monitor serum ammonia and BUN in patients with hepatic or renal impairment. Use with caution in patients with inborn errors of amino acid metabolism. |
| Patient Advice | This medication provides essential building blocks for protein synthesis. · Report any signs of allergic reaction such as rash, itching, or difficulty breathing. · Inform your doctor if you have liver or kidney disease. · Do not take other protein supplements unless directed by your healthcare provider. |
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