Usage
- Glycine is prescribed as an adjunct therapy for schizophrenia to help alleviate negative symptoms in patients who don’t respond well to conventional antipsychotic medications. It’s also used in urology to improve urine storage symptoms. It has shown promise in protecting against doxorubicin-induced heart toxicity. It may also be used in specific clinical settings like during intubation, surgical procedures, or in the ICU when rapid reductions in core body temperature is required.
- Pharmacological Classification: Amino acid, neurotransmitter modulator.
- Mechanism of Action: Glycine acts as an inhibitory neurotransmitter in the central nervous system, primarily in the brainstem and spinal cord. It also acts as a co-agonist at NMDA receptors, thereby modulating glutamatergic neurotransmission. This dual action is believed to contribute to its therapeutic effects in schizophrenia.
Alternate Names
How It Works
- Pharmacodynamics: Glycine’s primary effect is on the central nervous system, where it modulates neuronal excitability. By acting on NMDA receptors, it may enhance cognitive function and reduce negative symptoms in schizophrenia. Peripherally, glycine contributes to various metabolic processes, including collagen synthesis and detoxification.
- Pharmacokinetics: Glycine is readily absorbed from the gastrointestinal tract. It is metabolized primarily in the liver through transamination to serine and deamination to ammonia, which is then converted to urea. Glycine is excreted by the kidneys.
- Mode of Action: Glycine acts as an inhibitory neurotransmitter by binding to glycine receptors, leading to chloride influx and hyperpolarization of postsynaptic neurons. As an NMDA receptor co-agonist, it facilitates glutamate binding and enhances excitatory neurotransmission.
- Elimination Pathways: Glycine is primarily eliminated through renal excretion. A smaller portion is metabolized in the liver.
Dosage
Standard Dosage
Adults:
- For schizophrenia: 0.4-0.8 g/kg daily in divided doses, starting at 4 g daily and increasing by 4 g per day until the effective dose is reached. Daily doses up to 6 grams for up to 4 weeks are generally considered possibly safe.
- For other uses: 2-5 grams daily.
Children:
- Safety and efficacy in children have not been established for all uses. For isovaleric acidemia: 50 mg/kg three times daily. The dose may be increased to a maximum of 250 mg/kg/day during acute episodes.
Special Cases:
- Elderly Patients: Dose adjustments may be necessary based on renal function.
- Patients with Renal Impairment: Dose reduction is recommended.
- Patients with Hepatic Dysfunction: Use with caution due to potential for hyperammonemia.
- Patients with Comorbid Conditions: Use with caution in patients with cardiovascular or pulmonary disease.
Clinical Use Cases
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: High doses of glycine (e.g. 0.5 g/kg body weight) may be required for specialized applications such as inducing therapeutic hypothermia or mitigating reperfusion injury, administered either enterally or intravenously. This is typically done under strict medical supervision in critical care settings.
Dosage Adjustments: Adjustments may be necessary for patients with renal or hepatic impairment.
Side Effects
Common Side Effects:
- Mild gastrointestinal upset (e.g., nausea, stomach discomfort).
Rare but Serious Side Effects:
- Hyperammonemia (in patients with hepatic impairment)
- Hyponatremia
- Coma
- Allergic reactions (rare)
Contraindications
- Anuria
- Severe liver or kidney impairment
- Hypersensitivity to glycine
Drug Interactions
- Clozapine: Glycine may reduce the effectiveness of clozapine.
- Aspirin: Contraindicated in patients with isovaleric acidemia receiving glycine.
Pregnancy and Breastfeeding
- Safety during pregnancy and breastfeeding has not been established. Avoid use unless clearly needed and under medical supervision.
Drug Profile Summary
- Mechanism of Action: Inhibitory neurotransmitter, NMDA receptor co-agonist.
- Side Effects: Generally well-tolerated; mild gastrointestinal upset is possible.
- Contraindications: Anuria, severe liver/kidney impairment, hypersensitivity.
- Drug Interactions: Clozapine, aspirin.
- Pregnancy & Breastfeeding: Avoid use unless clearly necessary under medical supervision.
- Dosage: Varies depending on indication and patient factors.
- Monitoring Parameters: Renal and hepatic function, electrolyte levels (especially sodium).
Popular Combinations
- Glycine is sometimes used in combination with other antipsychotic medications for schizophrenia.
Precautions
- General Precautions: Assess renal and hepatic function before starting therapy.
- Specific Populations: Exercise caution in pregnant/breastfeeding women, children, and the elderly.
- Lifestyle Considerations: Alcohol consumption may exacerbate potential liver-related side effects.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Glycine?
A: The dosage of glycine varies depending on the indication. For schizophrenia, it can range from 0.4-0.8 g/kg daily. For other indications like improving sleep quality, lower doses of 2-5 grams daily may be sufficient.
Q2: How does Glycine work in schizophrenia?
A: Glycine acts as an inhibitory neurotransmitter and NMDA receptor co-agonist, modulating glutamatergic neurotransmission. This mechanism is thought to contribute to its therapeutic effects on negative symptoms.
Q3: What are the common side effects of Glycine?
A: Glycine is generally well-tolerated. Mild gastrointestinal upset is the most common side effect.
Q4: Is Glycine safe during pregnancy?
A: The safety of glycine during pregnancy has not been established. Avoid use unless clearly needed under medical supervision.
Q5: Can Glycine interact with other medications?
A: Yes, glycine can interact with clozapine, potentially reducing its effectiveness. It also interacts with aspirin in specific clinical contexts (isovaleric acidemia).
Q6: What are the contraindications for Glycine use?
A: Contraindications include anuria, severe liver/kidney disease, and hypersensitivity to glycine.
Q7: How is Glycine eliminated from the body?
A: Glycine is primarily excreted by the kidneys. Some metabolism occurs in the liver.
Q8: What should be monitored in patients taking Glycine?
A: Monitor renal and hepatic function, as well as electrolyte levels (especially sodium), especially when using higher doses for therapeutic purposes.
Q9: What precautions should be taken when administering high-dose Glycine in critical care settings?
A: High-dose Glycine should be administered under close medical supervision with careful monitoring for potential side effects such as hyponatremia and cardiovascular instability. Fluid and electrolyte balance should be maintained. Dosage and administration rate should be titrated based on patient response and tolerance.
Q10: Is Glycine available as a generic medication?
A: Yes, glycine is available as a generic medication and is also a component of some dietary supplements. As of today, February 16, 2025, the FDA is reviewing the regulatory status of NAC in dietary supplements. This review may impact future availability.
