What Medications Should Not Be Taken with Glycine?

October 8, 2025 •

4 min read

According to a study published by WebMD, it is explicitly advised that individuals taking the antipsychotic medication clozapine (Clozaril) should not combine it with glycine, as this may decrease the medication's effectiveness. Understanding what medications should not be taken with glycine is a vital step in preventing potentially dangerous drug interactions and adverse health effects.

Quick Summary

Glycine supplements can cause critical interactions with specific medication classes, including antipsychotics like clozapine, central nervous system depressants, and blood pressure-lowering drugs. Always consult a healthcare provider before use.

Key Points

Avoid Glycine with Clozapine: Do not take glycine supplements if you are on the antipsychotic medication clozapine (Clozaril), as it may reduce the drug's effectiveness.
Beware of Additive Sedation: Glycine's calming properties can be compounded by other central nervous system (CNS) depressants like benzodiazepines and muscle relaxants, leading to excessive drowsiness and a higher risk of side effects.
Monitor Blood Pressure: Individuals taking medication for high blood pressure should be cautious with glycine, as it may lower blood pressure further, potentially causing hypotension.
Inform Your Doctor about All Medications: Due to complex interactions with various drug classes, including antidepressants and immunosuppressants, always inform your healthcare provider about all medications and supplements you are taking.
Seek Professional Medical Advice: Never self-medicate or combine supplements with prescription drugs without consulting a healthcare professional. They can assess your risk and provide guidance based on your specific health needs.
Use Caution with Digoxin: The combination of glycine and medications in the digoxin family could increase the risk or severity of adverse effects.
Vulnerable Populations Need Extra Care: Special caution should be taken by pregnant or breastfeeding women, individuals with kidney or liver disease, and those with a history of stroke.

Glycine is a non-essential amino acid naturally produced by the body and found in many protein-rich foods. As a dietary supplement, it is used to support various functions, including improving sleep quality, enhancing muscle recovery, and potentially benefiting neurological symptoms. However, like many supplements, glycine can have complex and sometimes serious interactions with prescription medications. It is critical for individuals considering supplementation to be aware of these potential risks and always consult a healthcare provider.

The Critical Interaction with Clozapine (Clozaril)

One of the most well-documented and cautioned interactions is between glycine and the antipsychotic medication clozapine, often sold under the brand name Clozaril. Clozapine is a powerful drug used to treat severe schizophrenia, particularly in patients who have not responded to other treatments. Research and clinical observations have consistently shown that taking glycine alongside clozapine might significantly decrease the effectiveness of the antipsychotic.

Decreased Efficacy: The exact mechanism of this interaction is not fully understood, but it is clear that for some reason, glycine reduces the therapeutic benefits of clozapine. This can be particularly dangerous for individuals whose condition is managed by this medication. One study found that adding glycine to clozapine therapy provided no benefit for negative symptoms in patients with treatment-resistant schizophrenia and may even have reduced the effectiveness of clozapine.
Worsening Symptoms: Some evidence suggests that adding glycine to a clozapine regimen may worsen symptoms for some individuals. Given the severity of the condition clozapine treats, this is a very high-risk interaction that requires strict avoidance.

Potentiating Effects with Central Nervous System (CNS) Depressants

Glycine acts as an inhibitory neurotransmitter in the brain, which means it helps to calm neural activity and promote relaxation. Because of this calming effect, combining glycine with other CNS depressants can lead to an additive effect, increasing the risk of excessive sedation, drowsiness, and respiratory depression.

Medications in this category include:

Benzodiazepines: A class of drugs used to treat anxiety, insomnia, and seizures (e.g., diazepam, lorazepam).
Muscle Relaxants: Medications like baclofen, which are used to treat muscle spasms, may have their sedative effects enhanced by glycine.
Sedatives and Hypnotics: This includes any medication designed to induce sleep or sedation. The combination could lead to heightened drowsiness.

Interactions with Antidepressants

Several studies, primarily in animal models, have investigated the complex relationship between glycine and various antidepressants. Research indicates that certain antidepressants, including fluoxetine (a Selective Serotonin Reuptake Inhibitor) and tianeptine, may inhibit glycine's action on specific ion currents in the brain. This suggests a potentially altered interaction with the brain's neurotransmitter systems, though the clinical significance in humans is still under investigation. Some evidence points to a complex interplay depending on the antidepressant type and the glycine receptor function. Given these findings, medical guidance is crucial when combining glycine with any antidepressant.

Effects on Blood Pressure Medications

Glycine may possess a blood pressure-lowering effect. For individuals already taking antihypertensive medications, this could lead to dangerously low blood pressure (hypotension). Close monitoring of blood pressure is essential if combining glycine with any of the following:

Diuretics
Beta-blockers
ACE Inhibitors
Calcium Channel Blockers

Less Common but Notable Interactions

While less extensively studied, other potential interactions have been reported that require caution:

Digoxin: Medications in the digoxin family (like acetyldigitoxin) may have increased adverse effects when combined with glycine.
Immunosuppressants: Glycine has shown anti-inflammatory properties and can modulate immune responses, particularly in animal studies involving cyclosporine. While some studies suggest a protective effect against cyclosporine-induced toxicity, the potential for altered immune function means this combination should only be managed by a healthcare professional.
Other Drug Classes: Some lists mention potential interactions with anticoagulants, steroids (like prednisolone), and certain pain relievers like aspirin. The specifics of these interactions warrant further investigation and medical advice.

Comparison of Glycine Interactions


Medication Class	Specific Medication Examples	Potential Interaction	Severity
Antipsychotics	Clozapine (Clozaril)	Glycine may decrease the medication's effectiveness.	High Risk
CNS Depressants	Benzodiazepines, Muscle Relaxants, Sedatives	Additive sedative effects, increasing drowsiness and risk of respiratory depression.	Moderate to High Risk
Blood Pressure Drugs	Beta-blockers, Diuretics	Glycine's blood pressure-lowering effect may potentiate antihypertensive drugs, causing hypotension.	Moderate Risk
Antidepressants	Fluoxetine, Tianeptine	Potential modulation of neurotransmitter systems and altered drug efficacy.	Caution Advised
Immunosuppressants	Cyclosporine	Complex interactions affecting immune response; potentially alters toxicity.	Caution Advised
Digoxin	Acetyldigitoxin, Digitoxin	Potential for increased adverse effects.	Caution Advised

Consulting a Healthcare Professional

Given the complexity and potential severity of these interactions, it is always crucial to consult a healthcare provider before taking glycine, especially if you are on any other medications. They can assess your individual health status, review your current medication list, and provide personalized guidance on the safety of glycine supplementation.

Conclusion

While glycine is a generally safe and beneficial amino acid for many, its use with specific medications poses significant risks that should not be overlooked. The interaction with clozapine is particularly critical, potentially undermining the treatment for a serious condition. Likewise, combining it with CNS depressants can lead to excessive sedation, and with blood pressure medications, it can cause dangerous hypotension. Always disclose any supplement use to your doctor, including glycine, to ensure your health and safety. Prudence and professional medical advice are your best allies in navigating these potential drug interactions.

Frequently Asked Questions

No, you should not take glycine if you are taking clozapine. Studies have shown that glycine can decrease the effectiveness of clozapine, which is a serious risk for individuals with schizophrenia.

Yes, glycine may interact with anti-anxiety medications, particularly benzodiazepines, and other central nervous system (CNS) depressants. This is because both can cause sedation, and combining them could lead to excessive drowsiness or other side effects.

You should consult your doctor before combining glycine with blood pressure medication. Glycine can have a blood pressure-lowering effect, which might enhance the effects of antihypertensive drugs and cause hypotension.

Research suggests antidepressants may inhibit glycine's action on certain neural ion currents, though the clinical implications in humans are not fully understood. Due to this complex interaction, medical supervision is recommended.

The interaction between glycine and immunosuppressants like cyclosporine is complex and requires medical oversight. While animal studies suggest glycine can mitigate some side effects, it may also alter the medication's effect on the immune system.

Yes, individuals with severe psychiatric disorders (especially if taking clozapine), those with kidney or liver disease, and people who have recently had a stroke should use caution and consult a doctor before taking glycine.

If you suspect an adverse interaction or experience any concerning side effects, stop taking the glycine supplement immediately and contact your healthcare provider for advice.