What happens if you take gabapentin and losartan together?

October 9, 2025 •

4 min read

Animal studies suggest that taking gabapentin and losartan together can significantly increase gabapentin's plasma and brain concentrations. This pharmacokinetic interaction can lead to a heightened risk of central nervous system side effects, such as dizziness, drowsiness, and motor impairment, highlighting the need for cautious use and medical supervision when combining these two drugs.

Quick Summary

Combining gabapentin and losartan can amplify gabapentin's effects, potentially increasing the risk of side effects like dizziness and drowsiness. Enhanced monitoring and dosage adjustments by a healthcare provider are often necessary to manage potential interactions and side effects.

Key Points

Increased Gabapentin Levels: Losartan can increase the concentration of gabapentin in the body, amplifying its effects and side effects.
Higher Risk of Dizziness and Drowsiness: The combination of both drugs, which individually cause sedation, significantly increases the risk of excessive dizziness and drowsiness.
Potential for Motor Impairment: Animal studies suggest a risk of impaired motor coordination when combining these drugs, which could increase the risk of falls.
Risk of Low Blood Pressure (Hypotension): Both medications lower blood pressure, and their combined effect requires careful monitoring to prevent symptomatic hypotension.
Careful Monitoring for Kidney Function: Since gabapentin is cleared by the kidneys, patients with renal impairment must be closely monitored, as losartan also affects kidney function.
Requires Medical Supervision: The interaction necessitates dosage adjustments and close monitoring by a healthcare professional to ensure patient safety.
Avoid Driving: Due to the heightened risk of sedation and motor impairment, patients should be cautious about operating vehicles or machinery until they know how the combination affects them.

Understanding Gabapentin and Losartan Individually

To comprehend the interaction between gabapentin and losartan, it is essential to first understand their individual functions. Gabapentin is an anticonvulsant medication primarily prescribed to manage certain types of seizures and treat nerve pain, such as post-herpetic neuralgia. It works by affecting nerve activity and calming overactive nerve cells. Common side effects of gabapentin include dizziness, drowsiness, and fatigue.

Losartan, on the other hand, is an angiotensin II receptor blocker (ARB) used to treat high blood pressure (hypertension) and heart failure. It functions by relaxing blood vessels, which allows for easier blood flow and reduces blood pressure. Losartan is also used to protect the kidneys in patients with type 2 diabetes and hypertension. Some common side effects of losartan include dizziness, tiredness, and potential effects on kidney function.

The Pharmacokinetic Interaction: Increased Gabapentin Levels

The most significant interaction identified between these two medications is pharmacokinetic in nature. Research, specifically animal studies, has demonstrated that losartan can increase the plasma and brain concentrations of gabapentin. This is thought to be due to losartan's influence on gabapentin's absorption or metabolism. A higher concentration of gabapentin in the body means its therapeutic and side effects are enhanced. This is especially important for patients who are susceptible to the dose-dependent side effects of gabapentin or have impaired kidney function.

Potential Side Effects of Combining Gabapentin and Losartan

Combining gabapentin and losartan can lead to a range of potential side effects, primarily due to the increased levels and effects of gabapentin.

Heightened Central Nervous System (CNS) Effects

Increased Dizziness and Drowsiness: Both drugs can cause dizziness and drowsiness individually. When combined, this effect is often additive, meaning the risk of experiencing significant sedation is much higher.
Motor Impairment: Animal studies have shown that the combined use of gabapentin and losartan can cause motor coordination issues. While human data is limited, healthcare providers should be aware of this potential risk for falls, particularly in older adults.

Cardiovascular and Kidney Concerns

Hypotension (Low Blood Pressure): Both medications contribute to lowering blood pressure. Patients starting this combination or undergoing a dosage change may be at a greater risk of hypotension, which can cause severe dizziness, lightheadedness, and fainting.
Kidney Function Alterations: Gabapentin is eliminated from the body via the kidneys. Patients with pre-existing kidney impairment need careful dosage adjustment for gabapentin. The combination of gabapentin and losartan, which is known to affect renal function, necessitates close monitoring of kidney health.

Other Potential Side Effects

Increased Risk of Misuse: The increased bioavailability of gabapentin when taken with losartan could exacerbate the potential for gabapentin misuse.
Changes in Blood Pressure: A specific case study noted a hypertensive reaction in a patient taking gabapentin and losartan, along with quetiapine, indicating complex interactions can occur.

Management and Clinical Considerations

Managing patients on both gabapentin and losartan requires a proactive and vigilant approach from healthcare professionals. The risks of combining these medications are real, and careful monitoring is necessary to ensure patient safety.

Monitor for Enhanced Side Effects: The prescribing doctor should closely watch for signs of increased dizziness, excessive drowsiness, and impaired motor skills, especially during the initial phase of treatment or following dose adjustments.
Adjust Dosage: Since losartan can increase gabapentin concentrations, a healthcare provider might need to prescribe a lower dose of gabapentin than would typically be used alone.
Evaluate Alternatives: If the patient experiences significant side effects, the doctor might consider alternative medications. Animal studies have indicated that other antihypertensive drugs like captopril or enalapril do not have the same interaction effect on gabapentin's anticonvulsant activity.
Educate the Patient: Informing patients about the potential for increased sedation and dizziness is crucial. They should be advised to avoid activities requiring mental alertness, such as driving, until they understand how the combination affects them.
Regular Kidney Function Tests: Regular blood and urine tests are important, particularly for patients with any pre-existing kidney disease, to monitor for any adverse effects on renal function.

Comparison of Gabapentin and Losartan


Feature	Gabapentin	Losartan
Drug Class	Anticonvulsant, Gabapentinoid	Angiotensin II Receptor Blocker (ARB)
Primary Use	Seizure control, neuropathic pain, restless legs syndrome	Hypertension, heart failure, diabetic kidney disease
Mechanism	Affects nerve activity, calms overactive nerve cells	Blocks angiotensin II receptors, relaxing blood vessels
Key Side Effects	Dizziness, drowsiness, fatigue, ataxia, confusion	Dizziness, fatigue, headache, hypotension
Risk of Sedation	High	Low (additive effect with gabapentin)
Kidney Effect	Excreted by kidneys, dosage adjustment needed for renal impairment	Can affect kidney function, especially in long-term use

Conclusion

While gabapentin and losartan are frequently prescribed medications for different conditions, their co-administration requires careful consideration due to a significant pharmacokinetic interaction. Research indicates that losartan can increase gabapentin levels in the body, which can heighten the risk of central nervous system side effects such as dizziness, drowsiness, and motor impairment. Furthermore, the combined blood pressure-lowering effects increase the risk of hypotension, and cautious management is necessary for patients with pre-existing kidney issues. Therefore, it is crucial for patients taking both medications to be under close medical supervision. A healthcare provider can determine the appropriate dosage adjustments and monitor for potential adverse effects to ensure the safety and efficacy of the treatment plan. Patients should always inform their doctor about all medications they are taking, including over-the-counter drugs and supplements.

Important Medical Disclaimer

The information provided is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. For more authoritative information, consult medical organizations like the U.S. National Library of Medicine.

Frequently Asked Questions

Yes, but only under the close supervision of a healthcare provider. The combination has a known drug interaction where losartan can increase the levels of gabapentin in the body, leading to a higher risk of side effects. Your doctor will need to manage and adjust your dosages carefully.

The most notable side effects are increased dizziness, drowsiness, and fatigue. These effects are more pronounced than with either medication alone due to the additive nature of their sedative properties.

Yes, both gabapentin and losartan can lower blood pressure. Taking them together increases the risk of hypotension (low blood pressure), which can cause lightheadedness or fainting.

Studies suggest that losartan affects the pharmacokinetics of gabapentin, leading to higher plasma and brain concentrations. This means more of the gabapentin medication is available in your system, enhancing its effects and side effects.

If you experience severe dizziness or sedation, you should contact your doctor immediately. Do not drive or operate machinery until the symptoms resolve. Your doctor may need to adjust your medication dosages.

Patients with kidney problems are at higher risk. Gabapentin is cleared by the kidneys, so impaired renal function can cause the drug to build up. Since both medications affect the kidneys, close monitoring and potential dosage adjustments are critical.

Yes, animal studies have shown that the combination can cause motor impairment, affecting coordination. This potential effect is a key reason for caution, especially in older adults who are already at risk for falls.

Not necessarily. Animal studies have shown that other similar antihypertensives like captopril or enalapril did not affect gabapentin's anticonvulsant activity in the same manner as losartan, suggesting the interaction is specific to losartan.