Hydroxychloroquine, sold under the brand name Plaquenil, is a medication used to manage autoimmune conditions like lupus and rheumatoid arthritis, and it is also prescribed for the prevention and treatment of malaria. The effectiveness and safety of a medication can be influenced by other substances, a process known as a drug interaction. When one drug alters another’s effects, it can decrease efficacy or increase the risk of adverse effects. Understanding these potential interactions is a fundamental part of using the medication safely.
Interactions Affecting Heart Rhythm
A significant concern with hydroxychloroquine is its potential to affect the heart’s electrical system. Specifically, it can cause a condition known as QT interval prolongation. This is a delay in the heart’s electrical system recharging after each beat. For most, this change is minor, but it can create a risk for a serious irregular heartbeat called Torsades de Pointes. The risk of this arrhythmia increases when hydroxychloroquine is taken with other medications that also prolong the QT interval, as the effects are additive.
Several classes of common medications carry this same risk and require careful consideration. Certain antibiotics, particularly macrolides like azithromycin and clarithromycin, as well as fluoroquinolones such as ciprofloxacin, are known to prolong the QT interval. Patients should be aware of this potential issue when prescribed these antibiotics.
The risk extends to medications used for mental health conditions. Specific antidepressants, including the selective serotonin reuptake inhibitors (SSRIs) citalopram and escitalopram, can have this effect on the heart’s rhythm. Many antipsychotic medications, used to treat conditions like schizophrenia and bipolar disorder, also share this property. Combining them with hydroxychloroquine necessitates careful evaluation by a physician.
A class of drugs called antiarrhythmics, which are prescribed specifically to treat existing heart rhythm disorders, can also interact. Drugs like amiodarone are QT-prolonging agents. The co-administration of these with hydroxychloroquine is avoided unless necessary and conducted under close medical supervision, involving regular heart monitoring.
Effects on Diabetes and Seizure Medications
Beyond its effects on heart rhythm, hydroxychloroquine can influence how the body manages blood sugar. The medication itself can lower glucose levels, which introduces a risk of hypoglycemia (dangerously low blood sugar). This effect becomes much more pronounced when a person is also taking medications designed to treat diabetes. The combined action can lead to an amplified reduction in blood sugar.
The risk is particularly heightened for individuals using insulin or oral diabetes drugs like sulfonylureas and metformin. The synergistic effect means that a standard dose of a diabetes medication might become too powerful, leading to symptoms of hypoglycemia such as shakiness, confusion, and sweating. Individuals with diabetes who start taking hydroxychloroquine must monitor their blood sugar levels closely. Adjustments to their diabetes medication dosage may be necessary under a doctor’s guidance.
Hydroxychloroquine may also interact with medications used to control seizures, known as anticonvulsants. The drug has been observed to lower the seizure threshold. This means it could make it easier for a seizure to occur in susceptible individuals. This interaction could undermine the effectiveness of anticonvulsant medications like carbamazepine, phenobarbital, and phenytoin. Patients with a history of seizures need to discuss this potential interaction with their healthcare provider.
Interactions Affecting Drug Absorption and Concentration
The way hydroxychloroquine is absorbed and processed by the body can be altered by other substances, affecting its concentration and efficacy. A common interaction involves over-the-counter products used for indigestion and diarrhea. Antacids and kaolin-containing preparations can bind to hydroxychloroquine in the stomach and intestines. This prevents the drug from being fully absorbed, reducing its effectiveness. To avoid this, it is recommended to separate the administration of hydroxychloroquine and these products by at least four hours.
Another notable interaction occurs with digoxin, a medication used to treat certain heart conditions like heart failure and atrial fibrillation. Hydroxychloroquine can interfere with the body’s ability to clear digoxin, leading to an increase in digoxin levels in the blood. Since digoxin has a narrow therapeutic window, even a small increase in its concentration can lead to toxicity, manifesting as nausea, vision changes, and a slow heart rate. Patients on this combination require careful monitoring of their digoxin blood levels.
The concentration of hydroxychloroquine itself can be affected by other drugs. For instance, cimetidine, a medication used to reduce stomach acid, can inhibit the enzymes responsible for breaking down hydroxychloroquine in the body. This blockage can cause levels of hydroxychloroquine to rise, increasing the risk of side effects.
Strategies for Safe Medication Management
Navigating the complexities of drug interactions requires a proactive approach to medication management. The primary step for any patient is to maintain and share a complete list of all substances they are taking. This list must include all prescription medications, over-the-counter drugs, and any herbal supplements or vitamins. This record should be presented to the prescribing doctor and pharmacist for a full safety review.
The pharmacist plays a role in this process, acting as a checkpoint for potential interactions. When a new prescription is filled, the pharmacist’s software systems can flag potential conflicts. This provides an opportunity for consultation and for the pharmacist to contact the prescribing physician to discuss alternatives. Patients should view their pharmacist as an accessible and knowledgeable resource.
Healthcare providers may recommend specific monitoring protocols based on an individual’s medications and health status. This could involve periodic electrocardiograms (ECGs) to check the heart’s QT interval or regular blood tests. No patient should ever start or stop a medication without first consulting their healthcare professional. Be aware of symptoms that could indicate a serious drug interaction and seek immediate medical attention if they occur:
- Fainting
- A racing or irregular heartbeat
- Severe dizziness
- Signs of very low blood sugar