Cholestyramine with Diltiazem Interaction Details

Brand Names Associated with Cholestyramine

Brand Names Associated with Diltiazem

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Feb 28, 2024

Interaction Effect

Decreased diltiazem bioavailability

Interaction Summary

Concurrent administration of colestipol (a bile acid sequestrant similar to cholestyramine) with diltiazem significantly reduced the bioavailability of diltiazem and its active metabolite desacetyldiltiazem, in a crossover study of healthy subjects (n=12) given both immediate-release and sustained-release diltiazem formulations. Diltiazem bioavailability was not affected by changing the timing of dose administration for either drug[1].

Severity

Moderate

Onset

Rapid

Evidence

Theoretical

How To Manage Interaction

If co-treatment with diltiazem and cholestyramine is necessary, monitor the patient for an adequate response to diltiazem therapy and adjust the diltiazem dose if indicated. Adjustment in timing of drug co-administration did not prove helpful in maintaining diltiazem serum concentrations when diltiazem was given concomitantly with colestipol, another bile acid sequestrant.

Mechanism Of Interaction

Reduced absorption of diltiazem by non-specific binding with cholestyramine and increased gastrointestinal transit time

Literature Reports

A) Concurrent administration of diltiazem with colestipol (a bile acid sequestrant similar to cholestyramine) significantly reduced the bioavailability of diltiazem and its active metabolite desacetyldiltiazem. In a 2-way-crossover design study, healthy subjects (n=12) received single oral doses of sustained-release (SR) or immediate-release (IR) diltiazem 120 milligrams (mg) on study days 1 and 3, with a concomitant dose of colestipol 15 grams in the morning and evening of days 2 and 3. Following a 7-day washout period, subjects then crossed over to the opposite study arm. On study days 1 and 3, serial blood samples were analyzed for diltiazem and desacetyldiltiazem pharmacokinetics pre-treatment and for 24 hours after treatment. For IR-diltiazem, concomitant treatment with colestipol significantly reduced diltiazem peak concentration (Cmax) and area under the 24-hour concentration-time curve (AUC (0-24)) (by 33% and 27%, respectively; p=0.0032 and p=0.0001, respectively), and significantly increased the time to maximum diltiazem concentration (by 58%, p=0.0013). For SR-diltiazem, concurrent treatment with colestipol significantly reduced diltiazem Cmax and AUC (0-24) (by 36% and 23%, respectively; p=0.0014 and p=0.0001, respectively) and increased the time to maximum diltiazem concentration (by 30%, p=0.0070). Similar results were observed with regard to desacetyldiltiazem pharmacokinetics for both diltiazem formulations [1].

References

1 ) Turner SW, Jungbluth GL, & Knuth DW: Effect of concomitant colestipol hydrochloride administration on the bioavailability of diltiazem from immediate- and sustained-release formulations. Biopharm Drug Dispos 2002; 23:369-377.

Cholestyramine Overview

• Cholestyramine is used with diet changes (restriction of cholesterol and fat intake) to reduce the amount of cholesterol and certain fatty substances in your blood. Accumulation of cholesterol and fats along the walls of your arteries (a process known as atherosclerosis) decreases blood flow and, therefore, the oxygen supply to your heart, brain, and other parts of your body. Lowering your blood level of cholesterol and fats may help to prevent heart disease, angina (chest pain), strokes, and heart attacks.

• This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Diltiazem Overview

• Diltiazem is used to treat high blood pressure and to control angina (chest pain). Diltiazem is in a class of medications called calcium-channel blockers. It works by relaxing the blood vessels so the heart does not have to pump as hard. It also increases the supply of blood and oxygen to the heart.

• High blood pressure is a common condition, and when not treated it can cause damage to the brain, heart, blood vessels, kidneys, and other parts of the body. Damage to these organs may cause heart disease, a heart attack, heart failure, stroke, kidney failure, loss of vision, and other problems. In addition to taking medication, making lifestyle changes will also help to control your blood pressure. These changes include eating a diet that is low in fat and salt, maintaining a healthy weight, exercising at least 30 minutes most days, not smoking, and using alcohol in moderation.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.