Why you should take diltiazem on an empty stomach

Diltiazem is a generic medication called a calcium channel blocker that can help manage blood pressure. If you’ve been prescribed certain forms of diltiazem, you might have been advised to take it on an empty stomach.

This is because taking controlled-release or extended-release (ER) diltiazem on an empty stomach typically helps improve its absorption. This means your body takes it into the bloodstream more easily, so it should be more effective.

Similarly, consuming certain foods or substances with these forms of diltiazem could lower its absorption, making the drug less effective.

So it’s important to discover what can affect the effectiveness and metabolism of diltiazem to make sure it’s working as well.

How is it absorbed?

You’ll typically take diltiazem (Cardizem) orally as an ER or immediate-release (IR) capsule. The IR form of diltiazem — true to its name — gets to work straight away and should have a quick effect. But this form of diltiazem leaves your bloodstream relatively quickly, so you usually need to take more doses throughout the day.

The ER capsules (diltiazem ER) provide a controlled and steady release of the medication into the blood for up to 24 hours, meaning you may only need to take it once or twice per day.

Diltiazem is properly absorbed from your stomach or intestines (gastrointestinal system) when you swallow it, but it undergoes something called first-pass metabolism in the liver. This is where the liver changes the drug before it reaches your bloodstream, usually lowering its overall concentration and effectiveness.

After the first-pass metabolism, plasma proteins bind to diltiazem and distribute them all over the body through the bloodstream.

Certain factors, including diet and alcohol, may affect the absorption rate of diltiazem.

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How does food affect it?

Food does not typically affect the blood concentration or efficacy of diltiazem. So taking it on an empty stomach isn’t necessary, and doctors usually won’t advise you to do this.

But research from 2023 suggests that if you take ER diltiazem with both fatty foods and alcohol, it may increase its absorption rate from the intestines. When this happens, the blood concentration of the drug could rise, which raises your risk of dose-dependent side effects.

So, for ER forms of the medication that you only take once or twice per day, a doctor is likely to advise against taking it with alcohol and may recommend taking it on an empty stomach.

When should you take it?

The time you should take diltiazem depends on certain factors. For instance, the timing and intake of IR or ER oral tablets of diltiazem differ for each form.

Generally, since the IR form works more quickly, you need to take it three to four times per day. It’s important to follow your doctor’s instructions on the dosage schedule, including the recommended number of hours to wait between doses.

On the other hand, the long-acting form is typically taken once or twice per day, unlike three or four times a day for the immediate type. You should aim to take it at the same time every day. Taking it before breakfast (and therefore on an empty stomach) may be a good strategy to remember to take it daily.

Another factor is the patient’s diagnosis. Diltiazem is a calcium channel blocker that works by stopping or slowing the influx of calcium ions into muscle cells, which can relax the heart muscles and open up the blood vessels. The mechanism of action for diltiazem makes it useful for various chronic medical conditions.

Doctors typically prescribe diltiazem for the following medical conditions: 

• Hypertension: Diltiazem relaxes the smooth muscles in blood vessels, which, in turn, lowers blood pressure.
• Cardiac arrhythmia: Diltiazem can reduce both the rate and force of heart muscle contraction. This effect can help with arrhythmia, which is where your heart beats with an unusual rhythm.
• Angina: In combination with its effects on your blood vessels, diltiazem can reduce the workload and oxygen demands in the heart, which is beneficial for chest pain caused by angina.

Typically, the timing and dosage recommendations of diltiazem for each of these medical conditions vary.
Consult your doctor to get professional advice and recommendations on how best to take diltiazem.

Side effects

The side effects of diltiazem vary for each person. The following are some of the possible side effects:

• vomiting
• diarrhea
• constipation
• dizziness 
• flushing
• headache
• weakness
• reduced heart rate
• nasal congestion
• cough

Some individuals may develop more severe side effects, such as

• unexplained swelling of the face, eyes, lips, tongue, and other body regions
• difficulty breathing or swallowing
• fainting
• extreme tiredness
• unusual bleeding or bruising
• lack of energy
• frequent or severe chest pain

Contact your doctor for prompt treatment if you experience any of these side effects.

Diltiazem alternatives

If diltiazem isn’t working for you, whether because of the dosing schedule or side effects, a doctor might suggest other options to treat high blood pressure or angina:

• Calcium channel blockers: verapamil (Verelan) or nifedipine (Procardia)
• Angiotensin converting enzyme (ACE) inhibitors: lisinopril (Qbrelis), captopril (Capoten), or enalapril (Vasotec)
• Angiotensin receptor blockers: losartan (Cozaar), valsartan (Diovan), or candesartan (Atacand)
• Beta-blockers: metoprolol (Lopressor) or carvedilol (Coreg)
• Diuretics: hydrochlorothiazide (Microzide)
• Cardiac glycoside: digoxin (Lanoxin)

Summary

Doctors typically prescribe diltiazem to manage different medical conditions, such as high blood pressure, cardiac arrhythmias, and angina. The timing and dosing of diltiazem varies for each condition and depends on its type.

It comes in both IR and ER forms. ER tablets are recommended to be taken more times throughout the day, while ER ones take longer to exert their full effect. You usually don’t need to take it on an empty stomach.

Consuming certain foods or alcohol could affect its absorption rate, which may put you at higher risk of side effects. This is usually the case for ER tablets. A doctor will advise you if they want you to take the medication on an empty stomach.

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