Took diltiazem twice today

I took my 1x day 120 mg time released diltiazem this morning at 7 o' clock and a few minutes ago inadvertently took another.  Anyone have experience with this?  I also take xarelto with dinner and flecainide 50 mg 2 x day for afib.  


Overdose Symptoms

by Penguin - 2023-02-09 18:30:23

No experience of this drug whatsoever personally Flo, but this is the advice I found online if you think you've taken too much and what to look out for.  The website to confirm this information is below:

Advice on website: 

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following: slow, fast, or irregular heartbeat, fainting, difficulty breathing, seizures, dizziness, confusion, nausea, vomiting, increased sweating. 

If I was worried I'd  a) check the patient information leaflet in case it says what you should do if you take too much b) check for the symptoms listed for overdose c) call the helpline or your out of hours doctor / ER for reassurance and advice.

All of the above will be far more reliable than a pacemaker forum !! 

Good luck & I hope that this slip up proves to be non-eventful for you. 



by Flo - 2023-02-09 18:42:56

Thank you Penguin, I will read the insert for diltiazem and check out the website now.  


by Gemita - 2023-02-09 18:53:11

Flo, we have all done it and you should be okay with 240 mg Diltiazem.  I think you would need to take 600 mg of the med to be hitting potential toxic territory.

You might find your blood pressure and heart rate will drop with the extra med, but the pacemaker will correct heart rate, so drink plenty of fluids to help maintain blood pressure and to neutralise the med and to flush it through the system so that it will not be too concentrated in the blood stream.  

Consult a doctor or pharmacist is you feel unwell.  I wouldn’t take Diltiazem when it is next due since it will be too early and you don’t want to build up on the extra dose you have already taken.  I would take the once daily dose at the time you wrongly took the second dose and then slowly move it back to your original time, if that makes sense.  

I am unclear whether you will need the 2nd dose of Flecainide though, since the extra Diltiazem will probably be sufficient to control any high heart rates/blood pressure which is why I would consult a doctor or pharmacist.

But please don't panic.  I was on a calcium channel blocker like Diltiazem + Flecainide and occasionally missed or took an extra dose, without any lasting ill effects.  Stay safe


by Flo - 2023-02-09 19:12:41

Thank you Gemita.  I had decided to skip the flecainide and drink more water and my pharmacy is open 24 hours.  Such good comments and support here.  

Timed Release

by Gemita - 2023-02-09 19:26:14

Flo, don't forget too that your Diltiazem being a timed release medication means that the med will be slowly released into your blood stream, so it shouldn't cause such a spike in any of your symptoms.  I am sure you will be safe, but perhaps you might sleep longer than usual.  Goodnight from the UK xx

Time released

by Flo - 2023-02-10 06:03:53

Thank you again Gemita. I will not take the usual morning diltiazem and like you said above will adjust until back to normal time. Hope you had a good night, mine was ok.

Toxic dose

by PapaMike - 2023-02-10 12:59:09

Gemita is almost correct. 600mg is roughly the dose where cardiac features present, whereas other system features can present from as low as 300mg. Renal failure, acute pancreatitis and rhabdomyolysis being some of the less pleasant. Although in fairness you're generally looking at 2g or above before you're arresting.

We treat a potentially toxic dose as being 5mg of diltiazem per kg of body weight. So unless you weigh 48kg or under you'll likely experience no adverse effects.

Peak concentrations of sustained release tend to be between 5 and 11 hours.


Toxic Dose

by Flo - 2023-02-10 14:08:20

Thank you for the reply PapaMike.  I just squeak by the 48kg.

PapaMike and Flo - Excellent information

by Gemita - 2023-02-10 14:49:01

PapaMike, thank you for your input.  Wish we had had you around last night.   Flo has survived her experience, thankfully, but only just on the values you quoted (5 x 48 = 240 mg diltiazem).  How would you professionally (1) treat a potentially toxic dose of Diltiazem and (2) how should patients best treat a potentially toxic dose of Diltiazem at home while waiting for emergency help?  What about Flecainide?  Can you give us some potentially toxic values for low body weight (48 kg) for Flecainide?  Thank you.

You were lucky Flo.  This is useful information in case they try to increase your dose of Diltiazem in the future when you can have a meaningful discussion with your doctors about your concerns for toxicity with your low body weight.

Higher doses

by Flo - 2023-02-10 20:25:52

Hi Marybird and thank you for the reply.  I am glad the higher dose of diltiazem and metoprolol is keeping afib under control for you.  

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