Is my dad’s dizziness due to the Ivabradine dose?

Question

Hello, Doctor,

My dad just had an acute heart attack (myocardial infarction) and had subsequent coronary angioplasty with one stent placed in the LAD artery. His ejection fraction (EF) is approximately 26%. He also recently started treatment for Type 2 diabetes (HbA1c 13.7%) and is currently on insulin and oral diabetes medications.

The discharge prescription states he should take Ivabradine 2.5 mg twice daily. However, the pharmacy dispensed Ivabradine 5 mg tablets, and we mistakenly gave him one full 5 mg tablet in the morning and one full 5 mg tablet at night (total 10 mg/day) over the last 6 days, thinking it was the prescribed dose.

We saw today that the prescription actually says 2.5 mg BD. Now, his pulse rate is about 65 beats/minute. His blood pressure commonly stays around 100/68 mmHg (sometimes 95/65, then about 100/68 on repeat). He is not unconscious and has no severe dizziness. Sometimes when he sleeps, he will have a short period of rapid breathing and then normal. Is this episode related to the higher ivabradine dose or more likely related to his recent MI and low EF?

My questions are:

Can Ivabradine 10 mg cause any harm?
Do we hold the medicine temporarily or continue at the correct prescribed dose?
The tablets are 5 mg and are not scored. Do we split them or get a different strength?
Does he need an ECG or any other work-up in the setting of this dosing error?
Are there any signs that would require immediate medical attention?

Kindly advise.

Thank you.

Answer 1

Hello,

Welcome to icliniq.com.

I read your query and can understand your concern.

Sorry your family is going through this, and it is very understandable how this mix-up happened after such a stressful hospitalization. The reassuring news is that your father has been taking a total of 10 mg of Ivabradine (hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker) a day for 6 days, which is still within the normal therapeutic dosing range for many adults, although it is more than the dose his cardiologist intended.

A pulse in the mid-60s, blood pressure in the low 100s over the upper 60s, and no fainting or major dizziness. It does not seem likely that this dosing error has resulted in any major damage. The episodes of rapid breathing during sleep are more likely related to the following factors:

Heart attack.
Reduced ejection fraction can be associated with heart failure.
Sleep-disordered breathing, rather than Ivabradine itself.

He should not stop the medication suddenly, unless his cardiologist specifically instructs him to do so. Instead, call his cardiologist or treating physician as soon as possible and tell them about the dosing error and ask if he should now be on the prescribed 2.5 mg twice daily. Not all 5 mg tablets are designed to be split accurately, so it is usually better to get the correct 2.5 mg tablets if available or check with the pharmacist whether the particular 5 mg tablet can be safely split.

An ECG is not necessary if he stays well, but it is prudent for his doctor to do one, especially given his previous myocardial infarction and low ejection fraction. They might also like to check his heart rate and blood pressure. If he develops a very slow pulse, fainting, severe dizziness, chest pain, worsening shortness of breath, confusion, or palpitations, or if his breathing becomes persistently difficult (rather than only for a brief period of time during sleep), seek immediate medical attention.

He has recently had a heart attack, has a low ejection fraction, and has been newly diagnosed with diabetes with a very high HbA1c, so close follow-up with his cardiologist and diabetes team is very important to optimize his recovery and reduce the risk of future complications.

I hope this information helps you.

Feel free to ask further questions.

Thank you.