Brief Answer:
I would explain as follows:

Detailed Answer:
Hello!

Welcome on HCM!

I passed carefully through your concern and would like to explain that it is necessary a frequent and careful medical monitoring of ECG (for possible QTc interval prolongation), possible bradycardia, and renal function during Tikosyn treatment as the risk for adverse effects is always present.

So, on my opinion it is necessary that you contact again with your doctor and discuss on the possibility of checking again a new test for your renal function, heart rate and ECG parameters (especially QTc interval duration).

All the above consideration is due to the potential of Tikosyn for inducing dangerous and life-threatening arrhythmias like torsades de pointes.

In addition, blood electrolytes level (especially potassium and magnesium) should be checked repeatedly for assuring they are within normal ranges and do not contribute in triggering such adverse effects.

There are also several drugs that may interfere with Tikosyn and by decreasing its metabolism risk to increase Tikosyn blood level and contribute such way in a higher adverse effects frequency.

Diltiazem (cardizem) is well known in increase Tikosyn blood level by competing in tubular clearance process.

Also, special foods may increase Tikosyn blood levels such as grapefruit juice.

So, the most rational approach would be to avoid such combination (Tikosyn and Cardizem) especially when additional active drugs are being used (in your case Coreg). And when such a combination (Tikosyn and Cardizem) is inevitable special monitoring is necessary every 2-3 months as I explained above (ECG, heart rate, blood electrolytes level, renal function tests).

As you are experiencing headache, dizziness, palpitations an immediate medical checkup is necessary first to clarify whether a new episode of afib has appeared and second to investigate for a possible occurrence of adverse effects due to the combination Tikosyn and Cardizem.

Tikosyn may display also adverse effects such as headache in up to 11% of cases, dizziness in up to 8% of cases; Amlodipine may be associated with these similar unpleasant manifestations to a much lower frequency. And when these two drugs are taken concomitantly the level of these adverse effects is expected to be higher.

Meanwhile a combination of Cardizem and Amlodipine is not recommended due to the potential for increased adverse effects.

In conclusion, I think that your action to stop Cardizem temporarily until to clarify this issue with your prescribing doctor is the best way of dealing with your recent symptomatology.

I believe that Tikosyn and Coreg are acceptable as a maintenance therapy.

You just need to insist and talk again to your doctor.

That's my personal professional opinion.

Hope to have been helpful to you!

In case of any further uncertainties, feel free to ask me again.

Kind regards,

Dr. Iliri

---