I am facing anorgasmia and difficulty in erection after taking Primidone for tremors. Why?

Question

Hi doctor,

I am a 28-year-old male who suffers from an essential tremor on upper limbs (hands, limb, and voice). My neurologist put me on Primidone (Mysoline) 125 mg every morning and 125 mg every night at bedtime. My tremor has improved, almost disappeared, but I have no more libido. I also have difficulties with erections and anorgasmia (even during masturbation). I cannot take Propranolol because I have allergic asthma, so nonselective beta-blockers are contraindicated. I cannot take Gabapentin or Pregabalin because they caused respiratory depression during the night (I have sleep apnea). Could Primidone (and its metabolite Phenobarbital) cause such sexual dysfunction? I know some antiepileptic drugs can induce CYP450, and specifically, Primidone and its active metabolite are inducers of CYP3A4, and there are interferences with aromatase reaction involves testosterone. I had a sexual hormones blood check done last month.

1) TSH is 4.56 mlU/L.

2) Prolactin is 44.01 ng/mL.

3) Testosterone is 4.8 ng/mL.

4) SHBG is 13 nmol/L

If Primidone could cause these side effects, can I switch to another medication? If so, how should I do the titration of the new medication (and the withdrawal of Primidone)? And, if not, what could be done to treat my sexual dysfunction? Kindly help me.

Answer 1

Hi,

Welcome to icliniq.com.

Sorry to hear about this problem of yours. You are pretty well informed about your problems and the drugs that you are on. So for young people like you, who have problems with erection and orgasm, especially after Primidone, I would advise gradually taper the drug to half for the next five days and then stop in another ten days. Selective beta-blockers like Atenolol are also effective in controlling tremors. I suggest you start with Atenolol 25 mg and then gradually take it up to 75 or a maximum of 100 with careful monitoring of blood pressure. Another option would be to moderate the dose of Clonazepam starting from 0.25 mg and gradually to double and going until 1 to 2 mg, although higher doses have been given. Lorazepam is another good option. If you are not willing to change the Primidone, then you can add Sildenafil (Viagra) for the ED (erection dysfunction). I hope this helps you. Please let me know if I can help you further.