Adverse reactions : תופעות לוואי

4.8 Undesirable effects

The most frequently reported undesirable effects are dizziness and visual disturbances, which occur in around 15% of patients. These effects usually disappear after a few days in the further course of the therapy, or can be resolved by reducing the dose.

The evaluation of undesirable effects is based on the following frequencies: 
Very common:             ≥ 1/10
Common:                  ≥ 1/100 to <1/10
Uncommon:                ≥ 1/1 000 to <1/100
Rare:                    ≥ 1/10 000 to <1/1 000
Very rare:               <1/10 000
Not known:              (Frequency cannot be estimated from the available data) 

Blood and lymphatic system disorders:
Uncommon:               Leukocytopenia, thrombocytopenia, reduced red blood cell count.
These changes are usually mild.
Immune system disorders:
Very rare:            Increase in anti-nuclear antibodies with or without systemic inflammation

Psychiatric disorders:
Common:                  Depression, anxiety, insomnia
Uncommon:                Confusion, amnesia, hallucinations

Nervous system disorders:
Very common:           Dizziness (balance disorders), usually temporary Common:                Headache, paraesthesia, hypoaesthesia, ataxia, syncope, flushing, increased sweating, tremor
Uncommon:              Dyskinesia, muscle twitching, peripheral neuropathy, cramps Rare:                  Drowsiness

Eye disorders:
Very common:             Vision disorders, e.g. double vision, colour halos around light sources, blurry vision
Very rare:               Corneal deposits

Diseases of the ear and labyrinth:
Common:                  Tinnitus
Rare:                    Vertigo

Cardiac disorders:
Common:                  Proarrhythmic effects (most likely in patients with structural heart disease and/or significant left heart failure, see section 4.3
“Contraindications”).
As a class I antiarrhythmic, flecainide may cause proarrhythmic effects, trigger new arrhythmias or change the frequency or severity of an existing arrhythmia. This can severely impair cardiac function, possibly resulting in cardiac arrest. Especially at higher doses of flecainide, there is the possibility of an increase in arrhythmias or heart rate.
Both ventricular arrhythmias and ventricular tachycardia have been reported, e.g. an increase in ventricular extrasystoles, increased frequency of premature ventricular contractions, increased frequency and severity of ventricular tachycardia, ventricular fibrillation.
Patients with atrial flutter receiving flecainide have developed 1:1 AV conduction after an initial slowing of atrial activity and subsequent acceleration of ventricular activity.
Conduction disorders may worsen under treatment with flecainide.
AV blocks (second- and third- degree), bundle branch block or SA block have been observed. Treatment with flecainide should be stopped in such cases.
Bradycardia or sinus arrest can occur.


Treatment with flecainide can cause heart failure. Previously undetected heart failure (latent heart failure, NYHA I) may worsen under treatment with flecainide (clinical manifestation). In this case, a dose reduction or compensation through co-administration of medications to increase cardiac output is required (see section 4.2).


Not known:               Cardiac arrest, chest pain, hypotension, myocardial infarction, palpitations, atrial tachycardia and unmasking of pre-existing
Brugada syndrome can occur.
Dose-dependent prolongation of the PR and QRS intervals and a change in pacing threshold can occur (see section 4.4).

Respiratory, thoracic and mediastinal disorders:
Common:                  Respiratory distress
Uncommon:                Interstitial pneumonitis
Not known:               Pulmonary fibrosis, interstitial lung disease 
Gastrointestinal disorders:
Common:                  Nausea, vomiting, diarrhoea, digestive disturbance, constipation Uncommon:                Dry mouth, taste disorders, abdominal pain, loss of appetite, flatulence

Hepatobiliary disorders:
Rare:                    Elevated liver enzyme levels, with or without jaundice Not known:               Hepatic dysfunction

Skin and subcutaneous tissue disorders:
Common:                Rash
Uncommon:              Allergic skin reactions, alopecia
Rare:                  Severe urticaria
Very rare:             Photosensitivity

Musculoskeletal and connective tissue disorders:
Uncommon:              Arthralgia, myalgia (possibly with fever)
Reproductive system and breast disorders:
Uncommon:             Impotence

General disorders and administration site problems:
Common:                Weakness, fatigue, fever, oedema

Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.
Any suspected adverse events should be reported to the Ministry of Health according to the National Regulation by using an online form https://sideeffects.health.gov.il/