What are the side effects of Diltiazem (generic name for Cardizem, a calcium channel blocker)?

From the Guidelines

Diltiazem commonly causes side effects including hypotension, dizziness, flushing, bradycardia, and edema. Patients may also experience nausea, headache, and peripheral edema. More serious but less common side effects include irregular heartbeat, shortness of breath, fainting, and allergic reactions. Diltiazem works by blocking calcium channels in the heart and blood vessels, which relaxes blood vessels and reduces heart workload, but this mechanism also explains many of its side effects. For example, the vasodilation effect can cause dizziness and headaches, while the slowing of heart conduction can lead to bradycardia in some patients 1.

Side Effects of Diltiazem

• Hypotension
• Dizziness
• Flushing
• Bradycardia
• Edema
• Nausea
• Headache
• Peripheral edema

According to the most recent evidence, diltiazem and verapamil should not be used in combination with ivabradine due to the risk of severe bradycardia 1. The major adverse effects of diltiazem are systemic hypotension, headache, dizziness, flushing, palpitations, and leg edema. Owing to its intrinsic negative inotropic effects, diltiazem might also reduce left ventricular contractility.

Important Considerations

• Diltiazem can have a detrimental effect on mortality rates in patients with LV dysfunction 1
• Verapamil and diltiazem should be avoided in patients with pulmonary edema or evidence of severe LV dysfunction 1
• Regular monitoring by a healthcare provider is important while taking this medication
• Patients should not stop taking diltiazem suddenly without medical supervision as this could worsen underlying conditions 1

From the FDA Drug Label

ADVERSE REACTIONS Serious adverse reactions have been rare in studies carried out to date, but it should be recognized that patients with impaired ventricular function and cardiac conduction abnormalities usually have been excluded In domestic placebo-controlled angina trials, the incidence of adverse reactions reported during diltiazem hydrochloride therapy was not greater than that reported during placebo therapy. The following represent occurrences observed in clinical studies of angina patients. In many cases, the relationship to diltiazem hydrochloride has not been established The most common occurrences from these studies, as well as their frequency of presentation, are edema (2.4%), headache (2.1%), nausea (1.9%), dizziness (1.5%), rash (1.3%), and asthenia (1. 2%) In addition, the following events were reported infrequently (less than 1%): Cardiovascular: Angina, arrhythmia, AV block (first-degree), AV block (second- or third-degree – see WARNINGS, Cardiac Conduction), bradycardia, bundle branch block, congestive heart failure, ECG abnormality, flushing, hypotension, palpitations, syncope, tachycardia, ventricular extrasystoles Nervous System: Abnormal dreams, amnesia, depression, gait abnormality, hallucinations, insomnia, nervousness, paresthesia, personality change, somnolence, tremor Gastrointestinal: Anorexia, constipation, diarrhea, dysgeusia, dyspepsia, mild elevations of alkaline phosphatase, SGOT, SGPT, and LDH (see WARNINGS, Acute Hepatic Injury), thirst, vomiting, weight increase elevation, dry mouth, dyspnea, epistaxis, eye irritation, hyperglycemia, hyperuricemia, impotence, muscle cramps, nasal congestion, nocturia, osteoarticular pain, polyuria, sexual difficulties, tinnitus The following postmarketing events have been reported infrequently in patients receiving diltiazem hydrochloride tablets: acute generalized exanthematous pustulosis, allergic reactions, alopecia, angioedema (including facial or periorbital edema), asystole, erythema multiforme (including Stevens-Johnson syndrome, toxic epidermal necrolysis), extrapyramidal symptoms, gingival hyperplasia, hemolytic anemia, increased bleeding time, leukopenia, photosensitivity (including lichenoid keratosis and hyperpigmentation at sun-exposed skin areas), purpura, retinopathy, myopathy, and thrombocytopenia There have been observed cases of a generalized rash, some characterized as leukocytoclastic vasculitis. In addition, events such as myocardial infarction have been observed, which are not readily distinguishable from the natural history of the disease in these patients. A definitive cause and effect relationship between these events and diltiazem hydrochloride therapy cannot yet be established Exfoliative dermatitis (proven by rechallenge) has also been reported.

The common side effects of Diltiazem include:

• Edema (2.4%)
• Headache (2.1%)
• Nausea (1.9%)
• Dizziness (1.5%)
• Rash (1.3%)
• Asthenia (1.2%) The less common side effects include:
• Cardiovascular events such as angina, arrhythmia, and congestive heart failure
• Nervous system events such as abnormal dreams, depression, and hallucinations
• Gastrointestinal events such as anorexia, constipation, and diarrhea
• Other events such as allergic reactions, alopecia, and photosensitivity 2

From the Research

Diltiazem Side Effects

• The most common side effects of diltiazem include headache due to peripheral vasodilatation and depression of atrioventricular nodal conduction 3
• These side effects occur in only 2 to 10% of patients receiving diltiazem and are generally minor in nature 3
• Other possible side effects of diltiazem include:
  • Vasodilatory symptoms such as dizziness, headaches, flushing sensation, and palpitation 4
  • Negative inotropic effects, which can lead to decreased cardiac contractility 4
  • Conduction disturbances, such as bradycardia and sinus arrest 4, 5
  • Gastrointestinal effects, such as nausea and constipation 4, 6
• Diltiazem can also interact with other medications, such as beta-adrenergic blocking drugs, to increase the risk of profound bradycardia and hypotension 5
• Idiosyncratic side effects, such as urticarial rashes, gingival hyperplasia, arthralgia, hepatotoxicity, and transient mental confusion or akathisia, have also been reported 6