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Tiazac Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 11/14/2016

Tiazac (diltiazem hydrochloride) is a calcium channel blocker used to treat hypertension (high blood pressure), angina (chest pain), and certain heart rhythm disorders. Tiazac is available in generic form. Common side effects of Tiazac include:

Tell your doctor if you have unlikely but serious side effects of Tiazac including:

  • fainting,
  • slow/irregular/pounding/fast heartbeat,
  • swelling ankles or feet,
  • shortness of breath,
  • unusual tiredness,
  • unexplained or sudden weight gain,
  • mental/mood changes (such as depression, agitation), or
  • unusual dreams.

Doasge of Tiazac depends on the individual, their response to the medication and the condition being treated. Usual starting doses are 120 to 240 mg once daily. Tiazac may interact with amiodarone, buspirone, carbamazepine, cimetidine, cyclosporine, digoxin, lovastatin, rifampin, quinidine, sedatives, antibiotics, antifungals, beta-blockers, or HIV/AIDS medicines. Tell your doctor all medications you are taking. Tiazac should be used only when prescribed during pregnancy. This drug passes into breast milk and may have undesirable effects on a nursing infant. Consult your doctor before breastfeeding.

Our Tiazac (diltiazem hydrochloride) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Tiazac in Detail - Patient Information: Side Effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • a red, blistering skin rash;
  • swelling in your hands or feet;
  • trouble breathing;
  • slow heartbeats;
  • dizziness, fainting, fast or pounding heartbeat;
  • upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • severe skin reaction -- fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Less serious side effects may include:

  • headache;
  • dizziness, weakness, tired feeling;
  • upset stomach, nausea;
  • sore throat, cough, stuffy nose; or
  • flushing (warmth, redness, or tingly feeling).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Tiazac (Diltiazem Hcl)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Tiazac Overview - Patient Information: Side Effects

SIDE EFFECTS: Dizziness, lightheadedness, weakness, nausea, flushing, constipation, and headache may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To lower the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: fainting, slow/irregular/pounding/fast heartbeat, swelling ankles/feet, shortness of breath, unusual tiredness, unexplained/sudden weight gain, mental/mood changes (such as depression, agitation), unusual dreams.

Tell your doctor immediately if any of these rare but very serious side effects occur: severe stomach/abdominal pain, dark urine, persistent nausea/vomiting, yellowing eyes/skin.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Tiazac (Diltiazem Hcl)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Tiazac FDA Prescribing Information: Side Effects
(Adverse Reactions)


Serious adverse reactions have been rare in studies with Tiazac, as well as with other diltiazem formulations. It should be recognized that patients with impaired ventricular function and cardiac conduction abnormalities have usually been excluded from these studies. A total of 256 hypertensives were treated for between 4 and 8 weeks; a total of 207 patients with chronic stable angina were treated for 3 weeks with doses of Tiazac ranging from 120 to 540 mg once daily. Two patients experienced first-degree AV block at the 540 mg dose. The following table presents the most common adverse reactions, whether or not drug-related, reported in placebo-controlled trials in patients receiving Tiazac up to 360 mg and up to 540 mg with rates in placebo patients shown for comparison.


Adverse Events (COSTART Term) Placebo Tiazac
# pts (%)
Up to 360 mg
# pts (%)
480 - 540 mg
# pts (%)
edema, peripheral 1 (2) 8 (5) 7 (15)
dizziness 4 (7) 6 (4) 2 (4)
vasodilation 1 (2) 5 (3) 1 (2)
dyspepsia 0 (0) 7 (5) 0 (0)
pharyngitis 2 (4) 3 (2) 3 (6)
rash 0 (0) 3 (2) 0 (0)
infection 2 (4) 2 (1) 3 (6)
diarrhea 0 (0) 2 (1) 1 (2)
palpitations 0 (0) 2 (1) 1 (2)
nervousness 0 (0) 3 (2) 0 (0)


Adverse Events (COSTART Term) Placebo Tiazac
# pts (%)
Up to 360 mg
# pts (%)
540 mg
# pts (%)
headache 1 (2) 13 (8) 4 (8)
edema, peripheral 1 (2) 3 (2) 5 (10)
pain 1 (2) 10 (6) 3 (6)
dizziness 0 (0) 5 (3) 5 (10)
asthenia 0 (0) 1 (1) 2 (4)
dyspepsia 0 (0) 2 (1) 3 (6)
dyspnea 0 (0) 1 (1) 3 (6)
bronchitis 0 (0) 1 (1) 2 (4)
AV block 0 (0) 0 (0) 2 (4)
infection 0 (0) 2 (1) 1 (2)
flu syndrome 0 (0) 0 (0) 1 (2)
cough increase 0 (0) 2 (1) 1 (2)
extrasystoles 0 (0) 0 (0) 1 (2)
gout 0 (0) 2 (1) 1 (2)
myalgia 0 (0) 0 (0) 1 (2)
impotence 0 (0) 0 (0) 1 (2)
conjunctivitis 0 (0) 0 (0) 1 (2)
rash 0 (0) 2 (1) 1 (2)
abdominal enlargement 0 (0) 0 (0) 1 (2)
* Adverse events occurring in treated patients at 2% or more than placebo-treated patients.

In addition, the following events have been reported infrequently (less than 2%) in clinical trials with other diltiazem products:

Cardiovascular: Angina, arrhythmia, AV block (second- or third-degree), bundle branch block, congestive heart failure, ECG abnormalities, hypotension, palpitations, syncope, tachycardia, ventricular extrasystoles.

Nervous System: Abnormal dreams, amnesia, depression, gait abnormality, hallucinations, insomnia, nervousness, paresthesia, personality change, somnolence, tinnitus, tremor.

Gastrointestinal: Anorexia, constipation, diarrhea, dry mouth, dysgeusia, mild elevations of SGOT, SGPT, LDH, and alkaline phosphatase (see WARNINGS, Acute Hepatic Injury), nausea, thirst, vomiting, weight increase.

Dermatological: Petechiae, photosensitivity, pruritus.

Other: Albuminuria, allergic reaction, amblyopia, asthenia, CPK increase, crystalluria, dyspnea, edema, epistaxis, eye irritation, headache, hyperglycemia, hyperuricemia, impotence, muscle cramps, nasal congestion, neck rigidity, nocturia, osteoarticular pain, pain, polyuria, rhinitis, sexual difficulties, gynecomastia.

In addition, the following postmarketing events have been reported infrequently in patients receiving diltiazem hydrochloride: acute generalized exanthematous pustulosis, alopecia, erythema multiforme, exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, extrapyramidal symptoms, gingival hyperplasia, hemolytic anemia, increased bleeding time, photosensitivity (including lichenoid keratosis and hyperpigmentation at sun-exposed skin areas), leukopenia, purpura, retinopathy, and thrombocytopenia. 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 number of well-documented cases of generalized rash, characterized as leukocytoclastic vasculitis, have been reported. However, a definitive cause and effect relationship between these events and diltiazem hydrochloride therapy is yet to be established.

Read the entire FDA prescribing information for Tiazac (Diltiazem Hcl)

Tiazac - User Reviews

Tiazac User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Tiazac sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


Get tips on handling your hypertension.