This information is intended for use by health professionals

1. Name of the medicinal product

Retalzem® 60mg MR Tablets

2. Qualitative and quantitative composition

Each tablet contains 60 mg of the active substance diltiazem hydrochloride

Excipients with known effect

Product contains lactose monohydrate, For full list of excipients see section 6.1

3. Pharmaceutical form

Modified release tablet

4. Clinical particulars
4.1 Therapeutic indications

Prophylaxis and treatment of angina pectoris

4.2 Posology and method of administration


Adults The usual dose is one tablet (60mg) three times daily. However, patient responses may vary and dosage requirements can differ significantly between individual patients. If necessary the dosage may be increased, up to 360mg/day. Higher doses, up to 480mg/day, have been used with benefit in some patients, especially in the treatment of unstable angina. There is no evidence of any decrease in efficacy at these high doses.

Elderly patients or patients with impaired hepatic or renal function

Plasma levels of diltiazem can be increased in these patients. The recommended initial dose is one tablet (60mg) twice daily. Heart rate should be monitored regularly in these patients and the dose should not be increased if the heart rate falls below 50 beats per minute. In patients suffering from liver problems, periodical checks of liver function are recommended during treatment with Retalzem® 60mg MR Tablets.

Paediatric population

Safety and efficacy in children have not been established therefore Retalzem® 60mg MR Tablets is not recommended.

Method of administration

The tablets should be swallowed whole with some water, without crushing or chewing.

4.3 Contraindications

Congestive heart failure, sick sinus syndrome [sinoatrial (SA) and 2nd or 3rd degree atrioventricular (AV) block] in patients without a functioning pacemaker, marked bradycardia (less than 50 beats per minute).

Retalzem® 60mg MR Tables should not be used in pregnancy, in women of child-bearing potential or in mothers who are breast-feeding.

Left ventricular failure with pulmonary stasis.

Hypersensitivity to diltiazem or to any of its excipients.

Retalzem® 60mg MR Tablets like any calcium-channel blocker should not be administered concurrently with dantrolene infusion, because of the risk of ventricular fibrillation (see section 4.5 Interactions with other medicinal products and other forms of interactions).

Combination with ivabradine (see section 4.5).

4.4 Special warnings and precautions for use

Retalzem® 60mg MR Tablets should be used with caution in patients with reduced left ventricular function, bradycardia (because of risk of exacerbation), first degree AV block or prolonged PR interval detected on electrocardiogram (risk of exacerbation and rarely, of complete block).Close observation is necessary in these patients.

In case of surgery with general anaesthesia, the anaesthetist must be informed about current therapy and dosage. Calcium channel blockers may potentiate the depression of cardiac contractility, conductivity and automaticity and vascular dilatation caused by anaesthetics.

The product should be used with caution in elderly patients and in patients with hepatic and renal dysfunction, since plasma diltiazem levels can be increased. The contraindications and precautions should be carefully observed and close monitoring, particularly of heart rate, should be carried out at the beginning of treatment.

Treatment with diltiazem may be associated with mood changes, including depression (see section 4.5 and 4.8). Early recognition of relevant symptoms is important, especially in predisposed patients. In such cases, drug discontinuation should be considered.

Diltiazem has an inhibitory effect on intestinal motility. Therefore it should be used with caution in patients at risk of developing an intestinal obstruction.

Careful monitoring is necessary in patients with latent or manifest diabetes mellitus due to a possible increase in blood glucose.

The use of diltiazem may induce bronchospasm, including asthma aggravation, especially in patients with preexisting bronchial hyper-reactivity. Cases have also been reported after dose increase. Patients should be monitored for signs and symptoms of respiratory impairment during diltiazem therapy.

Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine.

4.5 Interaction with other medicinal products and other forms of interaction

Combinations Contraindicated For Safety Reasons:

Dantrolene (infusion)

Lethal ventricular fibrillation is regularly observed in animals when intravenous verapamil and dantrolene are administered concomitantly. The combination of a calcium antagonist and dantrolene is therefore potentially dangerous (see section 4.3 Contraindications).


Concomitant use with ivabradine is contraindicated due to the additional heart rate lowering effect of diltiazem to ivabradine (see section 4.3 Contraindications).

Combinations Requiring Caution:

In common with other calcium-channel blockers, when Retalzem® 60mg MR Tablets is used with drugs which may induce bradycardia or hypotension or with other antiarrhythmic drugs the possibility of an additive effect should be borne in mind.

Alpha-antagonist agents

Increase of hypotensive effects. Combination of diltiazem with alpha-antagonist drugs may produce or aggravate hypotension; therefore strict monitoring of blood pressure is recommended.


Possible disturbances of conduction (marked bradycardia, sinus node depression, sinus arrest), effects on sinoatrial and atrioventricular conduction and heart failure (synergistic action). Patients receiving such combinations should be regularly monitored by ECG and clinically, especially when initiating the treatment.

Amiodarone, digoxin

Increased risk of bradycardia; caution is required in combination with diltiazem, especially in elderly patients and when high doses are used.

Antiarrhythmic drugs

Since diltiazem has antiarrhythmic activity, concurrent prescription with other antiarrhythmic agents may result in increase of cardiac side effects due to additive effects. Such a combination requires caution and it should be initiated under close ECG and clinical monitoring.

Nitrate derivatives

Should be prescribed at gradually increasing doses due to increase in hypotensive effects and faintness from the additive effects on vasodilation.

In all patients treated with calcium antagonists, the prescription of nitrate derivatives should only be carried out at gradually increasing doses.


Diltiazem causes an increase in circulating ciclosporin levels. It is recommended to decrease the dose, check renal function, titrate blood levels and adjust the dose both during the treatment combination and after its discontinuation.


When co-administered with phenytoin, diltiazem may increase phenytoin plasma concentration. It is recommended that the phenytoin plasma concentrations be monitored.

Antiplatelet drugs

In a pharmacodynamic study, diltiazem was shown to inhibit platelet aggregation. Although the clinical significance of this finding is unknown, potential additive effects when used with antiplatelet drugs should be considered

X-Ray Contrast Media

Cardiovascular effect of an intravenous bolus of an ionic X-ray contrast media, such as hypotension, may be increased in patients treated with diltiazem.

Special caution is required in patients who concomitantly receive diltiazem and X-ray contrast media.


Increase of blood levels of carbamazepine. It is recommended that the plasma concentration of carbamazepine be assayed and that the dose should be adjusted if necessary.


Increase of blood levels of theophylline.

Histamine H2-receptor antagonists (cimetidine or ranitidine)

Increase in plasma levels of diltiazem. Patients currently receiving diltiazem therapy should be carefully monitored when initiating or discontinuing therapy with anti-H2 agents. A change in the diltiazem dose may be necessary.


Plasma levels of diltiazem may be decreased after beginning rifampicin. The patient should be carefully monitored when initiating or discontinuing rifampicin treatment.


Risk of increase in lithium-induced neurotoxicity

Combinations To Be Taken Into Account:

CYP450 3A4

Diltiazem is metabolised by CYP3A4. A moderate (less than 2-fold) increase of diltiazem plasma concentration in cases of co-administration with a stronger CYP3A4 inhibitor has been documented. Grapefruit juice may increase diltiazem exposure (1.2 fold). Patients who consume grapefruit juice should be monitored for increased adverse effects of diltiazem. Grapefruit juice should be avoided if an interaction is suspected. Diltiazem is also a CYP3A4 isoform inhibitor.

Co-administration with other CYP3A4 substrates may result in an increase in plasma concentration of either co-administered drug. Co-administration of diltiazem with a CYP3A4 inducer may result in a decrease of diltiazem plasma concentrations.


Diltiazem is an inhibitor of CYP3A4 and has been shown to significantly increase the AUC of some statins. The risk of myopathy and rhabdomyolysis is increased by concomitant administration of diltiazem with statins metabolised by CYP3A4 (e.g. atorvastatin, fluvastatin and simvastatin). An adjustment to the dose of statin may be necessary (see also product information of the relevant statin). When possible, it is recommended to use a statin not metabolised by CYP3A4 (e.g. pravastatin) with diltiazem.


Inhibition of cilostazol metabolism (CYP3A4). Diltiazem has been shown to increase cilostazol exposure and to enhance its pharmacological activity.

Benzodiazepines (midazolam, triazolam)

Diltiazem significantly increases plasma concentrations of midazolam and triazolam and prolongs their half-life. Special care should be taken when prescribing short-acting benzodiazepines metabolised by the CYP3A4 pathway in patients using diltiazem.

Corticosteroids (methylprednisolone)

Diltiazem can increase methylprednisolone levels (through inhibition of CYP3A4 and possible inhibition of P-glycoprotein). The patient should be monitored when initiating methylprednisolone treatment. An adjustment to the dose of methylprednisolone may be necessary.

General information to be taken into account:

Due to the potential for additive effects, caution and careful titration are necessary in patients receiving diltiazem concomitantly with other agents known to affect cardiac contractility and/or conduction.

4.6 Fertility, pregnancy and lactation


There is very limited data from the use of diltiazem in pregnant patients. Diltiazem hydrochloride is teratogenic (see section 5.3) in certain animal species (rat, mice, rabbit). In the absence of adequate evidence of safety in human pregnancy, Retalzem® 60mg MR Tablets should not be used in pregnancy or in women of child bearing potential. If it is considered essential that diltiazem hydrochloride be given to a woman of child bearing potential, the possibility of pregnancy must be excluded before starting the treatment and adequate contraception must be used throughout the therapy.


Diltiazem hydrochloride is excreted in breast milk, therefore, breast feeding whilst taking diltiazem is contraindicated. If use of Retalzem® 60mg MR Tablets is considered essential, another method of infant feeding should be instituted.

4.7 Effects on ability to drive and use machines

No studies on ability to drive or use machines have been performed. Side effects such as dizziness (common), malaise (common) or syncope can occur, particularly at start of treatment or after changes in dose and patients should ensure they do not have these effects before driving or operating machinery.

4.8 Undesirable effects

The following CIOMS frequency rating is used, when applicable: 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 (cannot be estimated from the available data).

Within each frequency grouping, adverse events are presented in order of decreasing seriousness.

Very common




Not known

Blood and lymphatic system disorders


Psychiatric disorders

Nervousness, insomnia

Mood changes (including depression)

Nervous system disorders

Headache, dizziness

Extrapyramidal syndrome

Respiratory, thoracic and mediastinal disorders

Bronchospasm (including asthma aggravation)

Cardiac disorders

Atrioventricular block (may be of first, second or third degree; bundle branch block may occur), palpitations


Sinoatrial block, congestive heart failure, sinus arrest, cardiac arrest (asystole)

Vascular disorders


Orthostatic hypotension

Vasculitis (including leukocytoclastic vasculitis)

Gastrointestinal disorders

Constipation, dyspepsia, gastric pain, nausea

Vomiting, diarrhea

Dry mouth

Gingival hyperplasia

Metabolism and nutrition disorders


Hepatobiliary disorders

Hepatic enzymes increase (AST, ALT, LDH, ALP increase)


Skin and subcutaneous tissue disorders



Photosensitivity (including lichenoid keratosis at sun exposed skin areas), angioneurotic oedema, rash, erythema multiforme (including Steven-Johnson's syndrome and toxic epidermal necrolysis), sweating, exfoliative dermatitis, acute generalized exanthematous pustulosis, occasionally desquamative erythema with or without fever

Reproductive system and breast disorders


General disorders and administration site conditions

Peripheral oedema


Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorization of the medicinal product is important.It allows continued monitoring of the benefit/risk balance of the medical product Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme Website: or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9 Overdose

The clinical effects of acute overdose can involve pronounced hypotension leading to collapse, sinus bradycardia with or without isorhythmic dissociation, sinus arrest, atrioventricular conduction disturbances and cardiac arrest.

Treatment, under hospital supervision, will include gastric lavage, osmotic diuresis. Conduction disturbances may be managed by temporary cardiac pacing.

Proposed corrective treatments: atropine, vasopressors, inotropic agents, glucagon and calcium gluconate infusion.

5. Pharmacological properties
5.1 Pharmacodynamic properties

Pharmacotherapeutic group: Calcium channel blockers; Benzothiazepine derivatives, ATC code: C08DB01

Diltiazem is a benzothiazepine calcium-channel blocking agent. These agents interfere with the influx of calcium ions through the slow channels of active cell membranes, influencing the myocardial cells, the cells within the specialised conducting system of the heart and the cells of vascular smooth muscle. It is used in the management of classical and vasospastic angina pectoris. The efficacy of diltiazem in the treatment of angina pectoris is probably related to its coronary vasodilating properties (causing an increase in myocardial oxygen supply) and to some of its haemodynamic effects (resulting in a decrease in myocardial work/oxygen demand).

Although diltiazem is a potent vasodilator, the reduction in blood pressure that often accompanies its use usually occurs without reflex tachycardia, as diltiazem has little effect on the peripheral vasculature.

Diltiazem causes a small reduction in heart rate which is accompanied by an increase in cardiac output, improved myocardial perfusion and reduction of ventricular work. In animal studies diltiazem protects the myocardium against the effects of ischaemia and reduces the damage produced by excessive entry of calcium in to the myocardial cell during perfusion.

Diltiazem has a less negative inotropic effect than verapamil and significant myocardial depression rarely occurs.

5.2 Pharmacokinetic properties

Diltiazem hydrochloride is effective in angina, protecting the heart against ischaemia,

vasodilating coronary arteries and reducing myocardial oxygen requirements. It is well tolerated and does not generally give rise to side effects associated with peripheral vasodilators, nor cause significant myocardial depression.


Diltiazem is rapidly and almost completely (about 90%) absorbed from the gastro-intestinal tract after oral administration. However, it is subject to extensive first-pass hepatic metabolism, reported to reduce the bioavailability to about 40%. The absolute bioavailability is dose related. Peak plasma concentration is reached within about 3 to 4 hours after oral dosing and steady-state plasma concentrations are reached in about 3 days.


The mean volume of distribution is about 5L/kg. Diltiazem is highly lipophilic and appears in cerebrospinal fluid (rabbit studies) and in breast milk. It is highly protein bound (80- 90%), as is its most active metabolite, desacetyl diltiazem (60-75%).


Diltiazem is extensively metabolized by the liver. Diltiazem is 80 to 85% bound to plasma proteins. The most important metabolites being N-mono-desmethyl diltiazem (with 20% of potency of diltiazem), desacetyl diltiazem (50% relative potency) and N- demethyl desacetyl diltiazem. The metabolites are detectable in plasma within 30 minutes, reaching concentrations of 30-50%, 10-30% and 10-20% of the parent drug, respectively.


The elimination half-life of oral diltiazem is about 4-8 hours and it is longer for the metabolites. Excretion of diltiazem and its metabolites is mainly in the urine. Less than 5% of a dose of diltiazem is excreted in the urine as unchanged drug within 24 hours.

Linearity/ non-linearity

There is a linear relationship between dose and plasma concentration. During long- term administration to any one patient, plasma concentrations of diltiazem remain constant.

Mean plasma concentrations in elderly subjects and patients with renal and hepatic insufficiency are higher than in young subjects.

Diltiazem and its metabolites are poorly dialysed

5.3 Preclinical safety data

Pregnancy: Reproduction studies have been conducted in mice, rats and rabbits. Administration of doses ranging from 4 to 6 times (depending on species) the upper limit of the optimum dosage range in clinical trials (480mg q.d. or 8mg/kg q.d. for a 60kg patient) resulted in embryo and fetal lethality. These studies revealed, in one species or another, a propensity to cause fetal abnormalities of the skeleton, heart, retina, and tongue. Also observed were reductions in early individual pup weights, pup survival, as well as prolonged delivery times and an increased incidence of stillbirths. Diltiazem has been shown to be teratogenic in some animal species and it is therefore contra- indicated in pregnancy and in women of child-bearing potential.

Diltiazem is freely diffusible in breast milk. It should not be given to nursing mothers until more information becomes available concerning safety in infants.

6. Pharmaceutical particulars
6.1 List of excipients

Lactose Monohydrate

Hydrogenated castor oil

Macrogol 6000

Magnesium stearate

6.2 Incompatibilities

None known.

6.3 Shelf life

For product as packaged for sale: 3 years.

6.4 Special precautions for storage

Do not store above 25°C. Store in original package in order to protect from moisture

6.5 Nature and contents of container

Strip (heat-sealed PVC/aluminium foil blister) of 25 tablets.

50 tablets (2 strips) or 100 tablets (4 strips) in an outer cardboard carton.

6.6 Special precautions for disposal and other handling

The tablets should be swallowed whole with water, without crushing or chewing.

Administrative Data

7. Marketing authorisation holder

Athlone Pharmaceuticals


Co. Roscommon,


8. Marketing authorisation number(s)


9. Date of first authorisation/renewal of the authorisation


10. Date of revision of the text