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DOXAZOSIN TABLETS 4MG
Active substance(s): DOXAZOSIN MESILATE / DOXAZOSIN MESILATE / DOXAZOSIN MESILATE
NAME OF THE MEDICINAL PRODUCT
Doxazosin Tablets 4mg
QUALITATIVE AND QUANTITATIVE COMPOSITION 1 tablet Doxazosin Tablets 4 mg contains 4.85 mg of doxazosin Mesylate (equivalent to 4 mg of doxazosin)
PHARMACEUTICAL FORM Tablets
CLINICAL PARTICULARS Therapeutic indications Doxazosin Tablets 4 mg is indicated for the treatment of essential hypertension.
Posology and method of administration Unless prescribed otherwise, the following dosage regimen is recommended: Start therapy with 1 mg of doxazosin once daily. Depending on the individual patients blood pressure response, dosage may, after 1 2 weeks, be increased to 2 mg of doxazosin once daily, if necessary, then to 4 mg of doxazosin once daily, and eventually to 8 mg of doxazosin daily. Average daily dose for maintenance therapy: 2 4 mg of doxazosin once daily. Maximum dose: 16 mg of doxazosin.
Use in the elderly people and in patients with renal insufficiency
As the pharmacokinetics of doxazosin are unchanged in the elderly and in patients with renal insufficiency, such patients can be treated with the usual dose.
Use in patients with hepatic insufficiency
Particular caution should be exercised when determining the dosage in patients with hepatic insufficiency. Clinical data are lacking for patients with serious hepatic dysfunction (see 4.4 Special warnings and special precautions for use). Doxazosin tablets 4 mg can be used as monotherapy or in combination with a thiazide diuretic or beta-blocking agent when treatment with these alone has not given the desired effect or is unsuitable. The tablets should be taken with sufficient fluid in the morning. The attending doctor will decide upon the duration of treatment.
Contraindications Doxazosin Tablets 4 mg is contra-indicated in patients with a known hypersensitivity to the active substance doxazosin or to other quinazolines (e. g. Prazosin, Terazosin) or to any of the other constituents. Doxazosin Tablets 4 mg is contraindicated during lactation, see section 4.6.
Special warnings and special precautions for use During the onset of therapy, circulatory disorders can occur with a tendency to postural hypotension (orthostatic dysregulation). To minimise the risk of postural hypotension, patients should be kept under observation at the beginning of therapy. The risk of such an occurrence is greater if the recommended initial dose is exceeded. The dosage guidelines should therefore be strictly adhered to. Patients on sodium-low diet or treated with diuretics seem more sensitive for the potential for postural effects. Because of its vasodilator effect, doxazosin should be administered with caution in the following cardiac emergencies: pulmonary oedema caused by aortic or mistral stenosis high output cardiac insufficiency right ventricular heart failure caused by pulmonary embolism or pericardial effusion left ventricular heart failure with low filling pressure
In patients with serious coronary suffering, a too quick or too distinct lowering of the blood pressure can result in worsening of anginal complaints.
Use in patients with hepatic insufficiency
Doxazosin should be used with particular caution in patients with impaired hepatic function. As clinical data are lacking for patients with severe hepatic dysfunction, use is not recommended for these patients.
Use in children
Due to the lack of relevant experience, Doxazosin Tablets 4 mg cannot be recommended for use in children.
Interaction with other medicinal products and other forms of interaction Doxazosin Tablets 4 mg increases the blood pressure lowering effect of other antihypertensive drugs. The antihypertensive effect may be increased when doxazosin is administered concomitantly with vasodilators and nitrates. As for other antihypertensive agents, non-steroidal antirheumatics or estrogens may reduce the antihypertensive effect of doxazosin. Sympathomimetics may reduce the anthypertensive effect of doxazosin; doxazosin may reduce blood pressure and vascular reactions to dopamine, ephedrine, epinephrine, metaramizol, methoxamine and phenylephrine. There are no studies concerning interactions with agents influencing hepatic metabolism (ew. g. cimetidine). Doxazosin may increase plasma renin activity and urinary excretion of vanillylmandelic acid. This should be considered when interpreting laboratory data. Pregnancy and lactation As there are no adequate and well-controlled studies in pregnant women and nursing mothers, safe use of Doxazosin tablets 4 mg during pregnancy and lactation has not been established. Although animal studies have produced no evidence of a teratogenic effect, doses approximately 300 times the maximum recommended human therapeutic dose were associated with reduced foetal survival in animals. Doxazosin Tablets 4 mg should therefore be used in pregnant women only after the doctor has carefully weighed expected benefits against potential risks. Animal studies have shown that doxazosin accumulates in breast milk. Consequently, as the safety of doxazosin during lactation has not been established, Doxazosin Tablets 4 mg is contra-indicated in nursing mothers.
Effects on ability to drive and use machines
Treatment of hypertension with Doxazosin Tablets 4 mg must be subject to regular medical supervision. Due to reactions which vary between individuals, responsiveness can be so altered that the ability to drive, to operate machinery or work without a firm hold is compromised. This effect is particularly increased at the beginning of treatment, after a dose increase or a change of medication and in combination with alcohol.
Undesirable effects Side-effects arise mainly from the pharmacological properties of the preparation. Most of the side-effects have been transient or have been tolerated on continued treatment. Common General: Tiredness / nausea, asthenia, headache, chest pain, somnolence. Cardiovascular: Dizziness, postural dizziness, giddiness, oedema, palpitations. CNS: Muscle cramps GI: Constipation, dyspepsia Respiratory: Shortness of breath, nasal congestion. Psych: Delayed ejaculation, apathy Urogenital: Frequent need to urinate, increased urination Eyes: Accommodation disturbances Less common General: Facial / general oedema, syncope, facial redness, fever / shivering, paleness. Cardiovascular: Postural hypotention, arrhythmia, peripheral ischemia, angina pectoris, tachycardia, myocardial infarction. CNS: Tremor, muscle stiffness. GI: Anorexia, increase appetite. Skin: Alopecia. Respiratory: Epistaxis, bronchospasm, cough, pharyngitis. Metabolism: Thirst, hypokalaemia, gout. Musculoskel: Muscle pains, joint swelling / aches, muscle weakness. Psych: Nightmares, memory loss, emotional lability. Urogenital: Incontinence, urinary disturbances, dysuria. Eyes: Abnormal tear flow, photophobia. Ears: Tinnitus. Miscellaneous: Disturbed sense of taste. Rare Cardiovascular: Cerebrovascular distrubances. CNS: depression, agitation, paresthesia. Respiratory passages: Laryngeal oedema. Skin: Rash, itching, purpura. GI: Stomach pains, diarrhoea, vomiting. Liver: Icterus, increased liver enzymes. Metabolism: Hypoglycaemia.
Eyes: blurred vision. Miscellaneous: Impotence, priapism, dysgeusia, decreased body temperature in elderly. Single cases increase of BUN and creatinine, decrease of erythrocytes, leukocytes and thrombocytes. Postural hypotension and, in rare cases, syncope can occur initially during treatment, especially at too high doses, but can also if therapy is restarted after a short break.
Overdose Overdose of Doxazosin Tablets 4 mg generally leads to hypotension, sometimes accompanied by syncope. If hypotension occurs as a result of overdose, the first priority should be to stabilise the cardiovascular system. To ensure normalisation of blood pressure and heart rate, the patient should be placed in a supine position. In case of severe hypotension, plasma expanders and vaso pressors should be administered. Renal function should be monitored and, if necessary, supported. As doxazosin is highly bound to plasma proteins, dialysis is not indicated as a therapeutic measure.
PHARMACOLOGICAL PROPERTIES Pharmacodynamic properties ATC code: CO2CA04 Doxazosin causes peripheral vasodilatation through a selective and competitive blockade of the postsynaptic 1 adrenoceptors. The use of doxazosin in hypertensive patients causes a fall in blood pressure due to a reduction in peripheral vascular resistance. If the medication is taken once daily, the effect can still be observed 24 hours after administration. During the onset of therapy, a gradual reduction in blood pressure occurs, and orthostatic reactions are possible. Maximum reduction in blood pressure usually occurs 2 6 hours after dosing. During therapy with doxazosin blood pressure values in hypertensive patients are similar in both supine and standing positions. No tolerance development has yet been reported in connection with the antihypertensive effect in long-term therapy with doxazosin. Occasionally, during continued use, increased plasma renin activity and tachycardia occur. Studies investigating the effect on cardiovascular morbidity and mortality are still incomplete.
Pharmacokinetic properties Doxazosin is well absorbed following oral administration. Peak plasma concentrations are reached after approximately 2 hours. Plasma elimination is biphasic, the terminal half-life is 22 hours, thereby allowing once daily dosing. Absolute bioavailability is almost 63 %. Doxazosin is 98.3 % bound to plasma proteins. Doxazosin is extensively metabolised (O-demethylation and hydroxylation) with the faeces, being the pre-dominant route of excretion, < 5 % is excreted in unchanged form in the faeces. 6hydroxy-Doxazosin is a potent and selective - blocker and in man accounts for 5 % of an oral dose. Therefore, 6hydroxy-Doxazosin contributes little to the antihypertensive activity of doxazosin. Studies in elderly patients and patients with renal insufficiency have shown no relevant pharmacokinetic differences. Only limited data are available relating to use in patients with hepatic insufficiency and to the effect of medications known to influence hepatic metabolism (e.g. cimetidine). In one clinical trial with 12 patients who had slight hepatic insufficiency, the area under the curve (AUC) was increased by 43 % and clearance after a single oral administration was reduced by 30 %. As doxazosin is almost completely metabolised in the liver, doxazosin should be used with caution in patients with impaired hepatic function (see also 4.4 Special warnings and special precautions for use).
Preclinical safety data There are no preclinical data of relevance to the prescriber other than those already mentioned in other sections of the SPC. For more information, see sections 4.3 and 4.6
PHARMACEUTICAL PARTICULARS List of excipients Lactose monohydrate, Microcrystalline Cellulose, Sodium starch Glycollate (Type A), Sodium laurylsulphate, Magnesium stearate
Incompatibilities Not applicable
PVC/ Aclar/ Aluminium blisters: 4 years
Special precautions for storage PVC/ Aclar/ Aluminium blisters: Do not store above 30C
Nature and contents of container Doxazosin Tablets 4 mg 28 tablet pack size.
Instruction for use/handling Not applicable
MARKETING AUTHORISATION HOLDER Tillomed Laboratories Ltd 3 Howard Rd Eaton Socon. St. Neots Cambs PE19 3ET, UK
MARKETING AUTHORISATION NUMBER PL 11311/0130
DATE OF FIRST AUTHORISATION / RENEWAL OF AUTHORISATION 3 August 2000
DATE OF REVISION OF THE TEXT
Source: Medicines and Healthcare Products Regulatory Agency
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