Tamsulosin

Oral
Benign prostatic hyperplasia

Pharmacogenomics:

Tamsulosin is extensively metabolised in the liver by CYP3A4 and CYP2D6 into metabolites. Genetic polymorphism of CYP2D6 gene may affect the plasma concentrations of tamsulosin. The prevalence of CYP2D6 poor metabolisers is estimated in 7% of Caucasians and 2% of African Americans. Genetic testing may be considered prior to initiation of therapy.

CYP2D6 poor metabolisers

Since CYP2D6 poor metabolisers cannot be readily identified and the potential increase in tamsulosin exposure exists only when co-administered with CYP3A4 inhibitors in CYP2D6 poor metabolisers, tamsulosin should not be used with strong CYP3A4 inhibitors (e.g. ketoconazole).

Severe: Contraindicated.

Severe: Contraindicated.

cap: Should be taken with food. Take 30 min following the same meal daily. Swallow whole, do not open/chew/crush.
prolonged release tab: May be taken with or without food. Swallow whole, do not chew/crush.
orodispersible extended-release tab: Should be taken with food. Place on the tongue & allow to dissolve. Then, swallow w/ saliva or water. 

History of orthostatic hypotension. Severe renal impairment (CrCl <10 mL/min) and hepatic impairment (Child-Pugh scores >9). Concomitant use with strong CYP3A4 inhibitors in patients who are CYP2D6 poor metabolisers.

Patient with myocardial dysfunction or angina pectoris, history of sulfonamide allergy. Cataract or glaucoma surgery patients. Not indicated for use in women.

Significant: Orthostatic hypotension, floppy iris syndrome in cataract and glaucoma surgery, hypersensitivity reactions, MI exacerbations.
Cardiac disorders: Palpitations.
Eye disorders: Blurred vision, visual impairment.
Gastrointestinal disorders: Constipation, diarrhoea, nausea, vomiting, dry mouth.
General disorders and administration site conditions: Asthenia.
Nervous system disorders: Headache, dizziness.
Reproductive system and breast disorders: Ejaculation disorders including retrograde ejaculation, ejaculation failure, priapism.
Respiratory, thoracic and mediastinal disorders: Cough, pharyngitis, sinusitis, rhinitis, epistaxis.
Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, skin desquamation, erythema multiforme, dermatitis exfoliative.
Vascular disorders: Hypotension.

PO: B

This medicine may cause drowsiness, dizziness, blurred vision or syncope, if affected, do not drive or operate machinery.

Perform prostate cancer screening prior to initiation of therapy, then as directed. Perform digital rectal examination prior to treatment, then regularly thereafter. Monitor mental alertness, blood pressure, urinalysis at baseline; signs of relief of BPH, and lower urinary tract symptoms.

Symptoms: Severe hypotensive effects, dizziness, malaise, vomiting, diarrhoea. Management: Supportive and symptomatic treatment. CV support may be given in case of acute hypotension. Lie the patient down to restore blood pressure and to normalise heart rate. For severe cases, volume expanders and vasopressors may be given. Administer activated charcoal and osmotic laxative or perform gastric lavage for ingestion of large doses.

Increased plasma concentration with moderate or strong CYP3A4 inhibitors (e.g. cimetidine, ketoconazole) and strong CYP2D6 inhibitors (e.g. paroxetine). Decreased plasma concentration with furosemide. Increased elimination rate with diclofenac and warfarin. May enhance the hypotensive effect of anaesthetic agents and other α₁-adrenoceptor blockers.

Food reduces rate and extent of absorption.

Description:
Mechanism of Action: Tamsulosin is an antagonist of α₁-adrenoceptors, which mediate smooth muscle tone in the prostate. This leads to the relaxation of smooth muscle in the bladder neck and prostate thereby improving urine flow and reducing the symptoms of benign prostatic hyperplasia (BPH).
Pharmacokinetics:
Absorption: Absorbed from the gastrointestinal tract. Bioavailability: 30% increase in fasting state. Food reduces rate and extent of absorption. Time to peak plasma concentration: 4-5 hours (fasting state); 6-7 hours (fed state).
Distribution: Volume of distribution: 16 L (immediate-release); approx 0.2 L/kg (prolonged-release). Plasma protein binding: 94-99%, mainly to α₁-acid glycoprotein.
Metabolism: Extensively and slowly metabolised in the liver by CYP3A4 and CYP2D6 to metabolites; undergoes further extensive conjugation to glucuronide or sulfate.
Excretion: Via urine (76%, <10% as unchanged drug); faeces (21%). Elimination half-life: 9-13 hours (healthy individuals); 14-15 hours (target population).

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 129211, Tamsulosin. https://pubchem.ncbi.nlm.nih.gov/compound/129211. Accessed May 30, 2023.

Store between 15-30°C.

Drugs for Bladder & Prostate Disorders

G04CA02 - tamsulosin ; Belongs to the class of alpha-adrenoreceptor antagonists. Used in the treatment of benign prostatic hypertrophy.

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