Prazosin

Registered South African indications:

• Hypertension

Contraindications

• Hypersensitivity to the active ingredient or any of its excipients
• Hypersensitivity to quinazoline

Cautions

• Pregnancy
• Breastfeeding
• Renal impairment
• Hepatic impairment
• Elderly
• Cardiac failure secondary to aortic valve stenosis, mitral valve stenosis, pulmonary embolism, recent myocardial infarction and restrictive pericardial disease
• Micturition syncope
• Cataract surgery
• May impair ability to drive and operate machinery

Forms avail. in SA and covered in this monograph: tab

Hypertension

• Oral (tab): Initial: 0.5mg, 8-12hrly; Titrate by 0.5mg at intervals of 3-7 days; Maintenance: 0.5-15mg; Max: 20mg/24hrs

When initiating, give first dosage in the evening

Cardiac failure

• Oral (tab): Initial 0.5mg, 6-12hrly; Maintenance: 4-20mg/day, in divided doses

Benign prostatic hyperplasia

• Oral (tab): Initial: 1mg, 8-12hrly; Titrate if needed; Maintenance: 2-9mg/day, in divided doses(*See additional prescribing points)

Not established for use in children below 12 years

Pregnancy

• Caution
• Prazosin hydrochloride was not teratogenic in rats and rabbits. Although no teratogenic effects were seen in animal testing, the safety of prazosin during pregnancy has not yet been established. The use of prazosin and a beta-blocker for the control of severe hypertension in 44 pregnant women revealed no drug-related foetal abnormalities or adverse effects. Therapy with prazosin was continued for as long as 14 weeks. No foetal or neonatal abnormalities have been reported with the use of prazosin hydrochloride
•  Prazosin has also been used alone or in combination with other hypotensive agents in severe hypertension of pregnancy. Prazosin should be used only when, in the opinion of the physician, potential benefit outweighs potential risk

Breastfeeding

• Caution
• Prazosin has been shown to be excreted in small amounts in human milk. Caution should be exercised when prazosin is administered to nursing mothers

Renal Impairment

• Caution; no dose adjustment recommended
  Initiate at low dosage: 0.5mg, dly; Titrate cautiously

Hepatic Impairment

• Caution; no dose adjustment recommended
  Initiate at low dosage: 0.5mg, dly; Titrate cautiously

Elderly

• Caution; no dose adjustment recommended
  Initiate at lower doses, titrate cautiously

Porphyria Information

• Not yet classified (NC)

Drugs in Sport

• Permitted - No warnings

Central Nervous System Disorders

• Depression
• Nervousness 
• Insomnia
• Hallucinations
• Dizziness
• Drowsiness 
• Headache 
• Faintness 
• Syncope
• Paraesthesia
• Worsening of pre-existing narcolepsy
• Pain
• Lack of energy

Cardiovascular Disorders

• Palpitations
• Angina pectoris 
• Tachycardia 
• Bradycardia
• Flushing
• Hypotension
• Vasculitis

Respiratory Disorders

• Dyspnoea
• Nasal congestion
• Epistaxis

Gastrointestinal Disorders

• Constipation 
• Diarrhoea 
• Dry mouth 
• Nausea and vomiting
• Abdominal discomfort
• Pancreatitis

Hepatobiliary Disorders

• Liver function abnormalities

Genitourinary Disorders

• Urinary frequency 
• Incontinence
• Impotence
• Priapism

Endocrine and Metabolic Disorders

• Oedema
• Gynaecomastia

Musculoskeletal Disorders

• Arthralgia

Skin and Subcutaneous Tissue Disorders

• Diaphoresis 
• Pruritis
• Urticaria 
• Alopecia
• Lichen planus

Immune, Blood and Lymphatic System Disorders

• Allergic reaction

Sensory Disorders

• Blurred vision 
• Eye pain 
• Reddened sclera
• Vertigo
• Tinnitus

• Beta blockers
• Calcium channel blockers
• Phosphodiesterase type-5 inhibitors

None routine

Prazosin is a selective alpha-1-adrenergic receptor antagonist whose action results in vasodilation of veins and arterioles and subsequent decrease in total peripheral resistance and blood pressure.

Tablet 1mg

• Pratsiol (Pharmacare)

Tablet 2mg

• Pratsiol (Pharmacare)