DIBENYLINE

What it is

Dibenyline contains 10 mg phenoxybenzamine hydrochloride in capsule form. Phenoxybenzamine hydrochloride is a long acting, adrenergic α-receptor blocking agent. It increases blood flow to the skin, mucosa and abdominal viscera and lowers both supine and erect blood pressures.

Approved indications

— Hypertensive episodes associated with phaeochromocytoma. — Treatment of urinary retention due to neuropathic bladder.

Dosing overview

For phaeochromocytoma, the dosage generally required to achieve blood pressure control is 1 to 2 mg/kg body weight daily. Small initial doses (10 mg twice a day) should be slowly increased until the desired effect is obtained or adverse reactions become troublesome. The patient should be observed at each level for at least four days before instituting another increase. The dosage range is usually 20 to 60 mg daily in two doses. For urinary retention due to neurogenic bladder, 10 mg twice a day is usually sufficient. If no effect is seen in 2 to 3 weeks, alternative therapy should be used.

Key safety warnings

Case reports of carcinoma in humans after long-term treatment with phenoxybenzamine have been reported. Hence long-term use of phenoxybenzamine is not recommended. In chronic oral studies in rats, ulcerative and/or erosive gastritis of the glandular stomach occurred which was probably drug related. The clinical significance of these results is not established but they should be given due consideration in determining the benefit-risk ratio as it applies to the individual patient particularly in the younger age group. It is also recommended that treatment duration be kept as short as possible. Dibenyline-induced α-adrenergic blockade leaves β-adrenergic receptors unopposed. Compounds that stimulate both types of receptors may therefore produce an exaggerated hypotensive response and tachycardia. Dibenyline should be administered with caution in patients with marked cerebral or coronary arteriosclerosis or renal damage and in patients where tachycardia or hypotension would be undesirable. Adrenergic blocking effect may aggravate symptoms of respiratory infections.

Contraindications

Hypersensitivity to phenoxybenzamine or to any of the excipients in the formulation is a contraindication. Dibenyline is contraindicated in conditions where a fall in blood pressure is undesirable such as cerebrovascular accidents and in the recovery period following acute myocardial infarction.

PBS listing

Dibenyline 10 mg capsules are listed on the PBS as a restricted item, with an ex-manufacturer price of A$659.29.

Regulatory history

Dibenyline Capsules 10 mg were first listed on the ARTG on 14 August 1991. The sponsor date of first approval was 18 September 1990. A further ARTG registration for the blister pack formulation was listed on 29 July 2025.