Drugs List

Therapeutic Indications

Uses

Hypertension - due to phaeochromocytoma

Contraindications

Neonates
Cerebrovascular accident
Galactosaemia
Porphyria
Within 1 month of a myocardial infarction

Precautions and Warnings

Children 1 month to 18 years
Elderly
Breastfeeding
Cerebrovascular disorder
Congestive cardiac failure
Glucose-galactose malabsorption syndrome
Ischaemic heart disease
Lactose intolerance
Pregnancy
Renal impairment
Severe cardiac disorder

Advise patient dizziness may affect ability to drive or operate machinery
Contains lactose
Staff & patient: Risk of contact sensitisation,avoid contamination of hands
Advise patient that postural hypotension may occur
Potentially mutagenic and carcinogenic

Phenoxybenzamine has been shown to be carcinogenic and mutagenic in animal and bacterial models and so should only be used after very careful consideration of the risks in patients in which alternative treatment is inappropriate.

Pregnancy and Lactation

Pregnancy

Use phenoxybenzamine with caution during pregnancy.
The manufacturer states that there is little evidence for the safety of phenoxybenzamine use during pregnancy and thus should not be used unless considered essential.
Schaefer (2015) suggests that phenoxybenzamine can be used during pregnancy. If phenoxybenzamine is used during the first trimester, a follow-up sonography should be offered to verify normal development of the foetus.
Maternal alpha-blockade may reduce or eliminate the adverse effect of hypertension on placental perfusion and subsequently reduce the risk of poor foetal health. No adverse effects have been reported in the limited data available (Briggs, 2015).
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Use phenoxybenzamine with caution during breastfeeding.
Schaefer (2015) suggests that phenoxybenzamine should not be used during breastfeeding. If the mother is taking phenoxybenzamine, the infant should not be weaned but a change is therapy is recommended.
The molecular weight of the drug (about 340) is low enough such that excretion of the drug into breast milk should be expected. Potential adverse effects on the infant are unknown (Briggs, 2015).
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Side Effects

Contact sensitisation
Dizziness
Failure of ejaculation
Gastro-intestinal symptoms
Lassitude
Miosis
Nasal congestion
Postural hypotension
Tachycardia

Presentation

Oral formulations containing phenoxybenzamine hydrochloride

Drugs List

Therapeutic Indications

Uses

Hypertension - due to phaeochromocytoma

Dosage

Adults

Elderly

Children

Contraindications

Neonates
Cerebrovascular accident
Galactosaemia
Porphyria
Within 1 month of a myocardial infarction

Precautions and Warnings

Children 1 month to 18 years
Elderly
Breastfeeding
Cerebrovascular disorder
Congestive cardiac failure
Glucose-galactose malabsorption syndrome
Ischaemic heart disease
Lactose intolerance
Pregnancy
Renal impairment
Severe cardiac disorder

Advise patient dizziness may affect ability to drive or operate machinery
Contains lactose
Staff & patient: Risk of contact sensitisation,avoid contamination of hands
Advise patient that postural hypotension may occur
Potentially mutagenic and carcinogenic

Phenoxybenzamine has been shown to be carcinogenic and mutagenic in animal and bacterial models and so should only be used after very careful consideration of the risks in patients in which alternative treatment is inappropriate.

Pregnancy and Lactation

Pregnancy

Use phenoxybenzamine with caution during pregnancy.
The manufacturer states that there is little evidence for the safety of phenoxybenzamine use during pregnancy and thus should not be used unless considered essential.
Schaefer (2015) suggests that phenoxybenzamine can be used during pregnancy. If phenoxybenzamine is used during the first trimester, a follow-up sonography should be offered to verify normal development of the foetus.
Maternal alpha-blockade may reduce or eliminate the adverse effect of hypertension on placental perfusion and subsequently reduce the risk of poor foetal health. No adverse effects have been reported in the limited data available (Briggs, 2015).
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Use phenoxybenzamine with caution during breastfeeding.
Schaefer (2015) suggests that phenoxybenzamine should not be used during breastfeeding. If the mother is taking phenoxybenzamine, the infant should not be weaned but a change is therapy is recommended.
The molecular weight of the drug (about 340) is low enough such that excretion of the drug into breast milk should be expected. Potential adverse effects on the infant are unknown (Briggs, 2015).
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Side Effects

Contact sensitisation
Dizziness
Failure of ejaculation
Gastro-intestinal symptoms
Lassitude
Miosis
Nasal congestion
Postural hypotension
Tachycardia

Overdosage

It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

The following number will direct the caller to the relevant local centre (0844) 892 0111

Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Further Information

Last Full Review Date: January 2017

Reference Sources

Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

Summary of Product Characteristics: Phenoxybenzamine 10mg Capsules. Concordia International. Revised November 2015.

NICE Evidence Services Available at: www.nice.org.uk Last accessed: 13 September 2017