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Renal & Urology > BPH medications - alpha-1 blockers > Flashcards

BPH medications - alpha-1 blockers Flashcards

1
Q

What is the general action of alpha-1 blockers?

A

Bind to and block the activation of adrenergic alpha-1 receptors

Causes smooth muscle relaxation

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2
Q

Name the common alpha-1 blockers used for BPH

A

Tamsulosin

Doxazosin

Terazosin

Silodosin

Alfuzosin

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3
Q

Apart from BPH, what else can alpha-1 blockers be used to treat?

A

HTN (e.g., doxazosin also used for mild to moderate HTN)

Phaeochromocytoma

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4
Q

What is the pharmacokinetic of tamsulosin?

A

Oral bioavailablity = 90%

Protein binding = 94-99% (mostly to alpha-1-acid glycoprotein)

Half-life = 14.9±3.9 hours

Metabolism = hepatic via mainly CYP3A4, 2D6

Excretion = 76% kidney via urine, 21% in faeces

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5
Q

What is the pharmacodynamic of tamsulosin?

A

Blocks alpha-1A and alpha-1D adrenoreceptors

About 70% of alpha-1 adrenoreceptors in the prostate are alpha-1A

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6
Q

What are the contraindications for alpha-1 blockers (i.e., alfuzosin, doxazosin, tamsulosin, terazosin)?

A

Severe hepatic impairment

Hx of postural hypotension

Hx of micturition syncope (i.e., fainting whilst peeing)

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7
Q

In which group of patients should you prescribe tamsulosin with caution?

A

Severe renal impairment - eGFR less than 30 mL/minute/1.73 m^2

After cataract surgery (risk of intra-operative floppy iris syndrome)

In elderly people

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8
Q

What is floppy iris syndrome?

A

Loss of muscle tone in the iris with

Symptom triad of
1. pupil constriction despite pre-operative dilatation with standard mydriatic drugs
2. fluttering and bellowing of iris stroma
3. marked tendency for the iris to prolapse towards the side port incisions

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9
Q

What are the common/very common side effects of tamsulosin?

A

dizziness

sexual dysfunction

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10
Q

What are the uncommon side effects of tamsulosin?

A

asthenia

constipation

diarrhoea

headache

nausea

palpitations

postural hypotension

rhinitis

skin reactions

vomiting

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11
Q

What are the rare/very rare side effects of tamsulosin?

A

angioedema

Stevens-Johnson syndrome

syncope

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12
Q

What are the frequency not known side effects of tamsulosin?

A

dry mouth

epistaxis

vision disorders.

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13
Q

What is the usual dose of tamsulosin modified-release preparations for BPH?

A

400 micrograms OD

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14
Q

What is the usual dose of doxazosin modified-release preparations for BPH?

A

initially 4mg OD

dose can be adjusted after 4 weeks

then increased if necessary to 8mg OD

N.B. use with caution in mild to moderate hepatic impairment, avoid in severe impairment

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15
Q

In which group of patients should you prescribe alfuzosin with caution?

A

Acute heart failure

Hx of QT-interval prolongation

Mild to moderate hepatic impairment (for immediate release preparations)

Renal impairment (for immediate release preparations)

After cataract surgery (risk of intra-operative floppy iris syndrome)

In elderly people

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16
Q

In which group of people should you not prescribe alfuzosin?

A

People with:

  • severe renal impairment (eGFR < 30mL/minute/1.73m^2)
  • hepatic impairment
17
Q

In which group of people should you not prescribe doxazosin modified release tablets?

A

People with:

  • GI obstruction
  • oesophageal obstruction or any degree of stricture
18
Q

In which group of people should you not prescribe doxazosin with caution?

A

In people with:

  • HF
  • pulmonary oedema due to aortic or mitral stenosis
  • mild to moderate hepatic impairment

After cataract surgery (due to risk of intra-operative floppy iris syndrome)

In elderly people

19
Q

In which group of people should you not prescribe terazosin with caution?

A

In people with mild to moderate hepatic impairment

After cataract surgery (due to risk of intra-operative floppy iris syndrome)

In elderly people

20
Q

What are the common/very common side effects of alfuzosin?

A

Asthenia

Diarrhoea

Dizziness

Dry mouth

Headache

Malaise

N+V

Postural hypotension

Vertigo

21
Q

What are the uncommon side effects of alfuzosin?

A

Abdominal pain

Arrhythmias

Chest pain

Drowsiness

Flushing

Oedema

Palpitations

Rhinitis

Skin reactions

Syncope

Visual impairment

22
Q

What are the rare/very rare side effects of alfuzosin?

A

Angina pectoris

Angioedema

23
Q

What are the frequency not known side effects of alfuzosin?

A

Cerebral ischaemia

Floppy iris syndrome

Hepatic disorders

Neutropenia

Priapism (long lasting painful erection - can cause permanent damage to the penis)

Thrombocytopenia

24
Q

What are the common/very common side effects of doxazosin?

A

Arrythmias

Asthenia

Chest pain

Cough

Cystitis

Dizziness

Drowsiness

Dry mouth

Dyspnoea

GI discomfort

Headache

Increased risk of infection

Influenza like illness

Muscle complaints

Nausea

Oedema

Pain

Palpitations

Skin reactions

Urinary disorders

Vertigo

25
Q

What are the uncommon side effects of doxazosin?

A

Angina pectoris

Anxiety

Abnormal appetite

Arthralgia

Constipation

Depression

Diarrhoea

GI disorders

Gout

Haemorrhage

Insomnia

MI

Abnormal sensation

Sexual dysfunction

Stroke

Syncope

Tinnitus

Tremor

Vomiting

Weight gain

26
Q

What are the rare/very rare side effects of doxazosin?

A

Alopecia

Bronchospasm

Blurred vision

Flushing

Gynaecomastia

Hepatic disorders

Leucopenia

Malaise

Muscle weakness

Thrombocytopenia

27
Q

What are the frequency not known side effects of doxazosin?

A

Floppy iris syndrome

28
Q

What are the key drug interactions of alpha-blockers?

A

alpha blockers + phosphodiesterase-5 inhibitors (PDE5 inhibitor) e.g., sildenafil, tadalafil, or vardenafil = symptomatic hypotension
- to minimise the risk of postural hypotension, the person should be stable on the alpah-blocker before starting a PDE5 inhibitor

alpha-blockers + ACEi/CCB/Beta-blockers/nitrates/diuretics/moxisylyte = additive hypotensive effect

alpha-blockers + CYP3A4 inhibitors (e.g., clarithromycin, itraconazole and ritonavir) = increased exposure to tamsulosin, alfuzosin, doxazosin

29
Q

Sources

A

https://cks.nice.org.uk/topics/luts-in-men/prescribing-information/alpha-blockers/

https://go.drugbank.com/categories/DBCAT000696

Renal & Urology (7 decks)

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