BPH and ED Pharmacology Flashcards by Zach Visinoni

What are the 3 different MOA classes used to treat BPH?

a1-adrenergic receptor antagonists

Steroid 5a-reductase inhibitors

PDE-5 inhibitors

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What are the 2 different MOA classes used to treat ED?

PDE-5 inhibitors

PGE1 agonists

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5 a1-adrenergic receptor antagonist drug names

Terazosin
Doxazosin
Tamsulosin
Silodosin
Alfuzosin

-zosin

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What is the goal of a1-adrenergic receptor antagonists?

When does relief occur?

Relax muscle tone

Rapid relief (days)

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What a1 subtypes do a1-adrenergic receptor antagonists act on?

Prostate
Detrusor m.
SC

Prostate - a1A
Detrusor m. - a1D>a1A
SC - a1D

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What happens when a1A receptors in the bladder are activated by NE?

Muscle contracts -> bladder outlet obstruction

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What happens when a1D receptors in the bladder are activated by NE?

Destrusor instability -> start and stop feeling

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What happens when a1 antagonists compete with NE? (3)

Reduce spasm
Promote muscle relaxation
Improve urine flow

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Which 2 a1-adrenergic receptor antagonist drugs have a greater specificity for a1»>a2?

Terazosin

Doxazosin

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Which 2 a1-adrenergic receptor antagonist drugs have a1A=a1D specificity?

Tamsulosin

Silodosin

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Which a1-adrenergic receptor antagonist drug is non-specific a1 selective?

Alfuzosin

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What are the adverse effects of terazosin and doxazosin?

Postural HypoTN
DIzziness
Fatigue

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What are the adverse effects of tamsulosin and silodosin?

Reduced ejaculate

IFIS

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What is an adverse effect of alfuzosin?

QT prolongation

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What drug interaction is common to all a1-adrenergic receptor antagonists?

PDE-5 inhibitors (sildenafil, vardenafil)

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Increased concentration of CYP 34A substrates is a common drug interaction with which 3 BPH meds?

Tamsulosin
Silodosin
Alfuzosin

Which a1-adrenergic receptor antagonist has an approved generic?

Tamsulosin

2 steroid 5a reductase inhibitors

Finasteride

Dutasteride

What is the overall MOA for 5a reductase inhibitors?

To decrease prostate size and inhibit enlargement

How long does it take 5a reductase inhibitos to work?

3-6 mo. It is a delayed action.

What causes the prostate to enlarge?

What is a SARs role in this?

T and DHT (DHT is 10x more potent than its T precursor).

SARs inhibit T’c conversion to DHT.

What type of SAR does a prostate that has undergone hyperplasia have?

SAR-2

2 direct effects of SAR inhibitors

2 indirect effects

Direct: T accumulation, DHT depletion

Indirect: androgen receptor is less occupied, no gene transcription occurs

Finasteride targets which SAR?

Dutasteride?

Finasteride: SAR-2

Dutasteride: SAR-1,2 (dual inhibitor, thus will lead to less serum DHT (70% reduction for Fin. and 90% reduction for Dut.))

Possible S/E for pts. on SAR inhibitors

ED Gynecomastia Dec. libido Ejaculation disturbances

SAR inhibitors do not require _______ for age or renal problems. Are there significant drug interactions? Which pts. should be cautioned to use it?

Dosage adjustments No Pts. w/ liver disease -> metabolized by CYP3A

When should combo Tx of SAR inhibitors and a1 adrenergic antagonists be used?

Severe sx of BPH Known large prostate No response to monotherapy

What drug is the lone PDE-5 inhibitor to treat BPH? Why should it be given?

Tadalafil If pt. has BPH and ED.

Risk factors for ED

Obesity Smoking Stress

What is the normal physiologic pathway to an achieve an erection? Where does PDE-5 come into play?

L-Arg (via NOS) -> NO -> cGMP -> + Ca2+ -> SM relaxes -> erection. PDE-5 turns cGMP into 5'-GMP and slows the process.

What kind of inhibition do PDE-5 inhibitors use to inhibit PDE-5?

Competitive

4 PDE-5 inhibitors to know

Sildefanil (Viagra) Vardenafil (Levitra) Tadalafil (Cialis) Avanafil (Stendra)

Which PDE-5 inhibitor has the fastest onset?

Avanafil

Which PDE-5 inhibitor has the longest duration of action?

Tadalafil

S/E of PDE-5 inhibitors

Mild. HA, dyspepsia, nasal congestion. Blurred vision (Sildenafil, vardenafil, avanafil) Back pain, myalgia (Tadalafil)

Most major contraindication to a patient taking a PDE-5 inhibitor:

Organic nitrates

How does Alprostadil treat ED?

It is PGE1 and is injected in an effect to increase cAMP levels to achieve an erection. *PGE1 agonist

Why is an erection > 4 hrs. an issue? Tx?

Blood may be clogged in penis and lead to corporal fibrosis and permanent ED (more common to Alprostadil). Phenylephrine (a sympathomimetic) and aspiration