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Showing posts with label Genitourinary drugs. Show all posts
Showing posts with label Genitourinary drugs. Show all posts
Hormonal contraceptives
By Piscean | Monday, April 25, 2011 | Posted in , , | With 0 comments

Hormonal contraceptives
Hormonal contraceptives inhibit ovulation. Contraceptives typically contain a combination of hormones. For example, ethinyl estradiol may be combined with desogestrel, drospirenone, levonorgestrel, norethindrone, norgestimate, or norgestrel. Also, mestranol may be combined with norethindrone. Ethinyl estradiol or ethynodiol diacetate may also be used alone as a contraceptive.
Pharmacokinetics
Hormonal contraceptives are absorbed from the GI tract and are widely distributed. They’re metabolized in the kidneys and excreted in urine and feces.
Patch power
Some forms of hormonal contraceptives are available in a transdermal patch form. These contraceptives are absorbed through the skin but have the same distribution, metabolism, and excretion as orally administered contraceptives.
Pharmacodynamics
The primary mechanism of action of combination hormonal contraceptives (estrogen and progestin) is the suppression of gonadotropins, which inhibits ovulation. Estrogen suppresses secretion of follicle-stimulating hormone, which blocks follicular development and ovulation. Progestin suppresses the secretion of luteinizing hormone, which prevents ovulation, even if the follicle develops. Progestin also thickens the cervical mucus; this interferes with sperm migration and causes endometrial changes that prevent implantation of a fertilized ovum.
Pharmacotherapeutics
The primary purpose for taking hormonal contraceptives is the prevention of pregnancy in women. The combination of ethinyl estradiol and norgestimate is also used to treat moderate acne in females younger than age 15.

Drug interactions
Hormonal contraceptives can interact with other medications in various ways:
  • Antibiotics, oxcarbazepine, phenobarbital, phenytoin, topiramate, and modafinil may decrease the effectiveness of oral contraceptives. A patient taking these drugs with a hormonal contraceptive needs to use a barrier contraceptive.
  • Atorvastatin may increase serum estrogen levels.
  • Cyclosporin and theophylline have an increased risk of toxicity when taken with hormonal contraceptives.
  • Prednisone increases the therapeutic and possibly toxic effects of hormonal contraceptives. 
  • Several herbal medications can affect serum levels of hormonal contraceptives.
Warning!
Adverse reactions to hormonal contraceptives
Potentially serious adverse reactions to hormonal contraceptives include arterial thrombosis, thrombophlebitis, pulmonary embolism, myocardial infarction, cerebral hemorrhage or thrombosis, hypertension, gallbladder disease, and hepatic adenomas.
Other adverse reactions include:
  • acne
  • bleeding or spotting between menstrual periods
  • bloating
  • breast tenderness or enlargement
  • changes in libido
  • diarrhea
  • difficulty wearing contact lenses
  • unusual hair growth
  • weight fluctuations
  • upset stomach
  • vomiting.


Erectile dysfunction therapy drugs
By Piscean | | Posted in , | With 1 comments

Erectile dysfunction therapy drugs
Erectile dysfunction therapy drugs treat penile erectile dysfunction that results from a lack of blood flowing through the corpus cavernosum. This type of erectile dysfunction usually stems from vascular and neurologic conditions. Drugs used for erectile dysfunction include alprostadil, sildenafil, tadalafil, and vardenafil.
Warning!
Adverse reactions to urinary tract antispasmodics
Possible adverse reactions to urinary tract antispasmodics include:
  • blurred vision
  • headache
  • somnolence
  • urinary retention
  • dry mouth
  • dyspepsia
  • constipation
  • nausea
  • vomiting
  • weight gain
  • pain
  • acute and secondary angle-closure glaucoma.
Pharmacokinetics
Erectile dysfunction drugs are well absorbed in the GI tract. Distribution of these drugs isn’t known. The majority of these drugs’including sildenafil, tadalafil, and vardenafil’are given orally, metabolized in the liver, and excreted in feces.
An exceptional drug
Alprostadil is the exception: it’s administered directly into the corpus cavernosum, metabolized in the lungs, and excreted in urine.
Pharmacodynamics
Sildenafil, tadalafil, and vardenafil selectively inhibit the phosphodiesterase type 5 receptors, which causes an increase in blood levels of nitric oxide. This increase in nitric oxide levels activates the cGMP enzyme, which relaxes smooth muscles and allows blood to flow into the corpus cavernosum, causing an erection.
Alprostadil acts locally, promoting smooth muscle relaxation, which causes an increase in blood flow to the corpus cavernosum and produces an erection.



Warning!
Adverse reactions to erectile dysfunction drugs
Adverse reactions to erectile dysfunction drugs include:
  • decreased supine blood pressure and cardiac output
  • increased risk of cardiovascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmias, cerebrovascular hemorrhage, transient ischemic attack, and hypertension
  • headache
  • dizziness
  • flushing
  • dyspepsia
  • vision changes
  • prolonged erections (more than 4 hours), which can result in irreversible damage to erectile tissue
  • penile pain (with alprostadil).
Pharmacotherapeutics
Alprostadil, sildenafil, tadalafil, and vardenafil are all used in the treatment of erectile dysfunction. Sildenafil is also indicated for the treatment of pulmonary arterial hypertension.
Drug interactions
Erectile dysfunction drugs may interact with other drugs in the following ways:
  • Nitrates and alpha-adrenergic blockers used in combination with erectile dysfunction drugs may cause severe hypotension and potentially serious cardiac events.
  • Ketoconazole, itraconazole, and erythromycin may result in increased levels of vardenafil or tadalafil.
  • Protease inhibitors, such as indinavir or ritonavir, may cause increased tadalafil or vardenafil levels


Urinary tract antispasmodics
By Piscean | | Posted in , | With 2 comments

Urinary tract antispasmodics
Urinary tract antispasmodics help decrease urinary tract muscle spasms. They include darifenacin, flavoxate, oxybutynin, solifenacin, tolterodine, and trospium.
Pharmacokinetics
Flavoxate, oxybutynin, tolterodine, darifenacin, and solifenacin are most often administered orally and are rapidly absorbed. Trospium is administered orally but is poorly absorbed. Oxybutynin is also available as a dermal patch. These drugs are all widely distributed, metabolized in the liver, and excreted in urine. Urinary tract antispasmodics also cross the placenta and are excreted in breast milk.
Pharmacodynamics
Urinary tract antispasmodics relieve smooth muscle spasms by inhibiting parasympathetic activity, which causes the detrusor and urinary muscles to relax. Flavoxate and oxybutynin also exhibit many anticholinergic effects.
Pharmacotherapeutics
Urinary tract antispasmodics are used for patients with overactive bladders who have symptoms of urinary frequency, urgency, or incontinence.
Now I get it!
How oxybutynin works
When acetylcholine is released within the bladder, it attaches to receptors on the surface of smooth muscle in the bladder, stimulating bladder contractions. Oxybutynin suppresses these involuntary contractions by blocking the release of acetylcholine. This anticholinergic effect is what makes oxybutynin useful in the treatment of overactive bladder.
Urgent symptoms
Trospium is also indicated for patients with overactive bladders who have symptoms of urge urinary incontinence, and oxybutynin acts as an antispasmodic for uninhibited or reflex neurogenic bladder. 
Drug interactions
Urinary tract antispasmodics have few drug interactions:
  • Use with anticholinergic agents may increase dry mouth, constipation, and other anticholinergic effects. 
  • Urinary tract antispasmodics may decrease the effectiveness of phenothiazines and haloperidol.
  • Trospium may interfere with the elimination of certain drugs excreted through the kidneys (such as digoxin, metformin, and vancomycin), resulting in increased blood levels of these drugs


Carbonic anhydrase inhibitors
By Piscean | | Posted in , | With 0 comments

Carbonic anhydrase inhibitors
Carbonic anhydrase inhibitors are diuretics that block the action of carbonic anhydrase. They include acetazolamide and methazolamide.
Pharmacokinetics
Carbonic anhydrase inhibitors are absorbed through the GI tract. Some systemic absorption also occurs after ophthalmic administration. They’re distributed in tissues with high carbonic anhydrase content, such as erythrocytes, plasma, kidneys, eyes, liver, and muscle. Carbonic anhydrase inhibitors are excreted by the kidneys in urine.
Pharmacodynamics
In the kidneys, carbonic anhydrase inhibitors decrease the availability of hydrogen ions, which blocks the sodium-hydrogen exchange mechanisms. As a result, urinary excretion of sodium, potassium, bicarbonate, and water increases.

Don’t lose your sense of humor
In the eyes, carbonic anhydrase inhibition reduces aqueous humor production, which reduces intraocular pressure.
Pharmacotherapeutics
Carbonic anhydrase inhibitors are used for diuresis and to treat glaucoma. Acetazolamide may also be used to treat epilepsy and acute mountain sickness.
Drug interactions
Carbonic anhydrase inhibitors produce a variety of drug interactions:
  • Salicylates may cause carbonic anhydrase inhibitor toxicity, including central nervous system depression and metabolic acidosis.
  • Diflunisal may increase intraocular pressure when given with a carbonic anhydrase inhibitor.
  • Acetazolamide used concurrently with cyclosporine may increase cyclosporine levels and the risk of neurotoxicity.
  • Acetazolamide used concurrently with primidone may decrease serum and urine levels of primidone. 
Warning!
Adverse reactions to carbonic anhydrase inhibitors
Adverse reactions to carbonic anhydrase inhibitors include:
  • hypokalemia
  • metabolic acidosis
  • electrolyte imbalances.


Osmotic diuretics
By Piscean | | Posted in , , | With 0 comments

Osmotic diuretics
Osmotic diuretics cause diuresis through osmosis, moving fluid into the extracellular spaces. They include mannitol and urea.
Pharmacokinetics
Administered I.V. for rapid distribution, osmotic diuretics are freely filtered by the glomeruli of the kidney’except for mannitol, which is only slightly metabolized. Osmotic diuretics are excreted primarily in urine.
Pharmacodynamics
Osmotic diuretics receive their name because they increase the osmotic pressure of the glomerular filtrate, which inhibits the reabsorption of sodium and water. They create an osmotic gradient in the glomerular filtrate and the blood. In the glomerular filtrate, the gradient prevents sodium and water reabsorption. In the blood, the gradient allows fluid to be drawn from the intracellular into the intravascular spaces.
Pharmacotherapeutics
Osmotic diuretics are used to treat acute renal failure and cerebral edema and to reduce intracranial and intraocular pressure. Mannitol is used to promote diuresis in acute renal failure and to promote urinary excretion of toxic substances.
Drug interactions
Taking osmotic diuretics with lithium may increase renal excretion of lithium, which in turn decreases the effectiveness of lithium. Patients taking both drugs require lithium level monitoring.
Warning!
Adverse reactions to osmotic diuretics
Adverse reactions to osmotic diuretics include:
  • hyponatremia
  • dehydration
  • circulatory overload (from osmotic effects)
  • thrombophlebitis or local irritation at the infusion site


Potassium-sparing diuretics
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Potassium-sparing diuretics
Potassium-sparing diuretics have weaker diuretic and antihypertensive effects than other diuretics but provide the advantage of conserving potassium. These drugs include amiloride, spironolactone, and triamterene.
Pharmacokinetics
Potassium-sparing diuretics are only available orally and are absorbed in the GI tract. They’re metabolized by the liver (except for amiloride, which isn’t metabolized) and excreted primarily in urine.
Pharmacodynamics
The direct action of potassium-sparing diuretics on the distal tubule of the kidneys results in urinary excretion of sodium, water, bicarbonate, and calcium. The drug also decreases the excretion of potassium and hydrogen ions. These effects lead to reduced blood pressure and increased serum potassium levels.
Compare and contrast
Structurally similar to aldosterone, spironolactone acts as an aldosterone antagonist. Aldosterone promotes the retention of sodium and water and the loss of potassium, whereas spironolactone counteracts these effects by competing with aldosterone for receptor sites. As a result, sodium, chloride, and water are excreted and potassium is retained.
Pharmacotherapeutics
Potassium-sparing diuretics are used to treat:
  • edema
  • diuretic-induced hypokalemia in patients with heart failure
  • cirrhosis
  • nephrotic syndrome (abnormal condition of the kidneys)
  • heart failure
  • hypertension.
A hairy situation
Spironolactone also is used to treat hyperaldosteronism (excessive secretion of aldosterone) and hirsutism (excessive hair growth), including hirsutism associated with Stein-Leventhal

(polycystic ovary) syndrome. Potassium-sparing diuretics are commonly used with other diuretics to potentiate their action or counteract their potassium-wasting effects.
Drug interactions
Giving potassium-sparing diuretics with potassium supplements or angiotensin-converting enzyme inhibitors increases the risk of hyperkalemia. Concurrent use of spironolactone and digoxin increases the risk of digoxin toxicity.
Warning!
Adverse reactions to potassium-sparing diuretics
Few adverse drug reactions occur with potassium-sparing diuretics. However, their potassium-sparing effects can lead to hyperkalemia, especially if given with a potassium supplement or high-potassium diet.


Loop diuretics
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Loop diuretics
Loop (high ceiling) diuretics are highly potent drugs. They include bumetanide, ethacrynic acid, and furosemide.

Pharmacokinetics
Loop diuretics are absorbed well in the GI tract and are rapidly distributed. These diuretics are highly protein bound. They undergo partial or complete metabolism in the liver, except for furosemide, which is excreted primarily unchanged. Loop diuretics are excreted primarily by the kidneys.
Pharmacodynamics
Loop diuretics are the most potent diuretics available, producing the greatest volume of diuresis (urine production). Bumetanide’which is 40 times more potent than furosemide’is the shortest-acting diuretic. Loop diuretics also have a high potential for causing severe adverse reactions.
 
Warning!
Loop diuretics warning
Loop diuretics, with the exception of ethacrynic acid, contain sulfa. A patient who has an allergy to sulfa may experience an allergic reaction to loop diuretics. Use with caution, and alert the patient to this possibility.
The scoop on the loop
Loop diuretics received their name because they act primarily on the thick, ascending loop of Henle (the part of the nephron responsible for concentrating urine) to increase the secretion of sodium, chloride, and water. These drugs also inhibit sodium, chloride, and water reabsorption in the proximal tubule.
Pharmacotherapeutics
Loop diuretics are used to treat edema associated with renal disease, hepatic cirrhosis, and heart failure, as well as to treat hypertension (usually with a potassium-sparing diuretic or potassium supplement to prevent hypokalemia).
Ethacrynic acid may also be used for the short-term management of ascites due to malignancy, idiopathic edema, or lymphedema. Furosemide may be used with mannitol to treat cerebral edema.
Drug interactions
Loop diuretics produce a variety of drug interactions:
  • The risk of ototoxicity (damage to the organs of hearing) increases when aminoglycosides and cisplatin are taken with loop diuretics (especially with high doses of furosemide). 
  • Loop diuretics reduce the hypoglycemic effects of oral antidiabetic drugs, possibly resulting in hyperglycemia.
  • These drugs may increase the risk of lithium toxicity.
  • The risk of electrolyte imbalances that can trigger arrhythmias increases when cardiac glycosides and loop diuretics are taken together.

  • Use with digoxin may cause additive toxicity, increasing the risk of digoxin toxicity and arrhythmias.
Warning!
Adverse reactions to loop diuretics
The most common adverse reactions to loop diuretics include:
  • fluid and electrolyte imbalances (including metabolic alkalosis, hypovolemia, hypochloremia, hypochloremic alkalosis, hyperglycemia, hyperuricemia, dehydration, hyponatremia, hypokalemia, and hypomagnesemia)
  • transient deafness
  • tinnitus
  • diarrhea
  • nausea
  • vomiting
  • abdominal pain
  • impaired glucose tolerance
  • dermatitis
  • paresthesia
  • hepatic dysfunction
  • photosensitivity
  • orthostatic hypotension


Diuretics
By Piscean | | Posted in , , | With 0 comments
Diuretics
Diuretics trigger the excretion of water and electrolytes from the kidneys, making these drugs a primary choice in the treatment of renal disease, edema, hypertension, and heart failure.
Thiazide and thiazide-like diuretics
Derived from sulfonamides, thiazide and thiazide-like diuretics are used to treat edema and to prevent the development and recurrence of renal calculi. They’re also used for such cardiovascular diseases as hypertension and heart failure.
Thiazide diuretics include:
  • bendroflumethiazide
  • chlorothiazide
  • hydrochlorothiazide
  • hydroflumethiazide
  • methyclothiazide
  • polythiazide.
Thiazide-like diuretics include:
  • chlorthalidone
  • indapamide
  • metolazone.
Pharmacokinetics (how drugs circulate)
Thiazide diuretics are absorbed rapidly but incompletely from the GI tract after oral administration. They cross the placenta and are secreted in breast milk. These drugs differ in how well they’re metabolized, but all are excreted primarily in urine.
Thiazide-like diuretics are absorbed from the GI tract. Chlorthalidone is 90% bound to erythrocytes; little is known about its metabolism. Indapamide is distributed widely into body tissues and metabolized in the liver. Little is also known about the metabolism of metolazone. All of these drugs are primarily excreted in urine.
Pharmacodynamics (how drugs act)
Thiazide and thiazide-like diuretics promote the excretion of water by preventing the reabsorption of sodium in the kidneys. As the kidneys excrete the excess sodium, they excrete water along with it. These drugs also increase the excretion of chloride, potassium, and bicarbonate, which can result in electrolyte imbalances. With long-term use, thiazide diuretics also lower blood pressure by causing arteriolar vasodilation.
Turning down the volume
Initially, diuretic drugs decrease circulating blood volume, leading to reduced cardiac output. However, if therapy is maintained, cardiac output stabilizes but plasma fluid volume decreases.
Pharmacotherapeutics (how drugs are used)
Thiazides are used for the long-term treatment of hypertension; they’re also used to treat edema caused by kidney or liver disease, mild or moderate heart failure, and corticosteroid and estrogen therapy. Because these drugs decrease the level of calcium in urine, they may be used alone or with other drugs to prevent the development and recurrence of renal calculi.
Pointing out a paradox
 
In patients with diabetes insipidus (a disorder characterized by excessive urine production and excessive thirst resulting from reduced secretion of antidiuretic hormone), thiazides paradoxically decrease urine volume, possibly through sodium depletion and plasma volume reduction.
Warning!
Adverse reactions to thiazide and thiazide-like diuretics
The most common adverse reactions to thiazide and thiazide-like diuretics include:
  • reduced blood volume
  • orthostatic hypotension
  • hypokalemia
  • hyperglycemia
  • hyponatremia.
Drug interactions
Drug interactions related to thiazide and thiazide-like diuretics result in altered fluid volume, blood pressure, and serum electrolyte levels:
  • These drugs may decrease excretion of lithium, causing lithium toxicity.
  • Nonsteroidal anti-inflammatory drugs, including cyclooxygenase-2 (COX-2) inhibitors, may reduce the antihypertensive effect of these diuretics.
  • Use of these drugs with other potassium-depleting drugs and digoxin may cause an additive effect, increasing the risk of digoxin toxicity.
  • These diuretics may increase the response to skeletal muscle relaxants.
  • Use of these drugs may increase blood glucose levels, requiring higher doses of insulin or oral antidiabetic drugs.
  • These drugs may produce additive hypotension when used with antihypertensives


Genitourinary drugs
By Piscean | | Posted in , | With 0 comments

Genitourinary drugs
Just the facts
In this chapter, you’ll learn:
  • classes of drugs used to treat genitourinary (GU) disorders
  • uses and varying actions of these drugs
  • absorption, distribution, metabolization, and excretion of these drugs
  • drug interactions and adverse reactions to these drugs.
Drugs and the genitourinary system
The GU system consists of the reproductive system (the sex organs) and the urinary system, which includes the kidneys, ureters, bladder, and urethra. The kidneys perform most of the work of the urinary system.
Multitalented
The kidneys perform several vital tasks, including:
  • disposing of wastes and excess ions in the form of urine
  • filtering blood, which regulates its volume and chemical makeup
  • helping to maintain fluid, electrolyte, and acid-base balances
  • producing several hormones and enzymes
  • converting vitamin D to a more active form
  • helping to regulate blood pressure and volume by secreting renin.

Helping hands
Types of drugs used to treat GU disorders include:
  • diuretics
  • urinary tract antispasmodics
  • erectile dysfunction therapy drugs
  • hormonal contraceptives.