Welcome to this video about diuretics.
Before we get into the details of diuretics, let's look at the basic anatomy and physiology of the kidney.
The kidney's primary function is to regulate the volume, composition, and pH of body fluids.
The normally functioning kidney retains substances needed by the body,
and eliminates those not needed by way of urine.
The nephron is the functional unit of the kidney—the kidney contains approximately 1 million nephrons.
The nephron is made up of a glomerulus and a tubule. The glomerulus being a network of capillaries,
and the tubule being a structure of epithelial cells that is divided into three main segments—
the proximal tubule, loop of Henle, and distal tubule—each differing in structure and function.
The nephron has three primary functions: glomerular filtration, tubular reabsorption, tubular secretion,
and lastly, urinary excretion.
Glomerular filtration is when arterial blood enters the glomerulus at a high pressure and the water,
electrolytes, and other solutes are pushed out of the capillaries into the Bowman's capsule and on to
the proximal tubule.
Tubular reabsorption refers to the movement of substances from the tubule to the blood in the
peritubular capillaries.
Tubular secretion indicates movement of the substances from blood in the peritubular capillaries to
glomerular filtrate flowing through the tubules.
Diuretics are drugs that increase the excretion of water, sodium, and other electrolytes through the kidneys,
thereby increasing urine formation and output.
Diuretics are given to manage edema, heart failure, and hypertension.
Diuretics act at different sites in the nephron. Their job is to decrease reabsorption of sodium and water,
and to increase urine output, therefore often referred to as a water pill.
There are three main types of diuretics:
thiazide diuretics, loop diuretics, and potassium-sparing diuretics.
There are also two types that are not used as commonly but I'll mention briefly,
carbonic anhydrase inhibitors and osmotic diuretics.
Thiazide diuretics are the most commonly used diuretic. Hydrochlorothiazide, also known as HCTZ,
is the most common thiazide drug used.
It is given for long-term management of heart failure and hypertension.
Thiazide diuretics work by decreasing the reabsorption of sodium, water, and chloride in the
distal convoluted tubule.
Thiazides are not strong diuretics because most sodium is reabsorbed before it reaches the
distal convoluted tubule and only a small amount is reabsorbed at this site.
Thiazide diuretics are well absorbed and accumulate only in the kidneys.
Diuretic effects usually begin at 2 hours and last 6 to 24 hours.
Thiazide diuretics are synthetic drugs that are chemically related to the sulfonamides, so they must be
used cautiously and patients allergic to sulfonamide drugs.
Loop diuretics are the diuretic of choice when renal function is impaired or when rapid diuretic effects
are required.
They inhibit sodium and chloride reabsorption in the ascending limb of the loop of Henle, where reabsorption
of most filtered sodium occurs.
Loop diuretics are the most effective and versatile diuretics available for clinical use.
Furosemide, or Lasix, is the most commonly used loop diuretic.
Furosemide is given for edema and hypertension.
It can be given by mouth, with dosage gradually increased to obtain the adequate diuretic
or antihypertensive response.
If it's necessary to remove the edema quickly, furosemide may be given by slow IV push.
It is also given IV for acute renal failure and hypertensive crisis.
Potassium-sparing diuretics act on the distal tubule to decrease sodium reabsorption and potassium excretion.
Potassium-sparing diuretics are weak diuretics when used alone, so are usually given in combination with a
thiazide like HCTZ that is a potassium-losing diuretic.
A major adverse effect of these drugs is hyperkalemia, or too much potassium—so patients should not be
given potassium supplements, or eat foods high in potassium, or use salt substitutes (which contain
potassium chloride rather than sodium chloride).
Potassium-sparing diuretics include spironolactone, which blocks the sodium-retaining effects of
aldosterone;
amiloride, and triamterene, which both act directly on the distal tubule to decrease the exchange of sodium
for potassium.
Now, for the two not so common diuretics I mentioned.
Carbonic anhydrase inhibitors are the weakest of the diuretics and rarely used in cardiovascular disease.
Their primary use is in the treatment of glaucoma. Drugs in this class include acetazolamide and methazolamide.
Osmotic diuretics inhibit the reabsorption of water and sodium and produce rapid diuresis.
They are given IV. A common example is mannitol, it's useful in treating oliguria or anuria and may prevent
acute renal failure during a prolonged surgery or trauma.
The major adverse effects of diuretics are fluid and electrolyte imbalances.
The most frequent problem with thiazide and loop diuretics is hypokalemia, where the potassium is
less than 3.5, sometimes requiring treatment with potassium supplements.
The potentially serious side effect of potassium-sparing diuretics is hyperkalemia, where the potassium
is greater than 5, which may lead to cardiac dysrhythmias.
Other adverse effects of potassium-losing diuretics (the thiazides and loop diuretics) include:
loss of sodium chloride, magnesium, and bicarbonate, which also occurs with diuresis,
along with changes in serum and urinary calcium levels;
dehydration; hyperglycemia; elevated serum uric acid; and ototoxicity, which is hearing impairment or loss,
tinnitus, and dizziness.
Drugs that increase the effects of diuretics are aminoglycoside antibiotics, antihypertensive drugs,
and corticosteroids.
Drugs that decrease the effects of diuretics are NSAID's, like ibuprofen and aspirin; oral contraceptives;
and vasopressors, like epinephrine and norepinephrine.
Advise your patient to tell their doctor they are taking diuretics before starting another medication.
Important things to teach your patient.
Reduce sodium intake in the diet to help diuretic drugs be more effective.
Avoid table salt and obviously salty foods as they may aggravate edema and hypertension.
When taking potassium-losing diuretics, like HCTZ, the doctor may recommend increasing intake of potassium
containing foods, like banana or orange juice, or they may prescribe a potassium supplement.
When on potassium-sparing diuretics, do not use salt substitutes as they contain potassium chloride
instead of sodium chloride.
Use protection from sunlight as diuretics cause increased sensitivity to the sun.
Do not drink alcohol or take other medications without doctor approval.
Take the diuretic early in the day, to decrease nighttime trips to the bathroom,
and take with food to decrease stomach discomfort.
I've covered a lot of information here, so feel free to go back and review,
and thank you for watching this video tutorial on diuretics.