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Hydrochlorothiazide: Dr. Peter Rice


If you ever find yourself as a pharmacy technician or pharmacy student, you’ll be fixated on memorizing the top drugs. When you get to hydrochlorothiazide, two things happen.  First, the name is so long that almost no one says the full name. It’s abbreviated to HCTZ.  Second, there are two brand names to memorize – Hydrodiuril and Esidrix – except that they are no longer sold in the US.

Hydorochlorothiazide is one of the most popular drugs in the US.  Discovered by Ciba Pharmaceutical Company chemist George deStevens  in the 1955, it is one of the most widely used medications for blood pressure.  Hydrochlorothiazide was originally marketed under the brand names Hydrodiuril™ and Esidrix™,  It is currently available only as a generic medicine, alone and in combination with approximately 28 other drugs.

Hydrochlorothiazide is the prototype for a class of drugs called thiazide diuretics.  

The thiazides act in the kidney. The basic unit of activity in the kidney is the nephron; the nephron filters blood plasma to start the process of making urine which is then changes by absorption and secretion of various ions (mainly sodium and potassium) and water as the filtrate moves toward the bladder. Water usually follows ions that move out of the filtrate, and thiazide diuretics inhibit the absorption of sodium from the distal convoluted tubule, the later portion of the nephron.  Sodium chloride remains in filtrate and helps carry water out of the body in the urine. HCTZ acts from the inside of the nephron, called the lumen, so some kidney function is required to get HCTZ to its site of action.



Hydrochlorothiazide, HCTZ, is a first-line drug for hypertension.

It causes the body to excrete more sodium and chloride in the urine, and to lose excess water. About 70% of patients taking Hydrochlorothiazide for hypertension will find it to be an effective drug.

While its main therapeutic use is for hypertension, HCTZ is often used for fluid retention and edema. HCTZ is absorbed orally and has its onset of diuresis within two hours; its diuretic effects last 4 to 6 hours.  HCTZ and other diuretics should typically be taken in the morning, and with a full glass of water to help them work. Patients taking their diuretic drugs at bedtime frequently report “insomnia”; they have trouble getting to sleep or sleep poorly because they have to use bathroom frequently.

Like all drugs, Hydrochlorothiazide is associated with side effects, some of which can be minimized. Through its action on the kidneys, HCTZ can result in the unintentional loss of certain ions and can contribute to low potassium and low sodium. HCTZ can increase LDL cholesterol and impair blood glucose control, so it can worsen control of diabetes. HCTZ also appears to decrease release of insulin and utilization of insulin by tissues, but hypokalemia may contribute to these effects.

Pharmacists and prescribers often recommend that patients taking diuretics like HCTZ eat foods that contain potassium –bananas are a good source for potassium.

You should avoid HCTZ if you are allergic to it. Chemically, Hydrochlorothiazide contains a sulfonamide group, so if you are allergic to sulfa antibiotics you might be allergic to Hydrochlorothiazide as well.  HCTZ can also worsen gout and should be avoided in patients with gout.

Hydrochlorothiazide is one of many drugs that can produce photosensitivity- making it easier to sunburn- or skin rash. Patients should discontinue the drug immediately if there is a skin complication or concern and check with their pharmacist or prescriber before continuing.

With its high rate of effectiveness for hypertension, low incidence of serious adverse effects and low cost, it’s no wonder that hydrochlorothiazide remains so popular. BUT, it’s not the only choice for hypertension and sometimes other medicines should be considered for hypertension in the presence of other disease states, like diabetes.

Your pharmacist can help you understand your medicines and how they fit into the comprehensive management of your health. Stop by your community pharmacy and ask about any concerns you have about your medicines. Pharmacists are there to help you take care of yourself.


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Dr. Peter J. Rice

Dr. Peter J. Rice is a professor of Pharmacology emeritus at the East Tennessee State University Quillen College of Medicine and Professor of Clinical Pharmacy at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences. He received his BS in pharmacy from Northeastern University, PhD in pharmacology from the Ohio State University and PharmD from the University of Kentucky. He is a Board Certified Pharmacotherapy Specialist and practices in the ambulatory care and community pharmacy settings. Professor Rice is the author of Understanding Drug Action: An introduction to pharmacology (APhA, 2014) and is a fellow of the American Pharmacists Association.




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