This medication can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

Tell your doctor if you regularly use other medicines that make you sleepy (such as cold or allergy medicine, narcotic pain medicine, sleeping pills, muscle relaxers, and medicine for seizures, depression, or anxiety). They can add to the side effects of clonidine and chlorthalidone.

Avoid drinking alcohol, which can increase some of the side effects of clonidine and chlorthalidone.

Avoid becoming overheated or dehydrated during exercise and in hot weather. Follow your doctor's instructions about the type and amount of liquids you should drink. In some cases, drinking too much liquid can be as unsafe as not drinking enough.

Avoid exposure to sunlight or artificial UV rays (sunlamps or tanning beds). Clonidine and chlorthalidone can make your skin more sensitive to sunlight and sunburn may result. Use a sunscreen (minimum SPF 15) and wear protective clothing if you must be out in the sun.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

• dry mouth, increased thirst, drowsiness, restless feeling, nausea, vomiting, increased urination, muscle pain or weakness, fast heart rate, feeling light-headed, fainting, or seizure (convulsions);

• easy bruising or bleeding, unusual weakness;

• red or purple spots on your skin;

• confusion, hallucinations;

• urinating more or less than usual, or not at all;

• feeling short of breath, even with mild exertion;

• swelling, rapid weight gain;

• numbness or tingly feeling; or

• nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Less serious side effects may include:

• dry mouth, loss of appetite;

• diarrhea, constipation, upset stomach;

• dizziness, drowsiness;

• headache;

• feeling restless or nervous;

• sleep problems (insomnia);

• nightmares or unusual dreams;

• breast swelling or tenderness;

• mild itching or skin rash; or

• impotence or loss of interest in sex.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all other medications you use, especially:

• other blood pressure medications;

• lithium;

• digitalis (digoxin, Lanoxin);

• insulin or diabetes medicine taken by mouth; or

• an antidepressant such as amitriptyline (Elavil, Etrafon), amoxapine (Ascendin), clomipramine (Anafranil), desipramine (Norpramin), imipramine (Janimine, Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), or trimipramine (Surmontil).

This list is not complete and there may be other drugs that can interact with clonidine and chlorthalidone. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Your pharmacist can provide more information about clonidine and chlorthalidone.