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Clorpres Side Effects

Generic name: chlorthalidone / clonidine

Medically reviewed by Last updated on Jun 24, 2022.

Note: This document contains side effect information about chlorthalidone / clonidine. Some dosage forms listed on this page may not apply to the brand name Clorpres.

Applies to chlorthalidone/clonidine: oral tablet.

Serious side effects of Clorpres

Along with its needed effects, chlorthalidone / clonidine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking chlorthalidone / clonidine:

Signs and symptoms of overdose

  • Difficulty in breathing
  • dizziness (extreme) or faintness
  • feeling cold
  • pinpoint pupils of eyes
  • slow heartbeat
  • unusual tiredness or weakness (extreme)

Check with your doctor as soon as possible if any of the following side effects occur while taking chlorthalidone / clonidine:

Signs and symptoms of too much potassium loss

Signs and symptoms of too much sodium loss

  • Confusion
  • convulsions (seizures)
  • decreased mental activity
  • irritability
  • muscle cramps
  • unusual tiredness or weakness

Less common

  • Mental depression
  • swelling of feet and lower legs


  • Black, tarry stools
  • blood in urine or stools
  • cough or hoarseness
  • fever or chills
  • joint pain
  • lower back or side pain
  • paleness or cold feeling in fingertips and toes
  • pinpoint red spots on skin
  • skin rash or hives
  • stomach pain (severe) with nausea and vomiting
  • unusual bleeding or bruising
  • vivid dreams or nightmares
  • yellow eyes or skin

Other side effects of Clorpres

Some side effects of chlorthalidone / clonidine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Constipation
  • dizziness
  • drowsiness
  • dryness of mouth
  • unusual tiredness or weakness

Less common

  • Decreased sexual ability
  • diarrhea
  • dizziness or lightheadedness when getting up from a lying or sitting position
  • dry, itching, or burning eyes
  • increased sensitivity of skin to sunlight
  • loss of appetite
  • nausea or vomiting
  • nervousness
  • upset stomach

After you stop using this medicine, it may still produce some side effects that need attention. During this period of time, Check with your doctor immediately if you notice the following side effects:

  • Anxiety or tenseness
  • chest pain
  • fast or pounding heartbeat
  • headache
  • increased salivation
  • nausea
  • nervousness
  • restlessness
  • shaking or trembling of hands and fingers
  • stomach cramps
  • sweating
  • trouble in sleeping
  • vomiting

For Healthcare Professionals

Applies to chlorthalidone / clonidine: oral tablet.


The most frequent adverse reactions were dry mouth, drowsiness, dizziness, constipation, and sedation.[Ref]


Very common (10% or more): Dry mouth (up to 40%), constipation (up to 10%)


Frequency not reported: Gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, pancreatitis


Common (1% to 10%): Nausea, vomiting

Frequency not reported: Parotitis[Ref]

Nervous system

Very common (10% or more): Drowsiness (up to 33%), dizziness (up to 16%), sedation (up to 10%)


Frequency not reported: Dizziness, vertigo, paresthesias, headache


Common (1% to 10%): Headache[Ref]



Frequency not reported: Weakness


Very common (10% or more): Weakness (up to 10%)

Common (1% to 10%): Malaise, fatigue, discontinuation syndrome

Uncommon (0.1% to 1%): Gynecomastia

Frequency not reported: Dryness, increased sensitivity to alcohol, fever[Ref]



Frequency not reported: Necrotizing angiitis, orthostatic hypotension


Common (1% to 10%): Orthostatic symptoms

Uncommon (0.1% to 1%): Palpitations, tachycardia, bradycardia

Frequency not reported: Raynaud's phenomenon, congestive heart failure, ECG abnormalities, sinus bradycardia, atrioventricular block, pallor[Ref]



Frequency not reported: Purpura, photosensitivity, rash, urticaria, Lyell's syndrome


Common (1% to 10%): Rash

Uncommon (0.1% to 1%): Pruritus, hives, angioneurotic edema, urticaria, alopecia[Ref]



Frequency not reported: Glycosuria, impotence


Common (1% to 10%): Sexual activity decreased, impotence, nocturia

Uncommon (0.1% to 1%): Difficulty in micturition, urinary retention[Ref]



Frequency not reported: Leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia


Frequency not reported: Weakly positive Coombs' test[Ref]



Frequency not reported: Intrahepatic cholestatic jaundice


Common (1% to 10%): Mild transient abnormalities in liver function tests

Frequency not reported: Hepatitis[Ref]



Frequency not reported: Anorexia, hyperglycemia, hyperuricemia


Common (1% to 10%): Anorexia, weight gain

Frequency not reported: Transient elevation of blood glucose[Ref]



Frequency not reported: Muscle spasm


Uncommon (0.1% to 1%): Muscle or joint pain, cramps of the lower limbs

Frequency not reported: Transient elevation of serum creatine phosphokinase[Ref]



Frequency not reported: Xanthopsia


Frequency not reported: Burning of the eyes, blurred vision[Ref]



Frequency not reported: Restlessness


Common (1% to 10%): Nervousness, agitation, mental depression, loss of libido

Uncommon (0.1% to 1%): Insomnia

Frequency not reported: Vivid dreams, nightmares, behavioral changes, restlessness, anxiety, visual and auditory hallucinations, delirium[Ref]



Frequency not reported: Dryness of the nasal mucosa[Ref]


1. "Product Information. Combipres (chlorthalidone-clonidine)." Apothecon Inc (2022):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.