Meds and you

27 September 2013

Atenolol and chlorthalidone

The combination of atenolol and chlorthalidone is a combination of beta-receptor blocker and a diuretic.


The combination of atenolol and chlorthalidone is the active ingredient of Adco-Loten tablets (Nappi code: 791172-007), Sandoz Co-Tenidone tablets (Nappi code: 789607-018, 034 & 789615-002), Tenchlor tablets (786217-014 & 807591-017) and Tenoretic tablets (769568-009 & 769592-007).

General information

The combination of atenolol and chlorthalidone is a combination of beta-receptor blocker and a diuretic. Beta-receptor blockers are drugs prescribed for the treatment of high blood pressure, fast or irregular heart rhythms and to prevent chest pain (angina pectoris). Diuretics are drugs that increase the production of urine, thereby removing excess water from the body.

In South Africa this combination is registered for the treatment of mild to moderately high blood pressure.

This medication is not a cure for high blood pressure, but is effective in keeping it under control. For it to be effective you must take it regularly. High blood pressure declines slowly and it may take a few weeks for the combination of perindopril and indapamide to reach it full effect. Keep taking this medicine during this period, even if you are feeling better, or fail to notice any improvement.

Although atenolol is a cardio-selective beta blocker and is therefore less likely to affect the airways, it may still provoke breathing difficulties due to its effect on receptors in the lungs. If you suffer from asthma or other respiratory conditions, this combination should be taken with caution. You may also find strenuous activities more difficult, partly because of the drug’s effect on the lungs, and partly because it reduces heart rate.

Beta-blocking drugs may also reduce blood supply to the limbs and extremities and may therefore cause cold hand and feet. Some men may also experience temporary impotence when taking this combination as a result of reduced blood circulation.

Chlorthalidone enhances the excretion of potassium from your body and may warrant a potassium-rich diet (foods such as bananas or tomatoes), or even the use of a potassium supplement.

The first couple of doses of this medication may cause a sudden drop in blood pressure, which may cause dizziness or blackouts if you suddenly get up. It is therefore advised to be resting when starting treatment, and to lie down for 2 hours afterwards.

Because this medicine contains a diuretic, it should best be taken in the morning to prevent additional night-time visits to the toilet. It is possible that you may produce a larger volume of urine at the start of treatment with indapamide. Be aware of where your nearest ablution facilities are if you are away from home!

How does this combination work?

Atenolol reduces the force and speed at which the heart is beating. This assists in stabilising fast and abnormal heart rhythms, reduces blood pressure and decreases the heart's oxygen requirement which prevents angina.

A diuretic such as chlorthalidone reduces the overall fluid volume in the body, thereby reducing pressure within blood vessels.

Fast facts

Drug schedule: schedule 3

Available as: this combination is available as tablets.

What does it do? This combination lowers blood pressure and reduces the heart's workload.

Overdose risk: medium

Dependence risk: low

Is this combination available as a generic? yes

Is this combination available on prescription only? yes

User information

Onset of effect: although an effect may be seen much sooner, it may take several weeks for the maximum effect of this combination to be reached.

Duration of action: up to 24 hours

Dietary advice: chlorthalidone enhances the excretion of potassium from your body and may warrant a potassium-rich diet containing foods such as bananas or tomatoes.

Stopping this medicine: don't discontinue this combination without speaking to your doctor.

Suddenly stopping the drug may cause your blood pressure to increase dangerously, cause chest pain, and may cause fast or irregular hearth rhythms. A heart attack may even be provoked. When treatment with this medication needs to be stopped, the dosage should be gradually reduced under medical supervision.

Prolonged use: prolonged use may result in an electrolyte disturbance. Kidney function may also need to be evaluated periodically.

Special precautions

Consult your doctor before using this drug if:

  • you suffer from asthma or any other respiratory condition
  • you have or had severe congestive heart failure in the past
  • you have known liver or kidney disease
  • you have known low blood levels of potassium or high blood levels of calcium
  • you have gout
  • you have diabetes
  • you have been diagnosed with Addison's disease
  • you have been diagnosed with arteriosclerosis
  • you are taking any other medication

Pregnancy: avoid. Potential risk to the foetus has been reported. Consult your doctor before use, or if you are planning to fall pregnant.

Breastfeeding: avoid. This medication is passed through breast milk and may affect your baby adversely. Consult your doctor before use.

Porphyria: caution is advised.

Infants and children: safety and efficacy of this medication has not been established for children.

The elderly: caution is advised in the elderly as adverse effects may be more likely. A reduced dose may be needed.

Driving and hazardous work: caution is advised as use of this medication may lead to dizziness, light-headedness and/or sedation. Avoid such activities until you know how this medication affects you.

Alcohol: avoid concomitant use of alcohol with this medication as it may cause a dangerous drop in blood pressure.

Possible side effects



Side effects Frequency   Consult your doctor  
  Common Rare Only if severe In all cases
diarrhoea x   x  
dizziness/tiredness/weakness x   x  
headache x   x  
nausea/indigestion x   x  
muscle cramps or pain x   x  
thirst or dry mouth x   x  
visual disturbance   x x  
constipation   x x  
loss of appetite   x x  
erectile dysfunction   x x  
gout   x x  
increased blood sugar   x x  
palpitations   x   x
weakness   x   x
rash/itching   x   x
chest pain or tightness   x   x
difficulty breathing/swelling of the mouth/shortness of breath   x   x
swelling of ankles   x   x
jaundice   x   x




non-steroidal anti-inflammatory drugs (NSAIDs) e.g. ibuprofen May reduce the drugs hypertensive and diuretic effect/increase risk of kidney damage
other blood pressure medication risk of severe low blood pressure
certain drugs for malaria/malaria prevention risk of serious heart problems may be increased
cimetidine increased risk of atenolol toxicity
certain over-the-counter cold and flu remedies may risk of severe high blood pressure
corticosteroids may decrease atenolol's effectiveness
clonidine severe high blood pressure may occur
alcohol, barbiturates increased dizziness at start of treatment
allopurinol,tetracyclic antibiotics increased risk of cholrthalidone toxicity
cholestramine reducd absorption of chlorthalidone
corticosteroids reduced diuretic effect/risk of potassium depletion
digoxin increased risk of toxicity in case of potassium depletion
terfenadine, sotalol, pimozide risk of heart rhythm disturbance
lithium risk of litium toxicity
oral anti-diabetic drugs blood-sugar-lowering effect may be reduced
co-trimoxazole, trimethoprim reduced sodium levels in body
vitamin D increased risk of high calcium blood levels


Overdose action

A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention.

Recommended dosage

Adults: not to exceed dose as for each individual agent.



This material is not intended to substitute medical advice, but is for informational purposes only.   Please consult a physician for specific treatment and recommendations.



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