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Muscle cramps
Dr Asheesh Mehta Internal Medicine Specialist September 20, 2018
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Muscle cramps are a common but usually innocuous cause of severe pain in muscles, the pain lasting a few seconds to a few minutes. The cramp is a sudden spontaneous contraction of muscle. It is also known as a charley horse. Muscle cramps often occur at night and the muscles of the lower limbs, especially the calf, are the commonest site of spasm of muscle. They are most frequent when one is just going off to sleep or when waking up. Pain is often excruciating and the affected muscle may be felt as a tight contracted lump. Pain usually subsides in a short time but during the cramp it is generally not possible to use the involved muscle. The cramp may be due to spasm of part of the muscle or the entire muscle or even multiple muscles. In the latter case, it is most often muscles that act together to carry out a particular movement of a limb that contract together involuntarily. Muscle cramps may occur at any age, including in children, but are much commoner in older individuals.

Many conditions predispose to the occurrence of muscle cramps. Quite often muscle cramps occur after undertaking strenuous or unaccustomed exercise. The cramps may occur during exercise or a few hours afterwards, often when falling off to sleep. Muscle cramps are commoner in hot weather, especially when sweating is increased by unusual physical exertion. Dehydration from any cause too could precipitate muscle cramps. A reduction in blood levels of potassium, calcium or magnesium may also bring on muscle cramps. Pregnancy is also associated with more frequent muscle cramps and this is particularly so in the last few weeks of pregnancy. Although most of the times muscle cramps occur without serious or significant underlying medical problems, in a minority of cases muscle cramps may be due to such problems.

Muscle cramps are reported with use of many medications and this should be kept in mind as reducing the dose or substituting the offending medicine may provide lasting relief. Potentially severe underlying illnesses too need to be considered especially when muscle cramps are severe, atypical or associated with other symptoms or signs.

Many conditions predispose to the occurrence of muscle cramps. Quite often muscle cramps occur after undertaking strenuous or unaccustomed exercise
Among medicines, diuretics are one of the commonest types of drugs responsible for muscle cramps. Taking a diuretic causes one to pass more urine. They are indicated for a number of problems such as high blood pressure, heart failure, swelling in nephrotic syndrome, cirrhosis of liver, etc. The increased output of urine takes along with it electrolytes. Most diuretics cause an increased elimination of sodium and potassium while a few specific ones, termed potassium-sparing diuretics, allow the kidneys to retain potassium to a large degree. Loss of fluid as well as electrolytes such as potassium due to action of diuretics is what is believed to cause cramps in muscles. Muscle cramps may also occur with use of medicines used for diverse illnesses including asthma, myasthenia gravis, Parkinsonism, Alzheimer’s disease, etc. Women on oral contraceptives may also complain of muscle cramps.

Cramps occur in only a small proportion of patients using the medicines. Another relatively common problem is muscle cramps associated with use of statin drugs (brand names such as Lipitor and Crestor) used to control cholesterol levels in blood. Statins are among the largest selling drugs worldwide. The indications for these drugs have expanded quite a bit and if guidelines are strictly followed probably more than 10% of all adults will qualify for their prescription. Although they are among the safest of drugs quite a few patients taking them complain of muscle pain and cramps. These are more a nuisance than cause for concern. Reducing the dose may help in obtaining relief from the pain. The side effect is a class effect and is a risk with all statin molecules. Further, the higher the dose, the grater the chances of muscle pain and cramps. In spite of it being a class effect, changing the molecule does reduce complaints in some patients. In others the statin has to be withdrawn. Reintroduction at a lower dose after a few weeks may be much better tolerated. Their use is critical in people with heart attacks and those who have undergone procedures like angioplasty and these patients require statins in high doses. Reducing the dose or withdrawing the drug is fraught with significant risk in such patients. Effective alternatives to statins have been introduced recently but are very expensive and not widely available.

Muscle and nerve problems always need to be considered as causes of muscle cramps especially when they are prolonged, severe, occur with activity or are associated with alarm symptoms such as weakness or wasting of muscles. Muscle pain and cramps appearing in the legs on walking and being rapidly relieved on resting are characteristic of peripheral vascular disease. There is narrowing or blockage of arteries supplying blood to the lower limbs. Atherosclerosis in a somewhat similar manner to what takes place in coronary arteries where it causes ischaemic heart disease is the usual culprit. Smoking has a large contributory role in peripheral vascular disease. The symptoms are also quite analogous to those occurring in angina. Heart muscle requires more blood during exercise and when the coronary circulation is compromised, chest pain occurs. In peripheral vascular disease muscles of the legs suffer from inadequate circulation during exercise with occurrence of severe pain. In both conditions, symptoms are rapidly relieved by rest as circulation to the respective territories is still able to meet circulatory needs in resting conditions. Other muscle and nerve problems such as muscle injuries and peripheral neuropathy too may cause muscle cramps.

Quite a wide variety of systemic illnesses may at times be responsible for muscle cramps. In most such cases muscle cramps are not the sole symptoms. However, they may very well be the leading symptoms and it is important for the doctor to consider the possibility of underlying disease especially when muscle cramps are recent, atypical, severe or prolonged and when associated with other symptoms or signs. Hormonal diseases like hypothyroidism and Addison’s disease may be the cause. In the former there is a deficiency of thyroid hormones while in the latter there is a deficiency of adrenal gland hormones. Addison’s disease is readily overlooked in early stages. Severe metabolic disease such as liver failure due to cirrhosis as well as chronic kidney failure too may be associated with muscle cramps. Both conditions are notorious for causing nonspecific symptoms till disease is advanced. Investigations, however, readily establish the diagnosis.

Detailed investigations to determine the cause of muscle cramps are required in only a minority of patients in whom it is considered likely that an underlying significant illness is causing them. Basic investigations such as blood sugar and a complete blood count to detect diabetes and anaemia respectively are useful for screening purposes. A review of medications being taken is also indicated so that an offending drug may be substituted or withdrawn wherever possible. When significant illness is detected, specific treatment directed against it is indicated. In the majority of individuals with muscle cramps the history and examination is unrevealing of significant illness and measures to obtain relief from this generally innocuous but quite discomforting symptom needs to be considered. During the actual cramp, relief is often obtained by stretching and massaging the muscle. Holding the muscle in the stretched position till the cramp passes off is recommended. Both heat and cold applied locally are reported to provide benefit. Heat is generally useful for muscles that have become tight while cold may be useful for muscles which are tender to the touch. Magnesium pills are often promoted as being helpful to prevent muscle cramps. They may be useful in people having magnesium deficiency as the cause of the cramps. Even though magnesium is supposed to help relax muscles, it is not found to be too useful in other individuals with muscle cramps. Magnesium pills have also been used to prevent muscle cramps associated with pregnancy but with largely unconvincing results. Quinine which is a medicine used for malaria is quite effective in preventing muscle cramps. However, this is a potentially toxic medicine and most authorities recommend against using it for a condition that is relatively benign on the grounds that in this case the cure is worse than the illness. Selected muscle relaxants may offer some relief but there is a risk for them to be habit forming. Other drugs such as vitamin supplements, pain killers and calcium supplements are unlikely to be of any use in preventing muscle cramps.

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