UNWANTED EFFECTS OF MORPHINE

by Dr Robert Twycross MA DM FRCP, Macmillan Clinical Reader in Palliative Medicine, University of Oxford
Dr Sylvia Lack, Consultant in Hospice Care, Waterbury, Connecticut

Doesn't morphine have a lot of unwanted effects?

The common unwanted effects seen with morphine therapy are:
At the beginning

• Vomiting
• Drowsiness
• Unsteadiness
• Confusion

Continuing

• Constipation

Occasional

• Dry mouth
• Sweating

Will I need medication to counteract nausea and vomiting?

If you vomit after taking your medication, the morphine will not be absorbed from the gut, the pain will continue, and you will lose confidence in the new medicine. To avoid this, some doctors recommend the routine use of an anti-vomiting drug when morphine is prescribed. Others prescribe for selected patients only.
You will certainly need to take an anti-vomiting drug if:

• You are already troubled by nausea and vomiting
• You are vomiting as a result of taking codeine or one of its alternatives
• You have vomited with morphine and similar drugs in the past.

You probably will not need an anti-vomiting drug if:

• You have no nausea and vomiting at the moment
• You have already taken codeine or another morphine-like drug regularly without nausea and vomiting

One-third of all patients prescribed morphine never need an anti-vomiting drug.

Will I have to go on taking the anti-vomiting drugs?

Vomiting with morphine is sometimes just an early unwanted effect. Your doctor may, therefore, reduce the dose of the anti-vomiting drug or phase it out altogether. This may be done after you have been on a steady dose of morphine for one to two weeks. If the nausea returns, this indicates that you need to stay on an anti-vomiting drug.

Will I get drowsy on morphine?

Like vomiting, drowsiness tends to be troublesome particularly during the first few days, possibly up to a week. It might come back again if the dose of morphine is increased. You should persevere in the knowledge that the drowsiness will lessen after a few days.

Occasionally, in the very old and frail, it is necessary to reduce the dose of morphine and then increase it again more slowly, every 2-3 days, until adequate pain relief is obtained.

Will I go on feeling drowsy or drugged?

Occasionally, yes. It is important to distinguish between persistent drowsiness and inactivity drowsiness. Most patients receiving morphine 'catnap' with ease. This means that you may drop off to sleep if sitting quietly and alone. This can be an advantage if you have limited stamina and require more rest and sleep than you did before you developed cancer. On the other hand, if your stamina is not greatly limited, you will find that you can live a relatively normal life.

If your work demands long hours at a desk, you may find you cannot concentrate for long and tend to sleep. If this happens, a trial of brain stimulant may be indicated. Other causes of drowsiness should, however, first be excluded by your doctor - particularly sedative drugs or certain sleeping tablets which take a long time to be cleared out of the body.

Will I get confused?

If you are over 70, you may become muddled at times during the first few days of treatment with morphine, but persevere - your mind will clear.

Will I get dizzy?

Again, those over 70 may experience dizziness or feel unsteady for a few days. You should continue with the morphine knowing that this unpleasant sensation will subside as your body adjusts to the morphine.

What about constipation?

This is the most troublesome unwanted effect of treatment with morphine and other strong pain-killers. It is important that you seek suitable advice from your doctor about laxatives and learn to manage your bowels effectively.
Do not stop taking the morphine even if controlling the constipation proves more difficult than controlling the pain.
Ask your doctor to prescribe an appropriate laxative when the morphine is started. Your doctor may prescribe both a softener and a stimulant laxative. These are available in combined as well as in separate preparations. The following should be noted:

• You do not need a bowel movement every day
• Aim for a bowel movement every second or third day; more is a bonus
• If you have no bowel movement for three days, use a suppository or arrange for an enema to be given by a nurse
• Drink plenty of fluids
• Prune juice can help in the mornings
• If you are eating well and have a good appetite, increase dietary fibre by adding bran to your breakfast cereal, or use a bulk laxative regularly every day
• If your appetite is poor, do not force yourself to eat fibre.

I find I've been sweating a lot since I started the morphine. Is this connected?

Yes, it may well be. Some patients complain of increased sweating after starting morphine. This can be heavy, and tends to be more marked at night. Sleep in thin nightclothes and in a cool room, with a change of clothes near at hand if the sweating is severe.

Sweating may be more troublesome if you also have a fever. If this is the case, aspirin or a similar drug is often helpful. You might like to discuss this with your doctor.

What happens if I cannot tolerate morphine?

In some patients, morphine slows down stomach emptying to such an extent that they feel nauseated and may vomit, despite the use of one of the commonly prescribed anti-vomiting drugs. In this case, a change to a drug that hastens stomach emptying is indicated. This usually sorts the problem out. If not, it will be necessary to change from morphine to one of its alternatives.

Very rarely, a patient taking morphine experiences hallucinations or has other disturbing psychological effects. Such feelings may pass off spontaneously, or settle with a suitable antidote.

Equally rarely, a patient complains of itching with oral morphine. If this happens, your doctor may well recommend a change to one of the alternatives to morphine.

It is important to emphasise that a change from morphine to one of its alternatives is rarely necessary. Used carefully and under supervision, oral morphine has an excellent track record.