Guide to Good Prescribing - A Practical Manual
(1994; 115 pages) [Arabic] [Bengali; Bangla] [French] [Korean] [Romanian] [Russian] [Spanish] View the PDF document
Table of Contents
View the documentAcknowledgments
View the documentWhy you need this book
Open this folder and view contentsPart 1: Overview
Open this folder and view contentsPart 2: Selecting your P(ersonal) drugs
Close this folderPart 3: Treating your patients
View the documentChapter 6. STEP 1: Define the patient's problem
View the documentChapter 7. STEP 2: Specify the therapeutic objective
Close this folderChapter 8. STEP 3: Verify the suitability of your P-drug
View the documentStep 3A: Are the active substance and dosage form suitable for this patient?
View the documentStep 3B: Is the standard dosage schedule suitable for this patient?
View the documentStep 3C: Is the standard duration of treatment suitable for this patient?
View the documentChapter 9. STEP 4: Write a prescription
View the documentChapter 10. STEP 5: Give information, instructions and warnings
View the documentChapter 11. STEP 6: Monitor (and stop?) the treatment
Open this folder and view contentsPart 4: Keeping up-to-date
Open this folder and view contentsAnnexes
View the documentBack Cover

Step 3C: Is the standard duration of treatment suitable for this patient?

Many doctors not only prescribe too much of a drug for too long, but also frequently too little of a drug for too short a period. In one study about 10% of patients on benzodiazepines received them for a year or longer. Another study showed that 16% of outpatients with cancer still suffered from pain because doctors were afraid to prescribe morphine for a long period. They mistook tolerance for addiction. The duration of the treatment and the quantity of drugs prescribed should also be effective and safe for the individual patient.

Overprescribing leads to many undesired effects. The patient receives unnecessary treatment, or drugs may lose some of their potency. Unnecessary side effects may occur. The quantity available may enable the patient to overdose. Drug dependence and addiction may occur. Some reconstituted drugs, such as eye drops and antibiotic syrups, may become contaminated. It may be very inconvenient for the patient to take so many drugs. Last, but not least, valuable and often scarce resources are wasted.

Underprescribing is also serious. The treatment is not effective, and more aggressive or expensive treatment may be needed later. Prophylaxis may be ineffective, resulting in serious disease, e.g. malaria. Most patients will find it inconvenient to return for further treatment. Money spent on ineffective treatment is money wasted.

Exercise: patients 21-28

For each of the following cases verify whether the duration of treatment and total quantity of the drugs are suitable (effective, safe). In all cases you may assume that the drugs are your P-drugs.

Patient 21:

Woman, 56 years. Newly diagnosed depression. R/amitriptyline 25 mg, one tablet daily at night, give 30 tablets.

Patient 22:

Child, 6 years. Giardiasis with persistent diarrhoea. R/metronidazole 200 mg/5 ml oral suspension, 5 ml three times daily, give 105 ml.

Patient 23:

Man, 18 years. Dry cough after a cold. R/codeine 30 mg, 1 tablet three times daily, give 60 tablets.

Patient 24:

Woman, 62 years. Angina pectoris, waiting for referral to a specialist. R/glyceryl trinitrate 5 mg, as necessary 1 tablet sublingual, give 60 tablets.

Patient 25:

Man, 44 years. Sleeplessness. Comes for a refill, R/diazepam 5 mg, 1 tablet before sleeping, give 60 tablets.

Patient 26:

Girl, 15 years. Needs malaria prophylaxis for a two week trip to Ghana. R/mefloquine 250 mg, 1 tablet weekly, give 7 tablets; start one week before departure and continue four weeks after return.

Patient 27:

Boy, 14 years. Acute conjunctivitis. R/tetracycline 0.5% eye drops, first 3 days every hour 1 drop, then 2 drops every six hours, give 10 ml.

Patient 28:

Woman, 24 years. Feels weak and looks a bit anaemic. No Hb result available. R/ferrous sulfate 60 mg tablets, 1 tablet three times daily, give 30 tablets.

Patient 21 (depression)

A dose of 25 mg per day is probably insufficient to treat her depression. Although she can start with such a low dose for a few days or a week, mainly to get used to side effects of the drug, she may finally need 100-150 mg per day. With 30 tablets the quantity is sufficient for one month, if the dosage is not changed before that time. But is it safe? At the beginning of the treatment the effect and side effects cannot be foreseen. And if the treatment has to be stopped, the remaining drugs are wasted. The risk of suicide also has to be considered: depressive patients are more liable to commit suicide in the initial stages of treatment when they become more active because of the drug, but still feel depressed. For these reasons 30 tablets are not suitable. It would be better to start with 10 tablets, for the first week or so. If she reacts well you should increase the dose.

Patient 22 (giardiasis)

With most infections time is needed to kill the microbes, and short treatments may not be effective. However, after prolonged treatment the micro-organisms may develop resistance and more side effects will occur. In this patient the treatment is both effective and safe. Giardiasis with persistent diarrhoea needs to be treated for one week, and 105 ml is exactly enough for that period. Maybe it is even too exact. Most pharmacists do not want to dispense quantities such as 105 ml or 49 tablets. They prefer rounded figures, such as 100 ml or 50 tablets, because calculating is easier and drugs are usually stocked or packed in such quantities.

Patient 23 (dry cough)

The quantity of tablets is much too high for this patient. The persistent dry cough prevents healing of the irritated bronchial tissue. Since tissue can regenerate within three days the cough needs to be suppressed for five days at most, so 10-15 tablets will be sufficient. Although a larger quantity will not harm the patient, it is unnecessary, inconvenient and needlessly expensive. Many prescribers would argue that no drug is needed at all (see p.8).

Patient 24 (angina)

For this patient the quantity is excessive. She will not use 60 tablets before her appointment with the specialist. And did you remember that the drug is volatile? After some time the remaining tablets will no longer be effective.

Patient 25 (sleeplessness)

The diazepam refill for patient 25 is worrying. You suddenly remember that he came for a similar refill recently and check the medical record. It was two weeks ago! Looking more closely you find that he has used diazepam four times daily for the last three years. This treatment has been expensive, probably ineffective and has resulted in a severe dependency. You should talk to the patient at the next visit and discuss with him how he can gradually come off the drug.

Box 6: Repeat prescriptions in practice

In long-term treatment, patient adherence to treatment can be a problem. Often the patient stops taking the drug when the symptoms have disappeared or if side effects occur. For patients with chronic conditions repeat prescriptions are often prepared by the receptionist or assistant and just signed by the physician. This may be convenient for doctor and patient but it has certain risks, as the process of renewal becomes a routine, rather than a conscious act. Automatic refills are one of the main reasons for overprescribing in industrialized countries, especially in chronic conditions. When patients live far away, convenience may lead to prescriptions for longer periods. This may also result in over prescribing. You should see your patients on long-term treatment at least four times per year.

Patient 26 (malaria prophylaxis)

There is nothing wrong with this prescription which follows the WHO guidelines on malaria prophylaxis for travellers to Ghana. The dosage schedule is correct, and she received enough tablets for the trip plus four weeks afterwards. Apart from a small risk of drug resistance this drug treatment is effective and safe.

Patient 27 (acute conjunctivitis)

The prescription of 10 ml eyedrops seems adequate, at first sight. In fact, eyedrops are usually prescribed in bottles of 10 ml. But did you ever check how many drops there are in a bottle of 10 ml? One ml is about 20 drops, so 10 ml is about 200 drops. One drop every hour for the first three days means 3 x 24 = 72 drops. That leaves about 128 drops in the bottle. Two drops four times per day for the remaining period is 8 drops a day. That is for another 130/8 = 16 days. The total treatment therefore covers 3 + 16 = 19 days! Yet, seven days treatment at most should be enough for bacterial conjunctivitis. After some arithmetic (72 + (4 x 8) = 104 drops = 104 x 0.05 = 5.2 ml) you conclude that 5 ml will be enough in future. This will also prevent any leftovers from being used again without a proper diagnosis. Even more important, eyedrops become contaminated after a few weeks, especially if they are not kept cool, and can cause severe eye infections.

Patient 28 (weakness)

Did you notice that this is a typical example of a prescription without a clear therapeutic objective? If the diagnosis is uncertain, the Hb should be measured. If the patient is really anaemic she will need much more iron than the ten days given here. She will probably need treatment for several weeks or months, with regular Hb measurements in between.


Verifying whether your P-drug is also suitable for the individual patient in front of you is probably the most important step in the process of rational prescribing. It also applies if you are working in an environment in which essential drugs lists, formularies and treatment guidelines exist. In daily practice, adapting the dosage schedule to the individual patient is probably the most common change that you will make.


STEP 3: Verify that your P-drug is suitable for this patient


Are the active substance and dosage form suitable?


Indication (drug really needed)?

Convenience (easy to handle, cost)?


Contraindications (high risk groups, other diseases)?

Interactions (drugs, food, alcohol)?


Is the dosage schedule suitable?


Adequate dosage (curve within window)?

Convenience (easy to memorize, easy to do)?


Contraindications (high risk groups, other diseases)?

Interactions (drugs, food, alcohol)?


Is the duration suitable?


Adequate duration (infections, prophylaxis, lead time)?

Convenience (easy to store, cost)?


Contraindications (side effects, dependence, suicide)?

Quantity too large (loss of quality, use of leftovers)?

If necessary, change the dosage form, the dosage schedule or the duration of treatment.

In some cases it is better to change to another P-drug.

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