My mother pasted this poem on my cupboard the day I was enrolled into medical college:
“Celebrated authors across the land
Wield the pen like a magic wand
But the words of greatest admiration
Are written by the hands writing a prescription”
I often look at it with a sigh and complain that medicine is a profession everybody practises and that there are a host of non-medical specialists who confidently volunteer to give their opinion. Initially I was intrigued as to why I received calls from parents asking if I was sure that they should give their child the medicine the way I have prescribed it. Friends call to double check on their pediatrician’s prescription. I now realise that parents behave in this way because children are so vulnerable to the effects of a medication error. Furthermore, children may not be able to recognize and communicate the initial signs and symptoms of a medication adverse effect.
After I received my degree, I pasted this alongside my mother’s words:
God and the Doctor they alike adore
But only when in danger, not before;
The danger o’er, both are alike requited,
God is forgotten, and the Doctor slighted.
I want to use this opportunity to explain what goes on in a good pediatrician’s mind while he prescribes – it is not an effortless process that is not thought through!
First, we prescribe a specific dose depending on the weight of the child. It is therefore possible for two kids of the same age to get slightly different doses. Drug dosage depends also on the formulation. For example, let us consider Paracetamol given for fever .Paracetamol drops come in a composition of 100mg per ml, a syrup of 125 mg per 5 ml, a double strength of 250 mg per 5ml and a tablet of 500 mg. So if a child of ten kilos needs a 10mg/kg dose of paracetamol she can be prescribed one ml of drops (or 12 drops), 5ml of syrup, 2.5 ml of a double strength syrup or one fourth of a tablet. It is always important to read the labels right (and be good at mathematics!).
Secondly, every drug is metabolized (broken down and acted upon by enzymes) by the body to an “active ingredient” .Effects of the drug become apparent when a certain amount of the active ingredient accumulates in the blood. This amount has a specific range which in medical terms is called “the therapeutic window”. An excess diverts the ingredient to be acted upon by several body rescue systems producing unwanted and sometimes toxic products, and a deficiency will produce no benefit. After that the compounds are predominantly cleared away by the liver and kidneys along with all other body waste. That is how a drug’s effect weans off and hence we write a twice or thrice daily schedule aiming to make the active ingredient available for longer periods of time. Paracetamol is extensively metabolized by the liver and it will be almost two hours before the effects are apparent. Over a period of four to six hours the effect wears out. This is why we insist that the drug be given no more than four times a day. There will be no additional benefit and it will become a toxic load for the immature liver to handle.