Interesting, I guess I just never needed half a dose of anything. For Chantal though, it's like a raindrop in the ocean. She should be taking two pills twice a day at least.
You have a valid point. Some medications such as those used in pediatrics, cancer treatment, kidney disease, and anesthesia are in fact adjusted according to the weight or BMI of the patient. Antibiotics, however, usually are not. Some medical professionals argue that this is illogical and needs to change, but so far most practitioners give the same antibiotic dose to adults irrespective of weight.
As far as taking half a dose of medication, it often comes down to availabilty. In the hospital sometimes the doctor , for example, will order 300 mg of a medication, but the pharmacy only has 600 mg tablets on hand. When that happens (I'm a nurse), I use a pill splitter to cut the pill in half and administer the proper dose. It sometimes happens to outpatients, too. Half-pills will be given to patients in a blister pack (a card where you push the pill out) if the pharmacy doesn't have the correct dose.
Anytime I've been prescribed Azithromycin (Z-Pak) for bronchitis or a sinus infection, it's two pills a day (one in the morning, one in the evening) for five days. It's been a while but I don't remember them being giant yellow pills or being scored down the middle.
That's because Z-Paks usually contain 250 mg pills (at least in the U.S.). You take 2 the first day and 1 the next 4 days. Chantal was apparently given 500 mg pills, so she was instructed to take half that amount, i.e., 1 the first day, and half a pill the next 4 days. Or 1 pill for 3 days straight. They all equate to the same dosage, i.e., 1500 mg total.