What is an FDC?
When referring to drug treatment, the word FDC is an abbreviation of Fixed Dose Combination.
An FDC product is when 2 or more drugs are combined physically into one preparation such as a tablet or pill.
FDCs are useful in the treatment of diseases such as TB, HIV/AIDS & Malaria. In other circumstances there is widespread irrational use of FDCs. This is when drugs are combined in a way that is medically inappropriate and ineffective. At the beginning of the 1970s FDCs accounted for over half of the pharamaceutical products and for 40% of the best selling drugs in the USA.
Anti TB FDCs
Anti TB FDCs are usually a combination of two or more first line anti TB drugs. These are rifampicin, isoniazid, pyrazinamide and ethambutol. The reason for using FDCs for TB treatment comes from the fact that TB always requires multi drug therapy. The potential advantages associated with the use of FDCs are:
- Reduced risk of emergence of drug resistant strains:
- Less risk of medication errors:
- Better patient compliance:
- Reduced cost of treatment:
- Simplified drug supply management, shipping & distribution.
Prevention of drug resistance
Although multi drug therapy is prescribed for TB, in practice some patients select fewer or even only one drug. If they are only taking one drug this is described as monotherapy. The possible reasons for a patient taking fewer drugs include:
- A temporary lack of supply of one or more drugs:
- Mistakes in dispensing:
- A patient's deliberate decision to purchase only one drug to save money:
- A patient's deliberate decision to take only one drug because of perceived or real adverse effects associated with the other drugs.
Some patients taking fewer drugs and in some instances monotherapy, can result in those patients developing acquired drug resistance. This means that the drugs for the treatment of drug sensitive TB don't work. The patient then needs to take second line drugs which can be more difficult to take.
Initially "Combination packs" were introduced in an attempt to solve the problem of patients taking fewer drugs. These packs had all the pills to be taken at one time being packaged together so that the chance of a patient forgetting to take a pill was much reduced. But the patient could still choose not to take all the pills. As an FDC combines the most effective drugs in one formulation the use of FDCs makes it impossible for the patient to receive monotherapy.
Patients on FDC treatment need to take only 2 to 5 tablets per day according to their weight, in contrast to 9 to 16 tablets per day for those using separate formulations.
Schedule 9 and Schedule 10
In an Indian RNTCP 2015 document on the Daily Regimen in the Treatment of Drug Sensitive TB, it is said that the initial phase should consist of 2 months of Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), and Ethambutol (E). It is said that the RNTCP has retained the concept of "One Patient One Box" for the Daily Regimen. The daily regimen patient-wise box consists of blister packs of Schedule 9 (for Intensive Phase) and Schedule 10 (for Continuation Phase) packed in separate laminated pouches in a single milliboard/grey board box. The number of blister packs in each pouch will be according to the weight band
It is not clear where the phrases of Schedule 9 and Schedule 10 came from, and these phrases are not now used.