Debate On Single Versus Combination Drugs

There are thousands of drug formulations available both in the form of single-drug and combinations of two or more drugs in the market. The choice between them has long been a central issue in healthcare delivery and public health. Both type of formulations has advantages and limitations, and their rational use largely depends on disease pattern, patient history and healthcare facility. In Nepal, the healthcare system is constantly improving and this debate is more relevant in the light of drug affordability, rational use of drugs, and patient compliance issues. 

One active ingredient is present in a single-drug formulation and called monotherapy. To treat a condition, it has been a foundation of medical practice for a long time, as it is simpler to follow for a patient's outcome. The effectiveness, mechanism of action, and side effects of a monotherapy are easy to follow and in case of adverse events, identifying the responsible agent becomes easy. It helps in decision-making in clinical practice and in monitoring treatment courses and successes.  

Practicability

Another important advantage of single-drug therapy is the practicability in dosing. Often, the dose of a drug depends on the patient’s age, gender, weight, renal status, or disease severity, making it easy for a single-drug formulation to be adjusted accordingly. In managing chronic diseases such as diabetes, hypertension, epilepsy, or hormonal disorders, dose adjustment and individualisation of therapy are of paramount importance for better outcomes. For the rational use of drugs, monotherapy is the ideal prescribing practice in modern medicine. 

Despite its benefits, monotherapy has some limitations. In many chronic diseases and in some communicable diseases, a single drug may not be sufficient to achieve optimal effect. In conditions like HIV/AIDS, tuberculosis, certain cancers, and leprosy, monotherapy is often not sufficient in the management. Similarly, in managing hypertension and diabetes, a single drug may not be effective in all patients, which necessitates the addition of another drug.  

The combination drugs contain two or more active ingredients in a single formulation. The rationale is to enhance efficacy by targeting different mechanisms at the same time. In communicable disease management, such as in the case of tuberculosis, a fixed-dose combination proves better for preventing drug resistance and treatment success. Likewise, in cardiovascular diseases, instead of increasing the dose of a single agent, combining drugs with different mechanisms of action can provide better results in terms of managing blood pressure. 

Another important benefit of a fixed-dose combination is the improvement in patient compliance. It offers particular benefit to elderly patients and those with chronic illnesses requiring long-term treatment in comparison to taking multiple medications separately. Patient compliance is improved with the decrease in the number of drugs to be taken daily. In managing cardiovascular diseases, a combination of a diuretic with an antihypertensive agent is better to control blood pressure while minimising side effects, thus preventing toxicity. 

Dosage flexibility is restricted in a combination drug formulation in comparison to a single-drug formulation. It is often difficult to adjust the dose of one drug without affecting the others in a fixed-dose combination product. For example, if a patient suffers side effects due to one ingredient in a combination product, the entire treatment needs to be discontinued, particularly in patients needing individualised dosing.  

In many developing countries like Nepal, the market is flooded with fixed-dose combinations, which are irrational and oftentimes without scientific justification. These irrational combinations are products of overlapping mechanisms, unnecessary ingredients, or incompatible kinetics. Such formulations increase the risk of adverse events, contribute to polypharmacy, and increase healthcare costs without providing added therapeutic benefit. 

It is important to note that the safety and efficacy of combination drugs are often more complex. In such formulations, each component must be individually effective, and the combination must show added value. In countries like Nepal, the regulatory system is not strong enough to prevent substandard or irrational combinations flooding the market owing to insufficient manpower and weak scientific capabilities. 

Another important aspect that influences a provider’s choice is cost. In some cases, combination drugs may reduce overall treatment costs by enhancing compliance, but in other cases, treatment costs are significantly increased in comparison to single-drug therapy. In resource-poor settings, irrational combinations may cause unnecessary financial burden to families as most of the drug costs are from out-of-pocket expenditure. 

The healthcare system is overstretched and facing many challenges due to resource limitations, weak regulatory oversight, and rampant self-medication; thus, the debate of single versus combination drugs becomes more significant.  

Choice

The choice between single and combination drugs should be evidence-based, affordable, and judicious. Monotherapy should be utilised when a single agent suffices for the intended therapeutic goal, and at the same time, combination therapy should be reserved for cases where there are clear benefits in terms of safety, efficacy, or compliance. 

It has been seen that single and combination drug products have both benefits and limitations. In many uncomplicated cases, a single-drug formulation should be prescribed as it provides simple, flexible, and clear benefits, while combination drugs can be utilised for their enhanced efficacy and compliance in certain specific diseases. 

It is of paramount importance for healthcare providers to be judicious in selecting either product in order to ensure every prescription is rational, evidence-based, and individualised to the patient’s benefits. Thus, in an increasingly complex and overstretched healthcare landscape, particularly in developing economies, it is essential to maximize benefits to patients, and it is equally important to minimize risks and costs. 

(Dr. Lohani is the clinical director at the Nepal Poison Information Centre. lohanis@gmail.com)