Drug Therapy Problems – Causes | Classes | Consequences | Role of pharmacist

According to Paracelsus, a Swiss Physician, “All things are poison and nothing is without poison; only the dose makes a thing, not a poison.” This means that irrational or erroneous use of drugs can be very detrimental to health and one of the leading causes of morbidity and mortality associated with drug therapy problems (DTPs).



Nevertheless, irrational drug use can result from prescription errors, incorrect diagnosis, lack of proper information on drug use, and also errors associated with dispensing.


what is a drug therapy problem?

A Drug therapy problem is an undesirable event that is associated with drug use which interferes with the therapeutic outcome of the drug and the patient quality of life. In other words, it occurs as a result of prescription errors from the physician which are not addressed by the Pharmacist.

Therefore, spotting out and tackling DTPs is the soul of pharmaceutical care and should be the core objective of the Pharmacist. Notwithstanding, other healthcare teams have a big role to play in discovering and nullifying DTPs.

Causes of drug therapy problems

The causes of DTPs are multifactorial. Nevertheless, some factors that predispose patients to them include;

  1. Wrong prescription from the Physician or Prescriber
  2. Erroneous Dispensing of drugs by the Pharmacist.
  3. Misinterpretation of prescription
  4. Substandard counseling of patients about medication use.
  5. Inappropriate patient behavior (adherence/compliance)
  6. Patient idiosyncrasy i.e. Unmet drug-related needs of the patient such as untreated indications

The 8 classes of Drug therapy problems

Any of the following parameters listed below can lead to a drug therapy problem.


1. Unnecessary drug therapy

Unnecessary drug therapy is when a patient is given a drug that is not indicated for the medical problem being managed. Here, there is no rational judgment on the pharmacological action of the drug given. Besides, it is a waste of resources for the patient. For example, the Addition of cod-liver oil to an antimalarial drug.

2. Wrong Drug

This is a drug therapy problem that involves the use of the wrong drug to treat a medical problem. Most times this type of DTP occurs due to improper diagnosis or inadequate laboratory findings. In other words, improper diagnosis is the mainstay for treatment failures, waste of resources, and prolongation of stay in the hospital. For example, Giving antibiotics for a mite infection such as scabies.

3. Dosage too low (dose, frequency, duration)

It is a drug therapy problem characterized by the right drug given at a dose below the normal dose required by the patient to manage a disease condition. The frequency of dosing may also be low or the duration of the treatment.

In addition, It is important to know that the best way to titrate the right dose for a patient is the use of bodyweight rather than age. However, Another disease state of the patient is considered such as Kidney and Liver function.

Examples; An adult patient >40 kg receiving Ampicillin for Urinary tract infections

  • Dose too low ( Amoxicillin capsule 125 mg every 6 hours ).
  • Frequency too low ( Amoxicillin capsule 500 mg every 12 hours).
  • Duration too low (Amoxicillin capsule 500 mg every 6 hours x 3 days).

4. Dosage too high ( dose, frequency, duration)

The dosage of the drug administered in this case is higher than the therapeutic dosage required by the patient for that particular condition. It can be the dose, frequency, or duration.

Examples; An adult patient who is taking Ciprofloxacin for Salmonella typhi

  • Dose too high (Ciprofloxacin 1g every 12 hours x 7 days).
  • Frequency too high (Ciprofloxacin 500 mg every 8 hours x 7 days).
  • Duration too high (Ciprofloxacin 500 mg every 12 hours x 30 days ).

5. Adverse drug reactions (ADRs)

Adverse drug reaction (ADR) in response to a medicine that is noxious (harmful) and unintended and which occurs at doses normally used in man for the prophylaxis (prevention), diagnosis or therapy (treatment) of diseases, or for the modification of physiological function’. E.g., hypersensitivity reaction to Abacavir.

Therefore, an ADR is not predicted and does not occur as a result of carelessness. Rather, some patients have an idiosyncratic reaction toward a drug at its therapeutic dose.

Read more on Types, Causes, and Role of Pharmacist in the Prevention of  Adverse Drug Reactions;

6. Drug interactions (pharmaceutic, pharmacokinetic and pharmacodynamic)

Drug interaction is a medical outcome that results from the co-administration of more than one drug, a drug, and food or a drug administered in the presence of a disease that tends to alter the activity of the drug. The effect of the drug can increase, decrease, nullify or cause unwanted side effects.
Drug interactions can occur at Pharmaceutic, pharmacokinetic or pharmacodynamic levels.
(a) Mixing of Penicillin and aminoglycosides in the same serum bottle, which causes the formation of insoluble precipitates (Pharmaceutic)
(b) The inhibitory effect of Antacids on the Absorption of Tetracyclines ( Pharmacokinetic).
(c) Co-administration of glucocorticoids with hypoglycemic agents; the glucocorticoid neutralizes the hypoglycemic effects of antidiabetic drugs (Pharmacodynamics )

7. Inappropriate adherence

According to the World Health Organization, Adherence is the extent to which a person’s behavior – taking medication, following a diet, and/or executing lifestyle changes, corresponds with agreed recommendations from a health care provider.3

In other words, the patient is willing to be part of the decision-making and is responsible for executing the therapeutic plans recommended by the Health care Provider.

The consequence of non-adherence to medication is a therapeutic failure and worsening of the disease condition. A study has shown that 70% of patients admitted to the emergency department as a result of hypertensive Emergency or hypertensive urgency result from drug non-adherence.5

In summary, Adherence is as important as the drug given. Besides, You can take a horse to the dream but you cannot force yourself to drink water. However, Most issues with non-adherence result from improper counseling or not relating the patient’s need to its demographics such as social life. Therefore, the healthcare team must make sure that the patient is part of the decision-making process of the right drug and the Right route of administration.

8. Need for Additional drug therapy

Every drug in a Prescription must address a medical condition and every medical condition Should be in address for easy recovery of the patient. This type of Drug therapy problem occurs when there is a need to initiate extra therapy to address a condition previously neglected.

Meanwhile, most treatment without proper diagnosis is symptomatic. However, symptomatic treatment should be an adjunct to curative treatment. Therefore, It is a drug therapy problem if there is no drug addressing the underlying cause/etiology of the disease.

Consequences of drug therapy problems

  • Increased cost of therapy
  • There is a decline in the Patient’s quality of life.
  • Worsened health condition and length of stay in hospital.
  • Death cost
  • Reduced patient satisfaction

Role of a pharmacist in preventing drug therapy problems

A) Pharmacists should have a good communication approach when suggesting interventions in a drug therapy problem to the Physician.

B) Good Knowledge of the drug therapy problems and how to manage them is one of the core values of the good dispensing practice.

C) Maintaining a good Patient-Pharmacist relationship or Empathy will enable patients to be free to talk about their medical problems and challenges with adherence.

D) Community Pharmacists should make drugs cost-effective and easily accessible.

E) By being part of the multidisciplinary discussion at the stage of Ordering and prescription of drugs. Pharmacists can help discover drug therapy problems earlier before Prescribing the drugs.6

F) Proper counseling of patients on their disease condition and how to use their medication tends to reduce drug misuse and its consequences.

G) Strict follow-up and monitoring of the patient after discharge.

H) Drug interaction checker should be a tool in all pharmacy outlets to determine the drugs combination that may pose a risk to the patient.

I) Learning to give a test dose of drugs that can easily cause allergy before giving the full dose. E.g., Penicillins.


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