Topotecan - Uses, Dosage, and Side Effects

What Is Topotecan?

Topotecan injection is a medicine that is used to treat cancer that has spread to other parts of the body. It is specifically given for ovarian cancer when other treatments do not work as per the expectations. It is also used for a type of lung cancer called small-cell lung cancer. When combined with Cisplatin, it is used to treat cervical cancer that has come back and cannot be treated with surgery or radiation.

Topotecan is an anticancer medicine. It actually works by slowing down or stopping the growth of cancer cells. This helps kill the cancer cells over time. It can also affect some healthy cells. Because of this, a few side effects may occur. Some side effects can be serious and need medical attention. Others, like hair loss, are not dangerous but can be upsetting.

When Was Topotecan Approved?

The medication was approved by the U.S. Food and Drug Administration in 1990 after Phase II clinical trials. Later, in 1996, it was approved for the treatment of ovarian cancer and small-cell lung cancer. Topotecan is a very special drug because it is the first oral topoisomerase-I inhibitor that has been used in cancer treatment.

How Does Topotecan Work?

The drug is a topoisomerase inhibitor that blocks topoisomerase 1. This chemical is important in DNA (deoxyribonucleic acid) replication and transcription. In addition, it alters the chromosome structure by changing the topological state of DNA. They can also relax supercoiled DNA and interlock DNA. Blocking this is extremely important to prevent the proliferation of cancerous cells.

Cancerous cells affect the immune system and attack the healthy cells of the body. This, in turn, leads to optimistic infections. Diagnosing cancer early is a boon to the patient, as the treatments are very effective and bring positive outcomes. Topotecan is used explicitly in the treatment of small-cell lung cancer.

Uses:

• It is used in patients with metastatic cancer. It spreads from one part to other body parts.

• The drug is used with Cisplatin for cervical cancer.

• It is also effective in small-cell lung cancer.

Dosage:

• The drug is available as oral medicine and as an injection. The injection is given through a vein.

• The doctor decides the best method of treatment.

• This depends on the severity of lung cancer.

• The drug comes in different doses.

• The dose is determined by the patient’s weight.

Warnings:

• Bone Marrow: Topotecan can cause a strong suppression of the bone marrow, which is the most serious side effect of the drug. This results in low white blood cell, platelet, and red blood cell counts.

• Low-white Blood Cell Count: This can lead to serious infections, and in some cases, these infections may be life-threatening. Low platelets may cause bleeding, and low red blood cells may cause anemia. Treatment should only be initiated or continued when the blood counts are safe.

• Neutropenic Colitis: Topotecan may decrease the number of white blood cells in the body, which can lead to a serious infection of the bowel called neutropenic colitis. Neutropenic colitis is potentially life-threatening and has been fatal in some patients. When fever, low white blood cell count, and abdominal pain occur together, neutropenic colitis should be considered.

• Interstitial Lung Disease: Topotecan can cause lung injury, also known as interstitial lung disease. In some cases, the disease has been severe and even life-threatening. The symptoms of this disease include cough, fever, shortness of breath, or low oxygen levels, and the treatment should be discontinued if lung disease is confirmed.

• Embryofetal Toxicity: Topotecan can cause serious harm to the unborn baby if taken during pregnancy. Animal studies have revealed fetal death and congenital anomalies with the use of this drug. Pregnant patients or those who become pregnant should be warned about the risks.

For Patients

How Effective Is Topotecan?

The Topotecan has been proven to be highly effective in treating small-cell lung cancer and is useful when used in combination with a few other anti-cancer drugs.

Things to Inform the Doctor Before They Prescribe Topotecan:

• Inform the doctor regarding any previous drug allergies and current medical and drug history. This helps to avoid drug interactions and overdosing. Carry a copy of the prescription while visiting the doctor; this helps them better evaluate their health status.

• Before starting any drug, it is always essential to understand the risks of the medication over the positive outcomes. The doctor will analyze the patient’s health condition and prescribe medications to treat cancer and prevent a recurrence. Hence, patient cooperation is a crucial factor in the success of the treatment.

How to Take Topotecan?

Topotecan can be administered intravenously or in the form of oral capsules that have to be taken after food, as prescribed by the doctor.

Look Out for Side Effects:

In case of the following side effects, inform the health care professional.

• Bleeding gums.

• Black stools.

• Body aches.

• Pain.

• Chest pain.

• Chills.

• Congestion (Blocked or stuffy nose).

• Cough.

• Sore throat.

• Fever.

• Lower back pain.

• Difficult urination.

• Pale skin.

• Sneezing.

• Trouble swallowing.

• Fatigue or tiredness.

• Changes in voice.

• Spots in the mouth.

Some of the other less common effects, while consuming Topotecan, are,

• Confusion.

• Diarrhea.

• Dizziness.

• Fainting.

• Fast heartbeat.

• Lightheadedness.

• Nausea.

• Pain in the abdomen.

• Shallow breathing.

• Stomach pain.

• Vomiting.

Dietary Alterations:

No specific dietary alterations are required in patients consuming Topotecan. Unless suggested by the doctor, a regular diet would suffice. Maintaining a healthy and balanced diet is crucial while consuming medications. It helps to absorb the medications and keeps the body nourished. Poor nutrition can have adverse effects on an individual's overall health.

What Should Be Done When a Dose Is Missed?

• If a dose of Topotecan is missed when taken orally, take it as soon as possible.

• If the next dose is almost due, skip the missed dose.

• Continue with the regular dosing schedule.

• Do not take extra doses to make up for the missed dose.

• Do not miss doses often, as this can slow down recovery.

What Should Be Done to Treat Topotecan Overdose?

• Topotecan oral capsules should only be taken as directed by the doctor.

• Taking a higher dose can harm healthy cells. This can cause side effects.

• If there is an overdose, a healthcare professional should be contacted immediately.

• An overdose of Topotecan injection is rare. The injection is administered in a hospital setting. The dose is carefully watched by the doctor.

• If there is an overdose, the injection should be stopped immediately.

How to Store Topotecan?

The drug is available in the form of intravenous injections and oral capsules. Hence, it has to be stored in a cold and dry place. Do not keep it reachable to children or pets, as it could be dangerous.

How to Handle Topotecan?

• Always use gloves while consuming oral capsules to avoid contamination.

• Keep the bottle tightly sealed after taking the required medication.

• Do not keep it near children or pets.

• Always check the label of the box for expiry. Do not consume any drug post-expiration.

How to Dispose of Topotecan?

It is always safer to contact the local take-back programs to dispose of the drugs and avoid any biohazards. Do not flush the drug in the toilet or the dustbin. It is better to keep them separate and dispose of them via medical waste management.

Avoid Self-Medication:

Never consume any drug more than the required dosage, as it causes ill effects. Self-medication is extremely harmful and hence has to be avoided in any circumstance. Always take a doctor’s consultation before taking medication.

For Doctors

Pharmacology:

Mechanism of Action: The drug is a derivative of Camptothecin and a topoisomerase inhibitor that prevents the re-ligation of the cleaved DNA strand and subsequently causes DNA damage. Inactivation of topoisomerase could cause apoptosis and cell death. The drug binds to the topoisomerase 1 DNA complex and breaks it into single strands. This interferes with the replicating fork, leading to induction and replication arrest, breaking the lethal double-stranded DNA.

Taxonomy:

• Kingdom - Organic compounds.

• Subkingdom - Organic oxygen compounds.

• Superclass - Organic heterocyclic compounds.

• Class - Indoles and derivatives.

• Subclass - Indolines.

• Direct Parent - Campththecins.

• Molecular Formula - C23H23N3O5.

Pharmacodynamics: Topotecan is an anticancer agent and a novel semisynthetic derivative of the anticancer agent Camptothecin. The lactone structure helps maintain the equilibrium with the inactive ring of hydroxy acid. This is an essential activity and predominates at physiological pH (power of hydrogen).

Pharmacokinetics

It has a bioavailability of 35 percent when taken orally because of the degradation of its active compound in the intestines. It is widely distributed in the body, and its volume of distribution is large. The drug is present in its active lactone form and its inactive hydroxy-acid form, depending on the body's pH. It is primarily excreted in the kidneys, and its average half-life is three hours. The kidneys play an important role in the elimination of the drug from the body.

Ingredients:

Active Ingredients:

The drug consists of an active substance called Topotecan, a Camptothecin derivative, that is produced from the tree Camptotheca acuminata. The nuclear enzyme helps relieve the torsional strain in DNA and helps to break it into single-stranded DNA.

Inactive Ingredients:

Some of the inactive ingredients in Topotecan are mentioned below:

• Mannitol.

• Tartaric acid.

• Hydrochloric acid.

• Sodium hydroxide.

Absorption:

The bioavailability of the drug in oral form is roughly about 35 percent. Lower bioavailability is caused by the hydrolysis action of Topotecan lactone, present in the gut. It yields substantial amounts of the open-ring form, which could cause poor absorption.

Distribution:

The drug has a wide distribution in the peripheral space. It makes up a total volume of about 75 liters at the steady state of the drug.

Metabolism:

The drug undergoes reversible pH-dependent hydrolysis. The lactone form of the drug is pharmacologically active. At acidic pH, the drug is exclusively available. In the ring-opened form, hydroxy-acid predominates the condition.

Elimination:

The mean elimination of the drug is roughly three hours. The renal clearance accounts for about 40 percent of the dose and has a large interindividual variability. The drug is eliminated via the kidneys after it undergoes filtration.

Toxicity:

Drug toxicity may result in the following medical conditions:

• Bone marrow suppression.

• Anemia.

• Thrombocytopenia.

• Pancytopenia.

The dose-limiting toxicity is observed in many individuals, approximately 50 to 75 percent in clinical trials.

Contraindications

The drug is an absolute contraindication in patients with a history of hypersensitivity or allergic reactions.

Drug Interactions:

While undergoing Topotecan injection, it is better to avoid the following drugs, as they may cause drug interactions:

• Measles live vaccine.

• Mumps live vaccine.

• Rotavirus live vaccine.

• Zoster vaccine.

• Varicella virus vaccine.

Other Specifications:

• Topotecan in Pregnant Women: The drug’s efficiency in pregnant women is not known completely; it is not prescribed in pregnant women as it could cross the placenta and affect the unborn child, resulting in birth deformities.

• Topotecan in Lactating Women: Studies are being conducted to understand the drug's efficacy in pregnant women. Most studies have yet to prove the exact side effects and potential risks the drug could cause in breastfeeding women. Hence, it is not currently prescribed for lactating women.

• Topotecan in Pediatric Patients: The drug is not usually advised in pediatric patients. There are very few supporting studies regarding drug usage in children.

• Topotecan in Geriatric Patients: The drug could be harsh on elderly individuals, especially those with kidney impairment. Hence, it is important to carefully administer Topotecan injections in elderly individuals after weighing the potential risks and complications.

• Topotecan in Renal Impairment Patients: In patients with kidney impairment, the drug could aggravate the impairment; it should be carefully administered and followed up regularly to monitor the prognosis of the lung cancer.

• Topotecan in Hepatic Impairment Patients: Although there have not been any relative complications in patients with hepatic impairment, it has to be used with caution to avoid any complications.