IMVANEX

Indications

• Measles
• Mumps
• Rubella
• Varicella (chickenpox)
• Yellow fever
• Rotavirus
• Intranasal influenza

Dosage

Children: Refer to the BNF for Children for specific dosing information based on age and vaccine type.

Adults: Refer to specific product guidelines for dosing information, as it can vary by vaccine type and brand.

Mechanism of action

Live vaccines work by introducing a weakened or attenuated form of a pathogen into the body. This stimulates the immune system to recognize and respond to the pathogen, leading to the production of antibodies and memory cells that provide long-term protection against future infections by the same pathogen.

Pharmacodynamics

The pharmacodynamics of live vaccines involve the activation of both humoral and cellular immunity. Following vaccination, the immune system generates a robust response, including the production of specific antibodies and the activation of T cells that can recognize and eliminate infected cells. This dual action helps establish long-term immunity.

Pharmacokinetics

The pharmacokinetics of live vaccines vary depending on the specific vaccine. Generally, the vaccine is administered via injection, allowing the live attenuated organisms to enter the bloodstream. The immune response typically begins within days and can last for years, depending on the vaccine. Live vaccines are usually stored under refrigeration to maintain their viability, and they should be administered within their expiration dates.

Interactions

• livevaccines + abrocitinib: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + baricitinib: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + filgotinib: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + dexrazoxane: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + iron chelators: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + ozanimod: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + ponesimod: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + siponimod: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + upadacitinib: Severe (increases risk of generalised infection (possibly life-threatening))
• livevaccines + diroximelfumarate: Moderate (increases risk of generalised infection (possibly life-threatening))

Dosage

Children: Paediatric dosing for modified drugs must be derived from established guidelines or clinical recommendations. Consult the relevant guidelines or formulary for age-appropriate dosing.

Adults: Dosing for modified drugs is highly specific to each agent and should be determined based on clinical guidelines and individual patient needs. It is essential to refer to specific product literature or a professional drug reference for accurate dosing information.

Mechanism of action

The mechanism of action for modified drugs varies significantly depending on their specific structure and target. Generally, modifications can enhance binding affinity to receptors, alter metabolic pathways, or improve cellular uptake. For example, modifications may lead to increased selectivity for target enzymes or receptors, thereby improving therapeutic outcomes and reducing off-target effects.

Pharmacodynamics

Pharmacodynamics of modified drugs typically includes alterations in the drug's potency and efficacy, influenced by the structural changes made. These modifications can lead to improved therapeutic indices by enhancing the desired pharmacological effect while minimizing adverse effects. Such changes may also affect receptor activation, signal transduction pathways, and downstream physiological effects.

Pharmacokinetics

The pharmacokinetics of modified drugs can be significantly altered based on the nature of the modifications. Factors such as absorption, distribution, metabolism, and excretion (ADME) can be optimized to improve bioavailability and half-life. For instance, modifications might enhance solubility, stability, or resistance to enzymatic degradation, affecting how the drug is processed in the body.

Indications

• Prevention of smallpox
• Post-exposure prophylaxis in smallpox outbreaks
• Research purposes in vaccine development

Dosage

Children: Vaccinia is not typically administered to children under 1 year of age. For specific paediatric dosing, refer to

Adults: Vaccinia is administered as a single dose via intradermal injection, using a bifurcated needle. Specific dosing information should be referred to in official guidelines and product inserts.

Mechanism of action

Vaccinia induces an immune response that provides cross-protection against variola virus, the causative agent of smallpox. The virus replicates in the host cells, leading to the production of viral proteins that stimulate both humoral and cellular immunity. This immune response includes the generation of neutralizing antibodies and the activation of T-cells, which together help to provide protection against future infections with smallpox.

Pharmacodynamics

The pharmacodynamics of vaccinia involves the activation of innate and adaptive immune responses. After vaccination, the body produces specific antibodies against the vaccinia virus, which also cross-react with the smallpox virus. The cellular immune response includes the activation of T-helper cells and cytotoxic T lymphocytes, which are crucial for the elimination of the virus. The duration of immunity can vary, typically lasting several years, with some individuals maintaining protection for decades.

Pharmacokinetics

Vaccinia is administered through vaccination, primarily via a bifurcated needle that delivers the virus intradermally. The absorption occurs at the site of inoculation, leading to localized infection and immune response. The half-life of the virus within the body is not well defined due to its live attenuated nature, but the immune response is initiated within days of vaccination, with complete seroconversion typically occurring within 2-4 weeks. The virus is not cleared in the traditional sense as it is designed to stimulate the immune system rather than cause disease.

Contra-indications

• Severe allergic reaction to the vaccine or any component of the vaccine
• Immunocompromised individuals
• Pregnant women
• Individuals with eczema or atopic dermatitis

Adverse effects

• Injection site reactions (redness, swelling, pain)
• Fever
• Fatigue
• Rash
• Myocarditis
• Encephalitis
• Secondary spread of the vaccine virus

Interactions

• Immunosuppressive therapies may reduce the efficacy of the vaccine
• Live vaccines should generally not be administered concurrently

Precautions

• Individuals with a history of eczema or skin conditions
• Those with a family history of immunodeficiency
• Avoid contact with immunocompromised individuals after vaccination

Pregnancy

Vaccination is contraindicated in pregnant women due to potential risks to the fetus.

Breast-feeding

Caution is advised; consult healthcare providers regarding vaccination while breastfeeding.

Storage

Store in a refrigerator (2-8 degrees Celsius), protect from light. Do not freeze.

Formulations

• Live vaccinia virus vaccine

Indications

• Influenza
• HIV/AIDS
• Hepatitis B and C
• Herpes simplex virus infections
• Cytomegalovirus infections
• COVID-19
• Respiratory syncytial virus infections

Dosage

Children: Refer to specific antiviral agents for dosing guidance.

Adults: Refer to specific antiviral agents for dosing guidance.

Mechanism of action

Viruses infect host cells by attaching to specific receptors on the cell surface. Once inside, they hijack the host cell's machinery to replicate their genetic material and produce viral proteins. New viral particles are assembled and released from the host cell, often destroying the cell in the process. The specific mechanism can vary depending on the virus type, including integration into the host genome in retroviruses or utilizing specific pathways for replication.

Pharmacodynamics

The pharmacodynamics of antiviral agents depend on the specific virus and the mechanism of action. Antiviral drugs may inhibit viral entry into host cells, block viral replication, or prevent the assembly of new virions. The effectiveness of antiviral therapy often relates to the stage of viral replication and the immune response of the host.

Pharmacokinetics

Pharmacokinetics of antiviral drugs varies widely based on the specific medication used. Generally, antiviral agents are absorbed through the gastrointestinal tract and distributed throughout the body. They may undergo hepatic metabolism and are often excreted through the kidneys. The half-life of these drugs can range from a few hours to several days, influencing dosing schedules.