Mallinckrodt's INOmax™ (Nitric Oxide) Gas, for Inhalation, Approved in Australia for Pulmonary Hypertension in Adults in Conjunction with Cardiovascular Surgery

-- Expands approved indication in Australia to include use of INOmax for perioperative pulmonary hypertension in conjunction with cardiovascular surgery in neonates through adults --

SYDNEY,April 11,2019 --Mallinckrodt plc (NYSE: MNK),a leading global specialty pharmaceutical company,today announced that INOmax™ (nitric oxide) gas,for inhalation has received regulatory approval in Australia by the Australian Therapeutic Goods Administration (TGA) for perioperative pulmonary hypertension in adults in conjunction with cardiovascular surgery. INOmax was previously approved for this same indication in neonates through adolescents up to age 17,and is also approved in Australia for the treatment of hypoxic respiratory failure (HRF) associated with pulmonary hypertension,a potentially life-threatening condition,in term and near-term newborns (>34 weeks).

INOmax nitric oxide is a vasodilator that opens (dilates) blood vessels,improving oxygen uptake and blood flow. It is used in conjunction with ventilator support and other appropriate agents. INOmax decreases pulmonary arterial pressure.

"This expanded approval of INOmax in Australia for cardiovascular surgery in adults is an important milestone for Mallinckrodt,confirming the benefit this therapeutic option can bring to perioperative pulmonary hypertension patients," said Steven Romano,M.D.,Executive Vice President and Chief Scientific Officer,Mallinckrodt. "We continue to focus on improving outcomes for underserved patients with severe and critical conditions,and this is an example of those efforts making a difference. There is a tremendous global need for therapies for patients undergoing cardiac surgery. We look forward to helping meet these needs."

ABOUT INOMAX

INOmax (nitric oxide) gas,for inhalation,is approved by the TGA in Australia for perioperative pulmonary hypertension in conjunction with cardiovascular surgery in neonates through adults,and for the treatment of HRF associated with pulmonary hypertension,a potentially life-threatening condition in newborns. It is approved in certain other countries for specified indications as well.

Before prescribing please refer to the full Product Information which is available from Mallinckrodt's Australian subsidiary by phone at 1300 198 565 or from this link.

Australia Minimum Product Information: INOmax (nitric oxide) gas,for inhalation

Indications: INOmax,in conjunction with ventilatory support and other appropriate agents,is indicated:

For the treatment of term and near-term (>34 weeks) neonates with hypoxic respiratory failure associated with clinical or echocardiographic evidence of pulmonary hypertension,in order to improve oxygenation and to reduce the need for extracorporeal membrane oxygenation.

To selectively decrease pulmonary arterial pressure in patients with perioperative pulmonary hypertension in conjunction with heart surgery.

Contraindications:Neonates known to be dependent on right-to-left or significant left-to-right shunting of blood; hypersensitivity to the active substance or any of the excipients.

Special Warnings and Precautions: Do not use INOmax undiluted; INOmax must be diluted by the ventilator gas flow to a concentration not greater than 20ppm; use an approved nitric oxide gas delivery system provided by the sponsor that meets the criteria specified in the Dosage and Administration Section. INOmax should not be discontinued abruptly,as it may result in rebound pulmonary hypertension syndrome; weaning should be performed with caution. Concentrations of methaemoglobin in the blood should be measured within one hour after initiation of INOmax therapy,using an analyser which can reliably distinguish between foetal haemoglobin and methaemoglobin; if methaemoglobin is >2.5%,the INOmax dose should be decreased and the administration of reducing agents may be considered. The dose of nitric oxide should be reduced if the concentration of nitrogen dioxide exceeds 0.5 ppm. The benefit/risk of using inhaled nitric oxide in patients with clinically significant left ventricular dysfunction should be evaluated on a case-by-case basis due to possible increased rate of serious adverse events. Treatment with inhaled nitric oxide might aggravate cardiac insufficiency in a situation with left-to-right shunting; prior to the administration of nitric oxide,pulmonary artery catheterisation or echocardiographic examination of central haemodynamics is recommended. Animal models have shown that nitric oxide may interact with haemostasis,resulting in an increased bleeding time.Long-term monitoring of babies post-treatment is recommended.

Use in pregnancy: Category B2.

Interactions with other medicines:Increased risk of methaemoglobinaemia with co-administration of nitric oxide donor compounds (e.g.,sodium nitroprusside,nitroglycerine) or drugs that increase methaemoglobinaemia(e.g.,prilocaine).

Adverse effects: Formation of methaemoglobin >5% has been observed. Rapid rebound reactions such as intensified pulmonary vasoconstriction and hypoxaemia after sudden withdrawal have been described,precipitating cardiopulmonary collapse. A clinical studyin neonates reported the following adverse effects with incidence of at least 5%: thrombocytopenia,hypotension,bacteraemia and/or local infection,rebound hypoxaemiaas very common (> 10% incidence) andatelectasis,haematuria,hyperglycaemia,hypokalaemia,hyperbilirubinaemia,stridor and cellulitis as common (1-10% incidence). No additional adverse events were identified in the paediatric cardiac surgery indication trials.

Dosage and Administration: INOmax should only be used after respiratory support is optimised including the use of surfactant in the neonatal intensive care unit setting,or only after conservative support has been optimised in the cardiac surgery setting. The maximum recommended dose of INOmax is 20 ppm. The delivery system must provide a constant inhaled INOmax concentration irrespective of the ventilator. As dosing is complex,refer to the full prescribing information for dosage,weaning,administration,and monitoring recommendations and methods.Prescribing information last amended 29 March 2019.

ABOUTMALLINCKRODT

Mallinckrodt is a global business consisting of multiple wholly owned subsidiaries that develop,manufacture,market and distribute specialty pharmaceutical products and therapies. The company's Specialty Brands reportable segment's areas of focus include autoimmune and rare diseases in specialty areas like neurology,rheumatology,nephrology,pulmonology and ophthalmology; immunotherapy and neonatal respiratory critical care therapies; and analgesics. Its Specialty Generics and Amitiza reportable segment includes specialty generic drugs,active pharmaceutical ingredients and AMITIZA® (lubiprostone). To learn more about Mallinckrodt,visit www.mallinckrodt.com.

Mallinckrodtuses its website as a channel of distribution of important company information,such as press releases,investor presentations and other financial information. It also uses its website to expedite public access to time-critical information regarding the company in advance of or in lieu of distributing a press release or a filing with theU.S. Securities and Exchange Commission(SEC) disclosing the same information. Therefore,investors should look to the Investor Relations page of the website for important and time-critical information. Visitors to the website can also register to receive automatic e-mail and other notifications alerting them when new information is made available on the Investor Relations page of the website.

Cautionary Statements Related to Forward-Looking Statements

This release includes forward-looking statements concerning INOmax. The statements are based on assumptions about many important factors,including the following,which could cause actual results to differ materially from those in the forward-looking statements: satisfaction of regulatory and other requirements; actions of regulatory bodies and other governmental authorities; changes in laws and regulations; issues with product quality,manufacturing or supply,or patient safety issues; and other risks identified and described in more detail in the "Risk Factors" section of Mallinckrodt's most recent Annual Report on Form 10-K and other filings with the SEC,all of which are available on its website. The forward-looking statements made herein speak only as of the date hereof and Mallinckrodt does not assume any obligation to update or revise any forward-looking statement,whether as a result of new information,future events and developments or otherwise,except as required by law.

CONTACTS

Media

Daniel Yunger

Kekst CNC

212-521-4879

mallinckrodt@kekstcnc.com

Investor Relations

Daniel J. Speciale,CPA

Vice President,Investor Relations and IRO

314-654-3638

daniel.speciale@mnk.com

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