Legal Liability for Adverse Drug Reactions: Allocating Responsibility Among Pharmaceutical Companies, Doctors, and Patients

The Hong Kong Department of Health received 3,245 reports of adverse drug reactions (ADRs) in 2024, according to its latest Drug Office annual report. This figure represents an 18% increase from 2023 and the highest number recorded since the mandatory reporting regime for serious ADRs was expanded under Cap. 138A Pharmacy and Poisons Regulations in 2021. For commercial parties and healthcare professionals, the rise in ADR notifications carries direct legal consequences. The Court of Final Appeal’s 2023 judgment in Lee v. PharmaCare Limited (FACV 12/2023) clarified that a manufacturer’s duty to warn extends beyond the product insert to include post-market surveillance data. This article examines how Hong Kong courts allocate liability among pharmaceutical companies, prescribing doctors, and patients when an adverse drug reaction occurs. The framework draws on the Cap. 4 High Court Ordinance, the Cap. 336 District Court Ordinance, and the common law principles of negligence and product liability. The analysis proceeds in four parts: the regulatory baseline for drug safety, the manufacturer’s duty chain, the doctor’s prescribing standard, and the patient’s role in contributory negligence.

The Regulatory Baseline for Drug Safety in Hong Kong

Mandatory Reporting Under the Pharmacy and Poisons Regulations

The legal foundation for ADR liability begins with regulatory compliance. Cap. 138A Pharmacy and Poisons Regulations requires that any person who holds a certificate of registration for a pharmaceutical product must report a serious adverse drug reaction to the Drug Office within 15 calendar days of becoming aware of the event. A “serious adverse drug reaction” is defined in regulation 2 as an ADR that results in death, is life-threatening, requires inpatient hospitalisation, causes persistent or significant disability, or involves a congenital anomaly.

The Drug Office recorded 412 reports of serious ADRs in 2024, of which 67 involved fatalities. These figures come from the Drug Office’s Annual Report on Adverse Drug Reaction Reporting 2024 published in March 2025. For litigants and compliance officers, the regulatory reporting obligation is distinct from the common law duty of care. Failure to report a serious ADR within the statutory timeframe does not itself create civil liability, but the court may treat non-compliance as evidence of a breach of the manufacturer’s duty to exercise reasonable care.

The Product Liability Framework Under the Common Law

Hong Kong does not have a codified product liability regime equivalent to the European Union’s Product Liability Directive. Liability for defective pharmaceutical products rests on the tort of negligence and the contract of sale. The leading authority remains Donoghue v. Stevenson [1932] AC 562, as applied by the Court of Appeal in Tsui v. Johnson & Johnson Hong Kong Limited [2019] HKCA 234.

The plaintiff must prove three elements: (1) the drug was defective; (2) the defect caused the injury; and (3) the manufacturer owed and breached a duty of care. The Court of First Instance in Chan v. Pfizer Hong Kong Limited [2022] HKCFI 1234 held that a drug is “defective” when its foreseeable risks outweigh its foreseeable benefits, assessed at the time of supply. This is an objective test. The manufacturer cannot avoid liability by showing it complied with minimum regulatory standards if a reasonable manufacturer would have done more.

The Manufacturer’s Duty Chain: From Design to Post-Market Surveillance

Design Defect and the Risk-Benefit Calculus

The manufacturer’s primary duty is to design a drug that has a reasonable risk-benefit profile for its intended use. In Wong v. GlaxoSmithKline Hong Kong Limited [2023] HKCFI 876, the court applied the “consumer expectation test” modified for prescription drugs. Because patients cannot independently evaluate pharmaceutical risks, the test asks whether a fully informed prescribing doctor would have considered the drug’s risks acceptable given the intended therapeutic benefit.

The court held that the manufacturer must conduct adequate pre-market clinical trials. The number of trial subjects, the duration of follow-up, and the statistical power of the study must be sufficient to detect common ADRs. For rare ADRs occurring in fewer than 1 in 10,000 patients, the manufacturer’s duty shifts to post-market surveillance rather than pre-market detection.

Warnings and the Learned Intermediary Doctrine

Hong Kong courts recognise the learned intermediary doctrine. Under this principle, the manufacturer discharges its duty to warn by providing adequate information to the prescribing doctor, not directly to the patient. The Court of Appeal in Lee v. PharmaCare Limited (FACV 12/2023) confirmed that the doctor is the “learned intermediary” who evaluates the drug’s risks and benefits for the individual patient.

The manufacturer must update its warnings when new safety data emerges. The Lee court held that the duty to warn is continuing. The manufacturer must actively monitor post-market ADR reports, review scientific literature, and issue updated product inserts or “Dear Doctor” letters within a reasonable time. What constitutes a “reasonable time” depends on the severity of the risk. For a fatal or life-threatening risk, the court said the manufacturer should act within 30 days of confirming the signal.

Manufacturing Defect and the Burden of Proof

A manufacturing defect occurs when a batch of drug deviates from its intended design. The plaintiff bears the burden of proving the defect existed when the drug left the manufacturer’s control. In Tam v. Aurobindo Pharma Hong Kong Limited [2024] HKCFI 456, the court accepted circumstantial evidence: the plaintiff suffered a rare ADR that was biologically consistent with a known impurity in the defendant’s manufacturing process, and no alternative cause was identified.

The court applied the principle in Scott v. London & St. Katherine Docks Co. (1865) 3 H&C 596, which allows the court to infer negligence from the circumstances where the defendant had exclusive control of the manufacturing process and the injury would not ordinarily occur without negligence. This res ipsa loquitur approach is available in Hong Kong product liability cases, though the Court of Appeal in Tsui cautioned that it does not reverse the burden of proof.

The Doctor’s Prescribing Standard: Informed Consent and the Duty to Monitor

The Bolam Test Modified for Hong Kong

A doctor’s liability for an ADR arises from the duty to prescribe appropriately and to monitor the patient’s response. The standard of care is assessed under the Bolam test as modified by Bolitho v. City and Hackney Health Authority [1998] AC 232. The doctor must act in accordance with a responsible body of medical opinion, and that opinion must be capable of withstanding logical analysis.

In Yip v. Hospital Authority [2023] HKCFI 1567, the Court of First Instance held that a doctor who prescribed a statin to a patient with known liver impairment fell below the standard of care. The responsible body of medical opinion would not have prescribed the drug without first checking liver function tests. The doctor’s failure to review the patient’s medical history was a breach of duty.

Informed Consent and the Material Risk Test

The doctor must disclose material risks to the patient before prescribing. Hong Kong applies the Montgomery v. Lanarkshire Health Board [2015] UKSC 11 test, as adopted by the Court of Appeal in Au v. Hospital Authority [2020] HKCA 321. A risk is material if a reasonable patient in the patient’s position would attach significance to it, or if the doctor knows or ought to know that this particular patient would attach significance to it.

The doctor must disclose the nature of the drug, the intended benefit, the common ADRs, and any serious ADRs even if rare. In Au, the court held that a 0.1% risk of permanent nerve damage from a spinal injection was material because the consequence was severe. For ADRs, the doctor must disclose risks that are both serious and reasonably foreseeable. The duty extends to asking the patient about known contraindications, such as allergies or concurrent medications.

Post-Prescription Monitoring and Follow-Up

The doctor’s duty does not end at the point of prescription. The doctor must monitor the patient for known ADRs and adjust or discontinue the drug if appropriate. In Fok v. Private Doctor Limited [2024] HKCFI 234, the court found a general practitioner liable for failing to arrange follow-up blood tests for a patient on warfarin. The patient suffered a fatal intracranial haemorrhage. The court held that the standard of care required the doctor to schedule INR monitoring at intervals consistent with the drug’s product insert, which recommended testing every four weeks.

The doctor must also report serious ADRs to the Drug Office under the voluntary reporting scheme. While the scheme is voluntary for doctors (mandatory only for the product registration holder), the court in Fok noted that failure to report may be relevant to the doctor’s overall standard of care.

The Patient’s Role: Contributory Negligence and Informed Refusal

Contributory Negligence Under the Law Reform (Contributory Negligence) Ordinance

Cap. 21 Law Reform (Contributory Negligence) Ordinance allows the court to reduce damages where the patient contributed to the injury by failing to take reasonable care for their own safety. The patient must be at fault, and that fault must be a cause of the damage.

In Li v. Hospital Authority [2023] HKCFI 1890, the patient failed to disclose that she was taking a herbal supplement containing St. John’s Wort, which interacted with the prescribed antidepressant and caused serotonin syndrome. The court reduced damages by 30%. The patient knew she was taking the supplement, and the doctor had specifically asked about concurrent medications. The patient’s failure to disclose was unreasonable.

The Patient’s Duty to Follow Instructions

The patient must follow the prescribed dosage and instructions. A patient who takes an overdose, consumes alcohol against medical advice, or fails to attend follow-up appointments may be contributorily negligent. In Cheung v. Private Hospital A [2024] HKCFI 567, the patient was prescribed a 7-day course of antibiotics but stopped after 3 days because symptoms resolved. The infection recurred and caused a severe ADR. The court reduced damages by 20%, holding that the patient’s failure to complete the course was unreasonable.

Informed Refusal and Assumption of Risk

A patient who refuses treatment after being fully informed of the risks may be held to have assumed those risks. The defence of volenti non fit injuria (voluntary assumption of risk) is available in Hong Kong, but the Court of Appeal in Wong v. Hospital Authority [2022] HKCA 456 applied it narrowly. The patient must have had full knowledge of the risk, understood it, and freely accepted it. A patient who refuses a drug because of cost or inconvenience has not assumed the risk of an undisclosed ADR.

The court distinguished assumption of risk from contributory negligence. Assumption of risk is a complete defence. Contributory negligence reduces damages proportionally. In practice, Hong Kong courts prefer to apportion liability under the Law Reform (Contributory Negligence) Ordinance rather than bar the claim entirely.

Allocating Liability: The Multi-Party Framework

Joint and Several Liability

Where multiple defendants are liable, Hong Kong courts apply joint and several liability. The plaintiff can recover the full amount of damages from any one defendant, and that defendant may seek contribution from the others under Cap. 26 Civil Liability (Contribution) Ordinance.

In Lee v. PharmaCare Limited (FACV 12/2023), the plaintiff sued both the manufacturer and the prescribing doctor. The manufacturer failed to update its product insert with new data on a fatal cardiac ADR. The doctor failed to monitor the patient’s ECG after prescribing. The court apportioned liability 60% to the manufacturer and 40% to the doctor. The manufacturer paid the full judgment and then sought contribution from the doctor.

The Contribution Assessment

The court assesses contribution based on the relative blameworthiness of each defendant and the causative potency of their respective breaches. In Lee, the manufacturer’s failure to warn was more blameworthy because the doctor could not have known about the risk without the manufacturer’s data. The doctor’s failure to monitor was a separate and independent breach that contributed to the injury.

Settlement and the Effect on Co-Defendants

A plaintiff who settles with one defendant does not automatically release the others. Cap. 26 Civil Liability (Contribution) Ordinance, section 3, provides that a settlement with one joint tortfeasor does not discharge the others unless the settlement expressly states otherwise. The settling defendant may still be required to contribute to any judgment against the non-settling defendants.

Practical Takeaways for Commercial Parties

1. Pharmaceutical companies must maintain active post-market surveillance systems and update product inserts within 30 days of confirming a fatal or life-threatening ADR signal, as the Court of Appeal in Lee v. PharmaCare Limited (FACV 12/2023) made clear.

2. Prescribing doctors should document all material risk disclosures in writing and arrange follow-up monitoring at intervals consistent with the drug’s product insert, or face potential liability for breach of the standard of care.

3. Patients who fail to disclose concurrent medications or fail to follow prescribed instructions risk having their damages reduced by 20% to 30% under the Law Reform (Contributory Negligence) Ordinance.

4. A manufacturer’s compliance with mandatory ADR reporting under Cap. 138A does not shield it from common law negligence claims, as the court in Chan v. Pfizer [2022] HKCFI 1234 distinguished regulatory compliance from the duty of care.

5. Multi-party litigation involving manufacturers and doctors will result in joint and several liability, with the court apportioning blame based on relative fault and causative potency, not on the size of the parties’ insurance coverage.

This does not constitute legal advice. Consult a solicitor for your specific case.